WO2022253173A1

WO2022253173A1 - H-ngal for the detection of peritonitis

Info

Publication number: WO2022253173A1
Application number: PCT/CN2022/095940
Authority: WO
Inventors: YongSheng JI; Fangfang HUANG; Jesus Eduardo MUNOZ-SILVA; Tao Jiang
Original assignee: Fresenius Medical Care Deutschland Gmbh; Fresenius Medical Care Holdings, Inc.; Fresenius Medical Care R & D (Shanghai) Co., Ltd.
Priority date: 2021-05-31
Filing date: 2022-05-30
Publication date: 2022-12-08
Also published as: EP4348253A1; CN115715369A; CN115480061A

Abstract

A method for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising: detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis subject, if H-NGAL protein is greater than or equal to a cutoff value, indicating that the subject has or is at a risk of peritonitis. A strip, a kit and a device used in the method, and the use of a molecule that specifically binds to H-NGAL protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis by detecting H-NGAL protein in peritoneal dialysis effluent of a peritoneal dialysis subject.

Description

H-NGAL for the Detection of Peritonitis

Field of the invention

The invention relates to the diagnosis of peritonitis, in particular, to the diagnosis, in particular, quick diagnosis of peritonitis in a peritoneal dialysis subject by detecting homodimer neutrophil gelatinase-associated lipocalin (H-NGAL) in peritoneal dialysis effluent.

Background of the invention

Neutrophil gelatinase-associated lipocalin (NGAL) is a protein involved in innate immunity, and can be found in three forms in blood and urine, i.e., a 25-KD monomer mainly released by tubular cells, a 45-KD homodimer (H-NGAL) mostly synthesized by neutrophils, and a 135-KD heterodimer associated with matrix metalloproteinase 9 (MMP-9) .

NGAL is known as a marker of acute kidney injury (AKI) (Linjun Cai et al., “Assays of urine levels of HNL/NGAL in patients undergoing cardiac surgery and the impact of antibody configuration on their clinical performances” , Clinica Chimica Acta 403 (2009) 121–125, DOI: 10.1016/j. cca. 2009.01.030; Linjun Cai et al., “The origin of multiple molecular forms in urine of HNL/NAGL” , Clin J Am Soc Nephrol 5: 2229–2235, 2010, DOI: 10.2215/CJN. 00980110) , and involves in the pathological process of chronic kidney disease.

Interleukin-6 (IL-6) is a multifunctional protein produced by a wide array of cells. It increases in peritoneal dialysis effluent (PDE) before the onset of peritonitis, during peritonitis, and even after peritonitis.

Peritonitis is a common disease in peritoneal dialysis patients, and is one of the main causes leading to death of peritoneal dialysis patients and failure of peritoneal dialysis. In general, early detection and treatment would result in good prognosis of peritonitis associated with peritoneal dialysis. Generally, peritonitis is detected by means of laboratory culture (3-7 days) and imaging examination, and antibiotic treatment is adjusted according to the culture result. These methods of detecting peritonitis require specialized facilities and take a long time. There is a need in the art to find a new means to facilitate detection, especially quick diagnosis of peritonitis, so as to detect and treat peritonitis as early as possible to improve peritoneal dialysis treatment.

Summary of the invention

The invention provides a method of diagnosis, in particular quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising: detecting H-NGAL in peritoneal dialysis effluent of the subject, if H-NGAL is greater than or equal to a cutoff value, indicating that the subject has peritonitis or is at risk of peritonitis; optionally, further detecting IL-6 in the peritoneal dialysis effluent, if IL-6 is greater than or equal to a cutoff value, indicating that the subject has peritonitis or is at risk of peritonitis. By quick diagnosis of peritonitis or a risk of peritonitis, peritonitis can be detected as early as possible, thereby realizing early diagnosis and treatment.

The invention also provides a strip for diagnosis, in particular quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end, continuously comprising: a sample pad, a conjugate pad, a nitrocellulose (NC) membrane and optionally an absorbent pad, wherein the NC membrane comprises a test line and a control line, wherein: the conjugate pad comprises a first molecule that specifically binds to H-NGAL protein, optionally which is labeled; the test line comprises an immobilized substance that detects the complex formed by H-NGAL protein and the first molecule; and the control line comprises an immobilized substance that binds to the first molecule. Optionally, the conjugate pad further comprises a third molecule that specifically binds to IL-6 protein, optionally labeled, and the NC membrane further comprises another test line, which comprises an immobilized substance detecting the complex formed by IL-6 protein and the third molecule; and optionally, the control line may comprise an immobilized substance that binds to the third molecule. A strip for quick diagnosis of peritonitis or a risk of peritonitis can be used domiciliary as so to quickly and conveniently diagnose peritonitis or a risk of peritonitis, thereby realizing early diagnosis and treatment of peritonitis.

The invention also provides a strip for diagnosis, in particular quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a biotinylated pad, a gold-labeled pad, a nitrocellulose membrane and an absorbent pad, wherein the nitrocellulose membrane comprises a test line and a control line, wherein the biotinylated pad comprises a biotin-labeled first molecule that specifically binds to H-NGAL protein; the gold-labeled pad comprises a colloidal gold-labeled second molecule that specifically binds to H-NGAL protein; the test line comprises streptavidin; and the control line comprises an immobilized molecule that specifically binds to the first molecule and/or the second molecule, optionally wherein the first molecule and the second molecule are different.

The invention also provides a strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a conjugate pad, a nitrocellulose membrane and optionally an absorbent pad, wherein the conjugate pad comprises a first molecule that specifically binds to H-NGAL protein, optionally labeled, and optionally a second molecule that specifically binds to H-NGAL protein, optionally labeled; the nitrocellulose membrane comprises a test line and a control line, wherein the test line comprises an immobilized substance that detects a complex formed by H-NGAL protein and the first molecule and/or the second molecule; and the control line comprises an immobilized substance that binds to the first molecule and/or the second molecule, optionally wherein the first molecule and the second molecule are different. Optionally, the conjugate pad further comprises a third molecule that specifically binds to IL-6 protein, optionally labeled, and a fourth molecule that specifically binds to IL-6 protein, optionally labeled, and the nitrocellulose membrane further comprises another test line comprising an immobilized substance that detects a complex formed by IL-6 protein and the third molecule and/or the fourth molecule, and optionally, the control line comprises an immobilized substance that specifically binds to the third molecule and/or the fourth molecule, optionally wherein the third molecule and the fourth molecule are different.

The invention also provides a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a means for detecting H-NGAL protein, and optionally a means for detecting IL-6 protein. Optionally, the kit further comprises a reference colorimetric card, wherein a negative or positive detection result is determined according to the comparison of the result with the reference colorimetric card.

The invention also provides a device for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a part for detecting H-NGAL protein and optionally a part for detecting IL-6 protein in peritoneal dialysis effluent of the peritoneal dialysis subject.

The invention also provides use of a molecule that specifically binds to H-NGAL protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting H-NGAL protein in peritoneal dialysis effluent of a peritoneal dialysis subject. The invention also provides an in vitro test for the diagnosis, preferably quick diagnosis, of peritonitis or the diagnosis of a risk of peritonitis.

The invention also provides use of a combination of a molecule that specifically binds to H-NGAL protein and a molecule that specifically binds to IL-6 protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting H-NGAL protein and IL-6 protein in peritoneal dialysis effluent of a peritoneal dialysis subject.

The invention also provides use of a molecule that specifically binds to IL-6 protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting peritoneal dialysis effluent of a peritoneal dialysis subject in combination with a molecule that specifically binds to H-NGAL protein.

The invention also provides use of a molecule that specifically binds to H-NGAL protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting peritoneal dialysis effluent of a peritoneal dialysis subject in combination with a molecule that specifically binds to IL-6 protein.

The invention also provides a molecule that specifically binds to H-NGAL protein for use in the diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting H-NGAL protein in peritoneal dialysis effluent of a peritoneal dialysis subject.

The invention also provides a combination of a molecule that specifically binds to H-NGAL protein and a molecule that specifically binds to IL-6 protein for use in the diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting H-NGAL protein and IL-6 protein in the peritoneal dialysis effluent of a peritoneal dialysis subject.

The invention also provides a molecule that specifically binds to IL-6 protein for use in the diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting peritoneal dialysis effluent of a peritoneal dialysis subject in combination with a molecule that specifically binds to H-NGAL protein.

The invention also provides a molecule that specifically binds to H-NGAL protein for use in the diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting peritoneal dialysis effluent of a peritoneal dialysis subject in combination with a molecule that specifically binds to IL-6 protein.

The invention also provides use of a molecule that specifically binds to H-NGAL protein in the preparation of a strip for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting H-NGAL protein in peritoneal dialysis effluent of a peritoneal dialysis patient, wherein the strip has a cut-off value of 500 pg/mL for H-NGAL.

The invention also provides use of a combination of a molecule that specifically binds to H-NGAL protein and a molecule that specifically binds to IL-6 protein in the preparation of a strip for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis by detecting H-NGAL protein and IL-6 protein in peritoneal dialysis effluent of a peritoneal dialysis patient, wherein the strip has a cut-off value of 500 pg/mL for H-NGAL and a cut-off value of 200 pg/mL for IL-6.

Brief description of the drawings

Figure 1: Principle of lateral flow sandwich immunoassay

Figure 2: An exemplified reference colorimetric card

Figure 3: Schematic diagram of an assembled strip

Figure 4: Schematic structure of a colloidal gold immunochromatography strip

Figure 5: Schematic diagram of an immunochromatography strip

Figures 6-8: Some exemplified strip test results

Detailed description of the invention

Unless otherwise specified, the scientific and technical terms used herein shall have the meanings commonly known to those skilled in the art. In addition, unless specifically required, singular terms shall comprise pluralities, and plural terms shall comprise singular. The aforementioned techniques and methods are usually carried out according to conventional methods well known in the art and described in the references cited in this specification. See, for example, Sambrook et al. Molecular Cloning: A Laboratory Manual (3rd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N. Y. (2001) ) incorporated as reference. All references cited herein, including patents, patent applications, articles, textbooks, etc. and the references cited therein, are incorporated herein by reference in their entirety.

The invention provides a method, a product and a device for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient, so that peritonitis or a risk of peritonitis can be diagnosed quickly and conveniently, thereby being treated or prevented accordingly. The method, product and device of the invention are useful in quick diagnosis after the patient develops peritonitis and auxiliary diagnosis of peritonitis associated with peritoneal dialysis. A method, product and device for quick diagnosis of peritonitis or a risk of peritonitis can be employed domiciliary so as to realize quick and convenient diagnosis, thereby early detection and treatment, of peritonitis.

In one aspect, the invention provides a method for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising detecting H-NGAL protein in peritoneal dialysis effluent of the subject, if H-NGAL protein is greater than or equal to a cutoff value, indicating that the subject has peritonitis or is at a risk of peritonitis. In a further embodiment, the method further comprises detecting IL-6 protein in the peritoneal dialysis effluent, if IL-6 protein is greater than or equal to a cutoff value, indicating that the subject has peritonitis or is at a risk of peritonitis.

As used herein, the "subject" or "patient" are used interchangeably and include human and non-human mammals, such as mice, rats, sheep, cows, dogs, cats, rabbits, etc., in particular human.

As used herein, “cut-off” , “cut off” and “cutoff” values are used interchangeably, and sometimes are also called as “positive judgement” value.

Peritoneal dialysis is a process of infusing peritoneal dialysis solution into the abdominal cavity of a subject for dialysis. The peritoneal dialysis effluent is the peritoneal dialysis solution taken out from the abdominal cavity after dialysis. Peritoneal dialysis includes two types, continuous ambulatory peritoneal dialysis (CAPD) and automatic peritoneal dialysis (APD) . In ambulatory peritoneal dialysis, peritoneal dialysis solution is manually changed every several hours, for dialysis purpose. Automatic peritoneal dialysis is a peritoneal dialysis by means of an external mini-machine, in which, the machine as pre-configured automatically infuses a large volume of dialysis solution into abdominal cavity and then drains it out of the body, and this process does not need manual change of dialysis solution and can be carried out at night. For example, every country have professional documents such as “Peritoneal Dialysis Standard Operating Procedure” or the like, which details the prescription and adjustment on peritoneal dialysis and peritoneal dialysis operation.

Generally, following doctor’s discretion and prescription, a subject is subjected to peritoneal dialysis by using the volume as prescribed, e.g. about 1, 2, 3, 4, 5, 6, 7 or 8 liters of dialysis solution, every several hours, e.g. every 2, 3, 4, 5, 6, 7 or 8 hours. In this context, if not specifically indicated or otherwise determined according to the context, the peritoneal dialysis is CAPD and the volume of dialysis solution for each treatment is about 2 liters.

As recommended by the International Society for Peritoneal Dialysis (ISPD GUIDELINES/RECOMMENDATIONS, Peritoneal Dialysis International, Vol. 36, pp.481-508) , generally, for APD patients which do not subject to liquid exchange in daytime, no liquid can be drained out when there is abdominal pain. In this case, one liter of peritoneal dialysis solution needs to infuse and dwell for at least 1 to 2 hours, and then drained out to examine turbidity of effluent and perform related assays and culturing. Patients suspected of being infected or those with clear effluent but with systemic or abdominal symptoms, subject to a second exchange of peritoneal dialysis solution and have a dwell time of at least two hours prior to examination. In this context, an effluent sample from APD patients is taken according to the recommended process.

As used herein, "peritoneal dialysis effluent" (PDE) refers to the liquid that is drained out from abdominal cavity without further treatment after peritoneal dialysis with peritoneal dialysis solution of a patient subjecting to stable CAPD or APD dialysis of according to the Peritoneal Dialysis Standard Operating Procedure, i.e. after CAPD or APD. In one embodiment, the peritoneal dialysis effluent is obtained from a peritoneal dialysis solution, e.g. of 2 liters, that has been dwelled in abdominal cavity for at least 2 hours. In one embodiment, the PDE is directly used for detecting H-NGAL and/or IL-6 after drained out.

As used herein, "peritonitis" is an inflammation in abdominal cavity caused by, for example, bacterial/fungal infection, chemical irritation or injury, mainly manifested as abdominal pain, tension in the abdominal muscles, nausea, vomiting, and fever. In severe cases, it can cause a decrease in blood pressure and systemic toxic reactions, and if not treated in time, death from toxic shock.

According to ISPD GUIDELINES/RECOMMENDATIONS, Peritoneal Dialysis International, Vol. 36, pp. 481-508, peritonitis always be diagnosed when at least 2 of the following are present: (1) clinical features consistent with peritonitis, i.e. abdominal pain and/or cloudy dialysis effluent; (2) dialysis effluent white cell count >100/μL or > 0.1×10 ⁹/L (after a dwell time of at least 2 hours) ; and (3) positive dialysis effluent culture.

As used herein, "quick diagnosis" refers to diagnosis of peritonitis or a risk of peritonitis, such as within 40 minutes, 30 minutes, 25 minutes, 20 minutes, 15 minutes, 10 minutes, 8 minutes, 6 minutes, 4 minutes, 2 minutes, 1 minute or even less. "Early diagnosis" refers to diagnosis of peritonitis or a risk of peritonitis, such as within 0-4 days, 0-3 days, 0-2 days, 0-1 day, 0-24 hours, 0-18 hours, 0-12 hour, 0-11 hour, 0-10 hour, 0-9 hour, 0-8 hour, 0-7 hour, 0-6 hour, 0-5 hour, 0-4 hour, 0-3 hour, 0-2 hours, 0-1 hours or even less.

H-NGAL protein refers to the 45kD homodimer neutrophil gelatinase-related lipocalin. NGAL is a 25kDa glycosylated single-chain monomer (Genbank ID of human NGAL: CAA67574.1) and a member of the lipocalin family that binds and transports small lipophilic molecules. NGAL is released by activated neutrophils, renal tubular epithelial cells, cardiomyocytes, uterus, prostate, salivary glands and other tissues, and can be detected in serum and urine. NGAL can form dimers, including a 45kDa disulfide-linked homodimer and a 135kDa heterodimer associated with metalloprotease 9 (MMP9, gelatinase B) . In one embodiment, the NGAL is human NGAL, and the homodimer H-NGAL is human H-NGAL.

IL-6 belongs to the gp130 cytokine family. IL-6 is a protein produced from preferably a single gene encoding a 212 amino acid product, more preferably a 184 amino acid IL-6 peptide cleaved from the N-terminus of the 212 amino acid peptide (Song M, Kellum JA. Interleukin-6. Crit Care Med 2005; 33 (Suppl12) : 463-465; the NCBI accession number of the IL-6 precursor in 212 amino acid length is NP_000591) . In one embodiment, the IL-6 is human IL-6. In this context, IL-6 preferably encompasses IL-6 variants, preferably human IL-6 variants. In one embodiment, the IL-6 variant is a variant that can occur naturally in a subject, such as human, e.g. an allelic variant, a species variant and the like. Those skilled in the art know how to identify and confirm IL-6 and its variants.

In one embodiment, the cutoff value for H-NGAL protein is 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 or 10000 pg/mL, preferably 500 pg/mL.

In one embodiment, the cut-off value for IL-6 protein is 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000 pg/mL, preferably 200 pg/mL.

Herein, H-NGAL and/or IL-6 protein can be detected by any suitable method for detecting H-NGAL and/or IL-6 protein known in the art, such as chemiluminescence, biochemical methods, immunological techniques (including, e.g. enzyme-linked immunosorbent assay (ELISA) , AlphaLISA, immunoblotting, dot blotting, immunoprecipitation, colloidal gold immunochromatography, etc. ) , mass spectrometry. In one embodiment, H-NGAL and/or IL-6 protein are detected by using specific antibodies (such as monoclonal antibodies) or antigen-binding fragments thereof, ligands, aptamers and the like. In one embodiment, H-NGAL and/or IL-6 protein are detected by using specific antibodies, such as lateral flow sandwich immunoassays (e.g., strips) .

Lateral flow assay ( “LFA” ) (also known as lateral flow immunoassay ( “LFIA” ) ) is a simple and easy-to-use assay to confirm the presence or absence of target analytes, such as pathogens or biomarkers in humans or animals. Lateral flow assay typically has a control line to confirm that the test is working properly, along with one or more target or test lines. They can be qualitative and read visually, or quantitative when combined with reader technology, such as

Although a “competitive assay” could be adapted for use herein (e.g., by utilization of an enrichment method such as centrifugation to increase the sensitivity of detection) , sandwich (or “non-competitive” ) assays are typically preferred for use herein. The principle of lateral flow sandwich immunoassay can be found in figure 1. In a non-competitive immunoassay assay, typically the presence of a colored line at the test line indicates a positive test. A non-competitive immunoassay is ideal for large molecular weight analytes with multiple antigenic sites. Generally, non-competitive immunoassays have a lower limit of detection (higher analysis sensitivity) compared to a competitive format. Typically, non-competitive immunoassays can detect on the order of picograms/mL in comparison to nanograms/mL for competitive assays.

Lateral flow devices typically utilize immunoassay technology with a nitrocellulose membrane, colored latex nanoparticles (or labels such as magnetic beads or colored styrene balls) , and antibodies, for quick analysis. When a sample from a PDE is added to the lateral flow device, the sample flows along the test device passing through a conjugate pad into a nitrocellulose membrane and then onto an absorbent pad to absorb excess sample. The sample pad acts as the first stage of the absorption process, and in some cases contains a filter to ensure the accurate and controlled flow of the sample. The conjugate pad, which stores the conjugated labels and antibodies, receives the sample. If the target is present, the immobilized conjugated antibodies and labels bind to the target and continue to migrate along the test. As the sample moves along the device, the binding reagents situated on the nitrocellulose membrane bind to the target at the test line. A colored line forms and the density of the line varies depending on the quantity of the target present. Some targets may require quantification to determine the target concentration such as by using a reader. A more sophisticated system can be used to acquire quantitative data, for example, the immunofluorescence technology together with a reader may be utilized to measure the quantity of markers in PDE to provide more information to the patients and clinicians by comparing the obtained values with a predetermined cutoff value.

Multiplexed lateral flow assays, related methods, and devices are disclosed in US 20050250141A1 (Nov. 10, 2005) , the contents of which are incorporated herein by reference. US 6,924,153 B1, US 8,128,871 B2 and US 7,785,899 B2, the contents of which are incorporated herein by reference, disclose various lateral flow test kits capable of detecting multiple analytes.

For example, in colloidal gold immunochromatography, a specific antibody (or an antigen) is immobilized on the membrane in strip form, and a colloidal gold-labeled reagent (antibody) is adsorbed on the conjugate pad. When the sample to be tested is added to the sample pad at one end of the test strip, it moves forward via capillary action, dissolves the colloidal gold-labeled reagent on the conjugate pad and reacts with each other. When moving to the immobilized antibody (or antigen) area, the complex formed by the substance to be tested and the gold-labeled reagent specifically binds thereto and thus is intercepted, gathering on the test line, and the coloration result can be observed visually. Structure of a colloidal gold immunochromatography strip is schematically described in Figure 4.

As used herein, "antibody" refers to an immunoglobulin molecule usually composed of two pairs of polypeptide chains (each pair has a light chain (LC) and a heavy chain (HC) ) . "Antigen-binding fragment" , also called "antigen-binding portion" , refers to a polypeptide fragment of an antibody, such as a polypeptide fragment of a full-length antibody, which retains the specific binding ability to the same antigen that the full-length antibody binds to, and/or competes with the full-length antibody for specific binding to the antigen. See Fundamental Immunology, Ch. 7 (Paul, W., ed., 2nd edition, Raven Press, NY (1989) , which is incorporated herein by reference in its entirety. Non-limiting examples of the antigen-binding fragment comprise Fab, Fab', F (ab') ₂, Fd, Fv, dAb and complementarity determining region (CDR) fragments, single chain antibodies (such as scFv) , chimeric antibodies, diabodies, linear antibodies, nanobodies (such as the technology from Ablynx) , domain antibodies (such as the technology from Domantis) , and polypeptides comprising at least a portion of an antibody sufficient to have antigen-specific binding ability.

As used herein, "specifically bind" refers to a non-random binding reaction between two molecules, such as the reaction between an antibody and the antigen against which it is directed. The term “specifically bind, ” or “specifically recognize, ” as used herein, in reference to the interaction of an antibody and its binding partner, e.g. an antigen, means that the interaction is dependent upon the presence of a particular amino acid sequence or structure, e.g. an antigenic determinant or epitope, on the binding partner. In other words, the antibody preferentially binds or recognizes the binding partner even when the binding partner is present in a mixture of other molecules or organisms. The binding may be mediated by covalent or noncovalent interactions or a combination of both. In yet other words, the term “specifically bind” or “specifically recognize” means that the antibody is specifically immunoreactive with an antigenic determinant or epitope and is not immunoreactive with other antigenic determinants or epitopes. An antibody that specifically or immunospecifically binds to an antigen may bind to other peptides or polypeptides with lower affinity as determined by, e.g., radioimmunoassays ( “RIA” ) , enzyme-linked immunosorbent assays ( “ELISA” ) , BIACORE, or other assays known in the art. Antibodies or fragments thereof that specifically bind to an antigen may be cross-reactive with related antigens carrying the same epitope. Preferably, antibodies or fragments thereof that specifically bind to an antigen do not cross-react with other antigens.

The strength or affinity of a specific binding interaction can be represented by the dissociation equilibrium constant (KD) of the interaction. The term "KD" refers to the dissociation equilibrium constant of a specific antibody-antigen interaction, which describes the binding affinity between the antibody and the antigen. The smaller the dissociation equilibrium constant, the tighter the antibody-antigen binding, and the higher the affinity between the antibody and the antigen. In certain embodiments, an antibody that specifically binds to a certain antigen (or an antibody specific to a certain antigen) means that the antibody binds to the antigen with a KD of less than about 10 ^-8 M, for example, less than about 10 ^-8 M, 10 ^-9 M, 10 ^-10 M, 10 ^-11 M or even less. In certain embodiments, when KD ≤ 10×10 ^-8 M, the antibody or antigen-binding fragment thereof of the invention is considered to specifically bind to H-NGAL or IL-6 protein. Those skilled in the art can obtain antibodies specific for H-NGAL protein, NGAL protein and IL-6 protein.

Detection of H-NGAL protein can be carried out using any suitable method or manner. In one embodiment, H-NGAL protein is detected directly, for example, by mass spectrometry or by using H-NGAL protein specific antibodies or antigen binding fragments thereof. In another embodiment, H-NGAL protein can be detected indirectly, such as at first detecting total NGAL (for example, including the monomeric form and the homodimer form, or the monomeric form, the homodimer form and the heterodimer form) proteins, and then detecting the monomer form or the monomer form and the heterodimer form, thereby determining H-NGAL protein.

For example, an IgG1 monoclonal antibody that specifically binds to the homodimer form of NGAL but not the heterodimer form, is commercially available under “N457” from HyTest Ltd. of Turku, Finland (Cat. #4NG7-N457) . Other antibodies available from HyTest (including N308 and N432) have similar binding specificities as N457. Antibodies that bind the monomer, homodimer, and heterodimer forms of NGAL include N316, N417, N422, and N461 from HyTest Ltd. An enzyme immunoassay ( “sandwich immunoassay” ) for detection of solely the homodimer form of NGAL containing N316 as the NGAL capture antibody and N457 as the detection antibody is referenced in “Neutrophil gelatinase-associated lipocalin (NGAL) ” TechNotes, p. 2 (Jan. 2020 by HyTest Ltd. ) , the contents of which are incorporated herein by reference. Thus, in certain embodiments, the detection antibody for NGAL in an assay can be selected from the group consisting of N457, N308, N432, and any combinations thereof, while the capture antibody is selected from the group consisting of N316, N417, N422, N461, and any combinations thereof.

In one embodiment, the method for diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient according to the invention comprises:

(a) detecting H-NGAL protein in peritoneal dialysis effluent; or

(b) detecting total NGALs in peritoneal dialysis effluent, including the monomer NGAL, H-NGAL and heterodimer forms, and detecting the monomer and possibly present heterodimer forms so as to determine the amount of H-NGAL.

In one embodiment, the invention provides a method for diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient, comprising:

- obtaining a sample of peritoneal dialysis effluent of the patient;

- contacting a first molecule, such as an antibody, that specifically binds to H-NGAL protein with the sample, optionally the first molecule is immobilized on a solid support such as an ELISA plate; and

- detecting the formed complex.

- obtaining a sample of peritoneal dialysis effluent of the patient;

- contacting a first molecule, such as an antibody, that specifically binds to H-NGAL protein with the sample, optionally the first molecule is immobilized on a solid support such as an ELISA plate;

- adding a second molecule, such as an antibody, that specifically binds to H-NGAL protein, optionally labeled, such as labeled by an enzyme (such as horseradish peroxidase, alkaline phosphatase, glucose oxidase, and β-D-galactosidase) , wherein the second molecule and the first molecule bind to different epitopes on H-NGAL protein;

- optionally, adding a substance that specifically binds to the second molecule, such as an antibody against the second molecule, optionally labeled, such as labeled by an enzyme (such as horseradish peroxidase, alkaline phosphatase, glucose oxidase, and β-D-galactosidase) , and

- detecting the formed complex.

In one embodiment, the detection may be a coloration reaction known in the art, such as using the substrates o-phenylenediamine (OPD) , tetramethylbenzidine (TMB) , nitrophenylphosphate (pNPP) , diaminobenzidine (DAB) and so on.

In another embodiment, the invention provides a method for diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient, comprising:

- obtaining a sample of peritoneal dialysis effluent of the peritoneal dialysis patient;

- contacting a first antibody molecule that specifically binds to H-NGAL protein with the sample, wherein the first antibody molecule is labeled with biotin;

- adding a second antibody molecule that specifically binds to H-NGAL protein, wherein the second antibody molecule is labeled with colloidal gold, and the second antibody molecule and the first antibody molecule are different antibodies binding to different epitopes on H-NGAL protein, and optionally, the first antibody molecule and the second antibody molecule are independently selected from N316 and N457;

- adding streptavidin, wherein streptavidin is immobilized on a solid support such as nitrocellulose, and

- detecting the formed complex.

In one embodiment, the first molecule and the second molecule that specifically bind to H-NGAL protein are antibodies independently selected from N316 and N457 (Hytest Biotechnology (Shanghai) Co., Ltd. ) . In one embodiment, the first molecule is antibody N457 and the second molecule is antibody N316.

In a further embodiment, the method for diagnosis of peritonitis or a risk of peritonitis further comprises detecting IL-6 protein in the peritoneal dialysis effluent sample. Means for detecting IL-6 is known in the art, such as anti-IL-6 antibodies, including polyclonal and monoclonal antibodies and fragments thereof, such as M-BE8 (EP0430193; KLEIN, B., et al. 1991, Murine anti-interleukin 6 monoclonal antibody therapy for a patient with plasma cell leukemia, Blood 78, 1198-1204) or M-23C7, or an antibody that binds to the epitope they recognize.

The concentration of a protein in peritoneal dialysis effluent can be determined according to any suitable method known in the art, for example, including but not limited to, chemiluminescence, biochemical methods, affinity chromatography, immunoblotting and mass spectrometry. Methods for determining the concentration of a particular protein in a sample are well known to those skilled in the art.

It is also possible to detect whether an analyte (such as H-NGAL and/or IL-6 protein) in a sample is greater than or equal to a cutoff value by using a strip, for example, a strip having a desired cut-off value. Skilled persons in the art know how to prepare a strip as described herein, for example, a strip with a specific cut-off value.

In some embodiments, H-NGAL and/or IL-6 proteins in peritoneal dialysis effluent are detected by a strip with a given cut-off value (for example, 500 pg/mL for H-NGAL protein; 200 pg/mL for IL-6 protein) , and based detection results, to determine whether H-NGAL and/or IL-6 proteins in the peritoneal dialysis effluent are greater than or equal to cutoff values.

In one aspect, the invention provides a method of treating peritonitis in a peritoneal dialysis subject, comprising: detecting H-NGAL protein in a peritoneal dialysis effluent of the subject; determining a level of H-NGAL; comparing the level of H-NGAL against a cutoff value; and administering antibiotic therapy if the level of H-NGAL exceeds the cutoff value.

In one embodiment, the invention provides a method of treating peritonitis in a peritoneal dialysis subject, comprising: detecting H-NGAL protein and IL-6 protein in a peritoneal dialysis effluent of the subject; determining a level of H-NGAL and a level of IL-6; comparing the level of H-NGAL and the level of IL-6 against cutoff values; and administering antibiotic therapy if both the level of H-NGAL and the level of IL-6 exceed the cutoff values.

The cutoff value for H-NGAL and the cutoff value for IL-6 are described as herein. In one embodiment, the cutoff value for H-NGAL protein is 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 or 10000 pg/mL, preferably 500 pg/mL. In one embodiment, the cut-off value for IL-6 protein is 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000 pg/mL, preferably 200 pg/mL.

The antibiotic therapy may be a single agent antibiotics or combination therapy antibiotics. In one embodiment, the single agent antibiotics include ertapenem (INVANZ ^TM) , cefoxitin, doripenem (DORIBAX ^TM) , imipenem/cilastatin (PRIMAXIN ^TM) , meropenem (MERREM ^TM) , moxifloxacin (AVELOX ^TM) , piperacillin/tazobactam (ZOSYN ^TM) , ticarcillin/clavulanate (TIMENTIN ^TM) and tigecycline (TYGACIL ^TM) . In one embodiment, the combination therapy antibiotics include cefepime (MAXIPIME ^TM) , cefotaxime (CLAFORAN ^TM) , ceftazidime (FORTAZ ^TM) or ceftriaxone (ROCEPHIN ^TM) , together with metronidazole (FLAGYL ^TM) ; or cefazolin, cefotaxime, ceftriaxone, ciprofloxacin (CIPRO ^TM) , levofloxacin (LEVAQUIN ^TM) , together with metronidazole; or cefepime, ceftazidime, ciprofloxacin, levofloxacin, together with metronidazole; or gentamicin or tobramycin together with clindamycin (CLEOCIN ^TM) or metronidazole (with or without ampicillin) .

In one aspect, the invention provides a strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient, comprising a solid support having a first end and a second end, and from the first end, continuously comprising: a sample pad, a conjugate pad, a nitrocellulose membrane (comprising a test line and a control line) and optionally an absorbent pad (such as shown in Figure 5) , wherein the conjugate pad comprises a first molecule, optionally labeled, that specifically binds to H-NGAL protein; the test line comprises an immobilized substance that detects a complex formed by H-NGAL protein and the first molecule; and the control line comprises an immobilized substance that specifically binds to the first molecule. In a further embodiment, in the strip, the conjugate pad further comprises a third molecule, optionally labeled, that specifically binds to IL-6 protein, and the nitrocellulose membrane further comprises another test line comprising a substance that detects a complex formed by IL-6 protein and the third molecule, and the control line may comprise a substance that binds to the first molecule and/or the third molecule.

In one embodiment, from the first end, the solid support continuously comprises a sample pad, a conjugate pad, a nitrocellulose membrane (comprising a test line and a control line) , and an absorbent pad.

In one aspect, the invention provides a strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a biotinylated pad, a gold-labeled pad, a nitrocellulose membrane and an absorbent pad, wherein the nitrocellulose membrane comprises a test line and a control line, wherein: the biotinylated pad comprises a biotin-labeled first molecule that specifically binds to H-NGAL protein; the gold-labeled pad comprises a colloidal gold-labeled second molecule that specifically binds to H-NGAL protein; the test line comprises immobilized streptavidin; and the control line comprises an immobilized substance that specifically binds to the first molecule and/or the second molecule, optionally wherein the first molecule and the second molecule are different.

As used herein, a sample to be tested is applied to the sample pad, and the sample pad can be prepared according to any suitable method known in the art.

As used herein, the conjugate pad comprises a capture molecule, optionally labeled, that binds to the molecule to be detected in a sample.

As used herein, the biotinylated pad comprises a biotinylated molecule that specifically binds to the molecule to be detected in a sample. As used herein, the gold-labeled pad comprises a colloidal gold-labeled molecule such as an antibody that specifically binds to the molecule to be detected or a complex formed by the molecule to be detected and a capture molecule. See areas B and D shown in Figure 3.

As used herein, the nitrocellulose membrane comprises one or more test lines that contain immobilized detection molecules that bind to a complex formed by the molecule to be detected and a capture molecule. There is a distance between two test lines, e.g. a distance of 0.5-5 mm, such as 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 mm, so as not to interfere with detection results each other. How to set test lines in a strip is known in the art.

As used herein, the control line confirms whether the test is effective. The control line is separated from the test line by a certain distance, for example, of 0.5-5 mm, such as 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 mm, which can implement the test and judge whether the test is effective. How to set the control line and the test line is known in the art.

As used herein, the absorbent pad allows a liquid to flow on other pads by absorbing the liquid and/or absorbs excess sample.

As used herein, the word “continuously” means that adjacent areas are in contact each other, preferably overlap, so that the sample can spread from one to the adjacent. Those skilled in the art can determine how much they overlap according to the technical knowledge in the art, for example, with 0.5-4.0 mm, such as 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, or 4.0 mm.

For example, the strip may have at least one of the following characteristics: (a) the sample pad overlaps with the conjugate pad, wherein preferably the sample pad is above the conjugate pad; (b) the conjugate pad overlaps with the nitrocellulose membrane, wherein preferably the conjugate pad is above the nitrocellulose membrane; and (c) the nitrocellulose membrane overlaps with the absorbent pad, wherein the absorbent pad is above the nitrocellulose membrane. Further, when a biotinylated pad and a gold-labeled pad are present, the strip can also have at least one of the following characteristics: (d) the biotinylated pad overlaps with the gold-labeled pad, wherein preferably the biotinylated pad is above the gold-labeled pad; and (e) the gold label pad overlaps with the nitrocellulose membrane, wherein preferably the gold label pad is above the nitrocellulose membrane.

As used herein, the molecule that specifically binds to H-NGAL or IL-6 protein is any suitable molecule that specifically binds to H-NGAL or IL-6 protein, including, for example, antibodies (preferably monoclonal antibodies) or antigen-binding fragments thereof, ligands, aptamers and so on. Antibodies that can specifically bind to H-NGAL or IL-6 protein are known in the art.

As used herein, the label is any molecule or means that can be used to label H-NGAL and/or IL-6 protein, including for example but not limited to, biotin, fluorescence, radioactivity, luminescence, chemistry, enzyme and particulate labels such as latex particles, colloidal gold, etc. In one embodiment, the label is selected from the group consisting of colloidal gold label and biotin label.

As used herein, the substance for detecting a complex is a suitable substance that indicates the presence or absence of the complex, for example, including but not limited to antibodies or antigen-binding fragments thereof, ligands, aptamers, preferably selected from the group consisting of polyclonal antibodies, monoclonal antibodies, humanized antibodies, human antibodies, chimeric antibodies or antigen-binding fragments thereof, more preferably monoclonal antibodies or antigen-binding fragments thereof. A person skilled in the art can select a suitable substance for detecting a complex according to the technical knowledge in the art. For example, where the label is an enzyme label, the substance can be a substrate of the enzyme, which is catalyzed by the enzyme to produce a signal that can be observed (for example, visually or by a detection device) , such as coloration, luminescence, fluorescence, etc.; where the label is colloidal gold, an isotope, luminescence, etc., the substance may be a substance that binds to, for example specifically binds to, the complex or a molecule of the complex, for example an antibody, or a substance that binds to the label on the molecule, for example an antibody, so that the presence or absence of the complex can be determined by detecting signals emitted by the label. In one embodiment, the label is biotin, and the substance for detecting complex is streptavidin.

In one embodiment, the invention provides a strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a conjugate pad, a nitrocellulose membrane and an absorbent pad, wherein the conjugate pad comprises a first molecule, optionally labeled, that specifically binds to H-NGAL protein and a second molecule, optionally labeled, that specifically binds to H-NGAL protein; the nitrocellulose membrane comprises a test line and a control line, wherein the test line comprises an immobilized substance that detects a complex formed by H-NGAL protein and the first molecule and/or the second molecule; and the control line comprises an immobilized substance that binds to the first molecule and/or the second molecule, optionally wherein the first molecule and the second molecule are different. In a further embodiment, in the strip, the conjugate pad further comprises a third molecule, optionally labeled, that specifically binds to IL-6 protein and a fourth molecule, optionally labeled, that specifically binds to IL-6 protein, and the nitrocellulose membrane further comprises another test line comprising an immobilized substance that detects a complex formed by IL-6 protein and the third molecule and/or the fourth molecule, and optionally the control line comprises an immobilized substance that specifically binds to the third molecule and/or the fourth molecule, optionally wherein the third molecule and the fourth molecule are different.

In one embodiment, the invention provides a strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising: a sample pad, a conjugate pad, a nitrocellulose membrane and optionally an absorbent pad, wherein the nitrocellulose membrane comprises a test line and a control line, wherein:

the conjugate pad comprises:

(a) a first molecule, optionally labeled, that specifically binds to H-NGAL protein, and optionally, a second molecule, optionally labeled, that specifically binds to H-NGAL protein, optionally the first molecule and the second molecule are different;

(b) a third molecule, optionally labeled, that specifically binds to IL-6 protein, and optionally, a fourth molecule, optionally labeled, that specifically binds to IL-6 protein, optionally the third molecule and the fourth molecule are different;

the test line comprises a test line comprising an immobilized substance that detects a complex formed by H-NGAL protein and the first molecule and/or the second molecule, and a test line comprising an immobilized substance that detects a complex formed by IL-6 protein and the third molecule and/or the fourth molecule, and

the control line comprises an immobilized substance that specifically binds to the first molecule, the second molecule, the third molecule, and/or the fourth molecule.

In one embodiment, the invention provides a strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a biotinylated pad, a gold-labeled pad, a nitrocellulose membrane and an absorbent pad, wherein the biotinylated pad comprises a biotin-labeled first antibody molecule that specifically binds to H-NGAL protein; the gold-labeled pad comprises a colloidal gold-labeled second antibody molecule that specifically binds to H-NGAL protein; the nitrocellulose membrane comprises a test line and a control line, wherein the test line comprises immobilized streptavidin and the control line comprises an immobilized secondary antibody molecule, for example an anti-IgG antibody molecule, that binds to the first antibody molecule and/or the second antibody molecule, wherein the first antibody molecule and the second antibody molecule are different. In one embodiment, the biotinylated first antibody molecule is antibody N457 (HyTest) , and the colloidal gold-labeled second antibody molecule is antibody N316 (HyTest) . In a further embodiment, in the strip, the biotinylated pad further comprises a third antibody molecule, optionally labeled with a label other than biotin, that specifically binds to IL-6 protein; the gold-labeled pad further comprises a fourth antibody molecule, optionally labeled, such as colloidal gold-labeled, that specifically binds to IL-6 protein; and the nitrocellulose membrane further comprises another test line which comprises an immobilized substance for detecting a complex formed by IL-6 protein and the third molecule and/or the fourth molecule; and the control line may comprise an immobilized substance, for example an anti-IgG antibody molecule, that binds to the third antibody molecule and/or the fourth antibody molecule, optionally wherein the third antibody molecule and the fourth antibody molecule are different.

Methods and suitable materials for preparing respective parts of a strip (e.g. solid support, sample pad, conjugate pad, biotinylated pad, gold-labeled pad, nitrocellulose membrane, and absorbent pad) are known in the art. See e.g. Gong Pin et al., "Research progress of colloid gold immunochromatographic test strip technology and its application in food safety testing" , Food Industry Science and Technology, 2019, 40 (13) : 358-364, Article ID: 1002-0306 (2019) 13-0358-07; and Yan Lingzhi, "Research progress of immunochromatographic test strip technology in the field of food safety testing" , Food Industry Science and Technology, DOI: 10.13386/j. issn1002-0306.2020110079.

In one embodiment, the strip has a cut-off value described herein, for example, the cut-off value for H-NGAL protein can be 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 or 10000 pg/mL, and/or the cut-off value for IL-6 protein can be 50, 60, 70, 80, 90, 100, 200, 300, 400, 200, 250, 300 , 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000 pg/mL. In one embodiment, the cut-off value for H-NGAL protein is 100, 200, 300, 400, 500 pg/mL, preferably 500 pg/mL. In one embodiment, the cut-off value for IL-6 protein is 50, 60, 70, 80, 90, 100, 150, 200 pg/mL, preferably 200 pg/mL.

A person skilled in the art knows how to prepare a strip having a desired cutoff value according to the technical knowledge in the art, e.g. by obtaining an analyte solution with a given concentration by diluting a commercially purchased or prepared standard solution of the analyte with a known concentration; or determining the concentration of an analyte solution by using a quantitative method for such analyte known in the art; preparing strips having various contents or concentrations of a detection molecule specifically binding to such analyte; and determining the content or concentration of the detection molecule in the strip having a desired cutoff value, based on the test results.

In one aspect, the invention provides a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient, comprising a means for detecting H-NGAL protein, for example a molecule that specifically binds to H-NGAL protein, such as an antibody or an antigen-binding fragment thereof, and optionally a means for detecting IL-6 protein, for example a molecule that specifically binds to IL-6 protein, such as an antibody or an antigen-binding fragment thereof, and optionally a reference colorimetric card (which can used in automatic reading) , by comparing a test result to which, determining whether the result is negative or positive.

In one embodiment, the kit comprises a strip according to the invention.

In one aspect, the invention provides a device for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a part for detecting H-NGAL protein and optionally a part for detecting IL-6 protein in peritoneal dialysis effluent of a peritoneal dialysis subject, and optionally a part for displaying test results.

In one embodiment, the device comprises a part indicating that the subject has or is at risk of peritonitis when H-NGAL protein in the peritoneal dialysis effluent is greater than or equal to a cutoff value, for example, when its concentration is greater than or equal to a cut-off value of 500 pg/mL as described herein, such as a part giving a particular signal, e.g. an acoustic or visual signal, such as an electronic display.

In one embodiment, the device can be connected to a digital processing device (e.g. a personal data assistant or smartphone, a notebook computer, a desktop computer, a tablet computer or device, a remote network server, or so forth) so as to warn the patients or related personnel of the infection or the risk of infection.

In one embodiment, the device comprises a part indicating that the subject has or is at a risk of peritonitis when H-NGAL protein in the peritoneal dialysis effluent is greater than or equal to a cutoff value (for example its concentration is greater than or equal to a cut-off value of 500 pg/mL as described herein) and IL-6 protein in the peritoneal dialysis effluent is greater than or equal to a cutoff value (for example its concentration is greater than or equal to a cut-off value of 200 pg/mL as described herein) .

As used herein, the part for detecting H-NGAL protein and/or IL-6 protein can be any suitable unit or apparatus capable of detecting, preferably quantifying, the protein, including for example strips, protein arrays, mass spectrometers and the like.

In one embodiment, the device comprises a strip and/or a kit as described herein.

As used herein, the part for displaying test results can inform the subject or relevant medical personnel of the test results (for example, negative or positive, or specific values, etc. ) in any suitable way (for example, beep, digital signal, networked message, etc. ) , including for example a display screen and the like.

The device can be intercommunicated with other systems, including but not limited to smart phones, tablet computers, notebook computers, and a combination of computing equipment and cloud computing resources.

The embodiments of the devices and the methods described herein can be implemented in various systems, including but not limited to smart phones, tablet computers, notebook computers, and a combination of a computing device and a cloud computing resource. For example, some operations can run in one device, while others in remote locations, such as one or more remote servers. For example, data collection is carried out on a smart phone, and data analysis on a server or cloud computing resource. Any single computing device or combination of computing devices can perform the method.

In another aspect, the invention provides a molecule that specifically binds to H-NGAL protein as described herein for use in diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis patient.

In another aspect, the invention provides a molecule that specifically binds to H-NGAL protein in combination with a molecule that specifically binds to IL-6 protein as described herein for use in diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting H-NGAL and IL-6 proteins in peritoneal dialysis effluent of the peritoneal dialysis patient.

In another aspect, the invention provides use of a molecule that specifically binds to H-NGAL protein as described herein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis patient.

In another aspect, the invention provides use of a combination of a molecule that specifically binds to H-NGAL protein and a molecule that specifically binds to IL-6 protein as described herein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting H-NGAL protein and IL-6 protein in peritoneal dialysis effluent of the peritoneal dialysis patient.

In another aspect, the invention provides use of a molecule that specifically binds to IL-6 protein as described herein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting peritoneal dialysis effluent of the peritoneal dialysis patient in combination with a molecule that specifically binds to H-NGAL protein.

In another aspect, the invention provides use of a molecule that specifically binds to H-NGAL protein as described herein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting peritoneal dialysis effluent of the peritoneal dialysis patient in combination with a molecule that specifically binds to IL-6 protein.

In another aspect, the invention provides use of a molecule that specifically binds to H-NGAL protein as described herein in the preparation of a strip for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis patient, wherein the strip has a cut-off value for H-NGAL selected from the group consisting of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 and 10000 pg/mL. In one embodiment, the strip has a cutoff value of 500 pg/mL for H-NGAL.

In another aspect, the invention provides use of a combination of a molecule that specifically binds to H-NGAL protein and a molecule that specifically binds to IL-6 protein as described herein in the preparation of a strip for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient by detecting H-NGAL protein and IL-6 protein in peritoneal dialysis effluent of the peritoneal dialysis patient, wherein the strip has a cut-off value for H-NGAL selected from the group consisting of 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 and 10000 pg/mL and a cut-off value for IL-6 selected from the group consisting of 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 and 1000 pg/mL. In one embodiment, the strip has a cut-off value of 500 pg/mL for H-NGAL and a cut-off value of 200 pg/mL for IL-6.

In certain embodiments, a molecule that specifically binds to H-NGAL protein is selected from the groups consisting of antibodies N457, N308, N432 and any combination thereof.

Unless otherwise explicitly indicated in the context, the word "or" intends to comprise "and" ; and the word "comprise" or “include” does not exclude other elements or steps.

As used herein, "optional" or "optionally" refers to the occurrence or non-occurrence of the event or situation described in the following, and this description comprises the occurrence and the non-occurrence of the event or situation. For example, an optional step refers to the presence or the absence of the step.

As used herein, the term "about" refers to a range of values that comprises specific values, and those skilled in the art can reasonably regard it to be similar to the specific values. In embodiments, the term "about" means within the standard error using a measurement generally accepted in the art. In embodiments, "about" refers to +/-10%or 5%of the specified values.

Those skilled in the art will understand that without departing from the spirit and scope of the invention, those skilled in the art can make any modifications or changes to the embodiments of the invention, and such modifications and changes are also within the scope of the invention. The above-mentioned embodiments are merely illustrative of the invention, and do not intend to limit the invention. The scope of the invention is defined by the appended claims. In view of the specification and common knowledge in the field, a person of ordinary skill in the art can clearly understand the scope defined by the claims.

Example

The invention is further illustrated by the following examples, but any examples or combinations thereof should not be construed as limiting the scope or embodiments of the invention.

Example 1: Manufacture of strips

1. Material

Control line: Goat-anti-rabbit IgG antibody, purchased from Shandong Shuojing Biological Co., Ltd. (Cat. No: P1303)

Test line: Streptavidin, purchased from Hangzhou Kuaige Technology Co., Ltd. (Cat. No: KYSA-003)

Antibodies:

- H-NGAL antibodies (Cat. No: N316 and N457) , purchased from Hytest Biotechnology (Shanghai) Co., Ltd.

- IL-6 antibodies (Cat. No: DA011 and DA012) , purchased from Novoprotein

- NGAL antibodies (Cat. No: 4C10A7 and 5A9D12) , purchased from NanJing GenScript

Biotin, purchased from Thermo Fisher Scientific (Cat. No: 21312)

2. Strip Preparation

2.1 Sample pad

50 mL of glass fiber treatment solution (adding 24g tris (hydroxymethyl) aminomethane, 50g sucrose, 5g trehalose, 15g casein, 5g polyvinylpyrrolidone, 3.5g anhydrous sodium carbonate and 1g NaN ₃ in order, and dissolving completely by stirring; adding 2mL of triton X-100 and mixing completely by stirring; adding appropriate amount of hydrochloric acid to adjust pH to 8.5; and placing at room temperature for use) was poured into a stainless steel dish, and a piece of glass fiber (Ahlstrom, Cat. No: 8964) was put therein, completely saturated and then taken out. The glass fiber was put on a grid, and fully dried at a temperature of 30-40℃ at an ambient humidity of <20%for 12 hours to obtain a full piece of sample pad and cut according to requirement of product.

2.2 Coating and drying of the nitrocellulose membrane

Control line: fixed spraying amount (1μL/cm) , the nitrocellulose membrane was coated with 1.5mg/mL of the goat anti-rabbit IgG antibody.

Test line: fixed spraying amount (1μL/cm) , the nitrocellulose membrane was coated with 1.0mg/mL of streptavidin.

The control line and the test line were separated by about 5mm.

Drying process: temperature of 30-40℃, dried for 2 hours.

2.3 Gold-labeled pad

10 μL of K ₂CO ₃ solution at 1%mass concentration and 20 μg of an antibody (H-NGAL antibody (Cat. No: N316) ; IL-6 antibody (Cat. No: DA011) ; and NGAL antibody (Cat. No: 4C10A7) were added into 1 ml of colloidal gold solution (four ten thousandths of nano-gold, particle size 35nm) . The gold-labeled antibody was concentrated by centrifugation at 10: 1, and the concentrated gold-labeled antibody solution was diluted at a ratio of 10%-12%; then it was uniformly immobilized on the glass fiber and dried at a temperature of 30-40℃ for 12 hours. The gold-labeled antibody reaction membrane was cut into a width of 5 mm for use.

2.4 Biotinylated pad

The coating antibodies (H-NGAL antibody (Cat. No: N457) ; IL-6 antibody (Cat. No: DA012) ; NGAL antibody (Cat. No: 5A9D12) ) were biotinylated with biotin at a molar ratio of 1: 20. After reacting at 2-8℃ in the dark for 2h, the unreacted biotins were removed via dialysis. The biotinylated antibody solution was diluted at a ratio of 0.35%-0.5%, evenly immobilized on the glass fiber, and dried at a temperature of 30-40℃ for 12 hours, and then the dried biotin antibody reaction membrane was cut into a width of 5mm for use.

2.5 Assembly

The following were placed on a baseplate: the prepared nitrocellulose membrane, then the upper absorbent paper (partially overlapped with the nitrocellulose membrane (about 1.0-1.5mm) and above it) , and then the gold-labeled pad (partially overlapped with the nitrocellulose membrane (about 1.0-1.5mm) and above it) , followed by the biotinylated pad (partially overlapped with the gold-labeled pad (about 1.0-1.5mm) and above it) , and finally the sample pad obtained in 2.1 (partially overlapped with the biotinylated pad (about 1.0-1.5mm) and above it) . The prepared strips from one end to the other comprises: the upper absorbent paper, the nitrocellulose membrane (sequentially the control line and the test line) , the gold-labeled pad, the biotinylated pad, and the sample pad (with sample loading wells thereon) . The assembled test strip is shown in Figure 3.

Finally, handle stickers, MAX tape (strip type) and white stickers (card type, pen type) were attached, and then cut into the required width of the reagent, and stored at 4℃-30℃ in the dark.

3. Preparation of standards of NGAL, IL-6 and H-NGAL

NGAL (recombinant neutrophil gelatinase-associated lipocalin antigen (monomer) ) : Shandong Shuojing Biological Co., Ltd., Cat. No: 190703

H-NGAL (recombinant neutrophil gelatinase-associated lipocalin antigen (Homodimer) ) : Nanjing AIDPRO Biotech Technology Co., Ltd., Cat. No: AEP0061

IL-6 (interleukin 6) : NIBSC, Cat. No: 89-548

The respective standards of NGAL, IL-6 and H-NGAL were diluted in series with negative peritoneal dialysis effluent sample to obtain NGAL, IL-6 and H-NGAL solutions of various concentrations. The solutions of different concentrations were assayed by strips having different cutoff values, and each concentration was repeated not less than 3 times.

Example 2: Diagnosis and assay of peritonitis

1. According to ISPD guidelines (ISPD GUIDELINES/RECOMMENDATIONS, ISPD PERITONITIS RECOMMENDATIONS: 2016 UPDATE ON PREVENTION AND TREATMENT, Peritoneal Dialysis International, Vol. 36, pp. 481–508) , peritonitis in patients are diagnosed when at least 2 of the following are present: (1) clinical features consistent with peritonitis, i.e. abdominal pain and/or cloudy dialysis effluent; (2) dialysis effluent white cell count > 100/μL or > 0.1×10 ⁹/L (after a dwell time of at least 2 hours) with > 50%polymorphonuclear leukocytes (PMN) ; and (3) positive dialysis effluent culture.

Peritonitis in peritoneal dialysis patients were diagnosed according to the above criteria. Peritoneal dialysis includes two types, continuous ambulatory peritoneal dialysis (CAPD) and automatic peritoneal dialysis (APD) . Following the doctor’s discretion and prescription, the subjects were subject to peritoneal dialysis by using the volume of peritoneal dialysis solution as prescribed every several hours. As described above, peritoneal dialysis was performed according to the ISPD guidelines (ISPD GUIDELINES/RECOMMENDATIONS, Peritoneal Dialysis International, Vol. 36, pp. 481–508) .

2. Detection method

2.1 Obtaining samples of peritoneal dialysis effluent from peritoneal dialysis patients

2.2 Adding 70-80μL (2 drops) of the peritoneal dialysis effluent sample to the sample loading wells of the strips as prepared in Example 1, and reacting for 10-15 minutes

2.3 Comparing the strips with the reference colorimetric card (as shown in Figure 2) , and reading the coloration results, where a coloration intensity of ≥ 0.5 is positive. Negative result = positive control line + negative test line; positive result =positive control line + positive test line. Some of the results can be seen in Figure 6-8.

3. Detection and results

3.1 IL-6 and NGAL (total NGALs, including the monomer, homodimer and heterodimer forms) proteins were detected blindly in the peritoneal dialysis effluents of peritoneal dialysis patients suffering from peritonitis and clinically diagnosed to be free of peritonitis. The information is summarized in Table 1 below.

Table 1

The detection results of the samples in Table 1 are shown in Table 2.

According to the results in Table 2, for detecting NGAL, the cutoff value of 120 ng/mL shows better specificity (87.5%) and sensitivity of 90.0%; for detecting IL-6, the cutoff value of 200 pg/mL shows sensitivity of 100%, which is better than those of the other two cutoff values, and specificity of 96.1%which is slightly lower than those of the other two cutoff values. In contrast, both specificity and sensitivity of detecting NGAL are lower than those of detecting IL-6.

3.2 H-NGAL, IL-6 and NGAL (total NGALs, including the monomer, homodimer and heterodimer forms) were detected blindly in the peritoneal dialysis effluents of peritoneal dialysis patients suffering from peritonitis and clinically diagnosed to be free of peritonitis. The information is summarized in Table 3 below.

Table 3

The detection results of the samples in Table 3 are shown in Table 4.

Detection of H-NGAL (500 pg/mL) (sensitivity of 98.18%, specificity of 96.08%) and detection ( "AND" ) of both H-NGAL (500 pg/mL) and IL-6 (200 pg/mL) (sensitivity of 98.18%, specificity of 97.87%) showed high sensitivity and specificity.

4. Conclusion

a) According to the results in Tables 2 and 4, the cutoff value for total NGAL is determined as 120 ng/mL, that for IL-6 as 200 pg/mL, and that for H-NGAL as 500 pg/mL.

b) The results in Table 4 show that detection of H-NGAL showed higher specificity and sensitivity than detection of total NGAL; detection of H-NGAL showed higher specificity than detection of IL-6.

c) Detection of H-NGAL (500 pg/mL) (sensitivity of 98.18%, specificity of 96.08%) and detection of both H-NGAL (500 pg/mL) and IL-6 (200 pg/mL) ( "AND” ) (sensitivity of 98.18%, specificity of 97.87%) showed high sensitivity and specificity.

Example 3: Further experiments of diagnosis and assay of peritonitis

According to the methods of Example 2, further diagnosis and assay of peritonitis were performed. The results are shown in the following tables.

According to the results in the table 5, it can be seen that the Sensitivity and Specificity of H-NGAL testing were improved due to the extension of the sample size, while the Sensitivity and Specificity, especially the Specificity, of IL-6 testing were reduced due to more false positive and false negative samples.

Table 5

Example 4: Different methods or reagents were compared and analyzed with clinical diagnosis results

To compare the performance of different methods of diagnosis of peritonitis, the following three methods or reagents were compared and analyzed with clinical diagnosis results.

1. WBC count

2. IL-6 (200pg/ml) POCT (point-of-care testing) prototype

3. H-NGAL (500pg/ml) POCT prototype

According to ISPD guidelines (ISPD GUIDELINES/RECOMMENDATIONS, ISPD PERITONITIS RECOMMENDATIONS: 2016 UPDATE ON PREVENTION AND TREATMENT, Peritoneal Dialysis International, Vol. 36, pp. 481–508) , peritonitis in patients are diagnosed when at least 2 of the following are present: (1) clinical features consistent with peritonitis, i.e. abdominal pain and/or cloudy dialysis effluent; (2) dialysis effluent white cell count > 100/μL or > 0.1×10 ⁹/L (after a dwell time of at least 2 hours) with > 50%polymorphonuclear leukocytes (PMN) ; and (3) positive dialysis effluent culture.

WBC counting was considered as positive if the dialysis effluent white cell count ≥ 100 cells/μL with > 50%polymorphonuclear leukocytes (PMN) , and as negative if the dialysis effluent white cell count <100 cells/μl, after a dwell time of at least 2 hours.

The IL-6 testing and the H-NGAL testing were carried out as in the Example 2.

Four-table analysis of table 6 was used for qualitative product statistical analysis, and sensitivity and specificity are calculated as follows. According to the results as shown in the following tables, the WBC counting and H-NGAL testing are very close in the performance, and there is a potential to replace WBC counting by H-NGAL testing.

Table 6

Sensitivity=a/ (a+ c) ×100%, 95%confidence interval

Specificity=d/ (b + d) ×100%, 95%confidence interval

PPV=a/ (a+ b) *100%, 95%confidence interval

NPV=d/ (c + d) *100%, 95%confidence interval

Table 7: WBC count and Clinical diagnosis analysis

Sensitivity=74/76×100%=97.37%, 95%CI (90.90-99.28%)

Specificity=128/129×100%=99.22%, 95%CI (95.74-99.86%)

PPV=74/75×100%=98.67%

NPV=128/130×100%=98.46%

Table 8: H-NGAL (500pg/ml) POCT prototype and Clinical diagnosis analysis

Sensitivity=75/76×100%=98.68%, 95%CI (92.92-99.77%)

Specificity=127/129×100%=98.45%, 95%CI (94.52-99.57%)

PPV=75/77×100%=97.40%

NPV=127/128×100%=99.22%

Table 9: IL-6 (200pg/ml) POCT prototype and Clinical diagnosis analysis

Sensitivity=72/76×100%=94.74%, 95%CI (87.23-97.93%)

Specificity=111/129×100%=86.05%, 95%CI (79.02-90.99%)

PPV=72/90×100%=80.00%

NPV=111/115×100%=96.52%

Table 10: Performance of WBC, IL-6 and H-NGAL comparation with clinical diagnosis results

Claims

Use of a molecule that specifically binds to homodimer neutrophil gelatinase-associated lipocalin (H-NGAL) in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject by detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis subject.
Use of a combination of a molecule that specifically binds to H-NGAL protein and a molecule that specifically binds to interleukin-6 (IL-6) protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject by detecting H-NGAL protein and IL-6 protein in peritoneal dialysis effluent of the peritoneal dialysis subject.
Use of a molecule that specifically binds to IL-6 protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject by detecting peritoneal dialysis effluent of the peritoneal dialysis subject in combination with a molecule that specifically binds to H-NGAL protein.
Use of a molecule that specifically binds to H-NGAL protein in the preparation of a composition, a strip or a kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject by detecting peritoneal dialysis effluent of the peritoneal dialysis subject in combination with a molecule that specifically binds to IL-6 protein.
A molecule that specifically binds to H-NGAL protein for use in the diagnosis, preferably quick diagnosis, of peritonitis or a risk of peritonitis in a peritoneal dialysis subject by detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis subject.
Use of any one of claims 1 to 5, wherein the molecule is selected from the group consisting of an antibody or an antigen-binding fragment thereof, a ligand and an aptamer, preferably from the group consisting of a polyclonal antibody, a monoclonal antibody, a humanized antibody, a human antibody, a chimeric antibody and an antigen-binding fragment thereof, more preferably from the group consisting of a monoclonal antibody and an antigen-binding fragment thereof.
Use of a molecule that specifically binds to H-NGAL protein in the preparation of a strip for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject by detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis subject, preferably wherein the strip has a cutoff value of 500 pg/mL for H-NGAL.
Use of a combination of a molecule that specifically binds to H-NGAL protein and a molecule that specifically binds to interleukin-6 (IL-6) protein in the preparation of a strip for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject by detecting H-NGAL protein and IL-6 protein in peritoneal dialysis effluent of the peritoneal dialysis subject, wherein the strip preferably a cutoff value of 500 pg/mL for H-NGAL and a cut-off value of 200 pg/mL for IL-6.
A method for diagnosing, preferably quick diagnosing peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising: detecting H-NGAL protein in peritoneal dialysis effluent of the subject, if H-NGAL protein is greater than or equal to a cutoff value, indicating that the subject has peritonitis or is at a risk of peritonitis;

optionally, the method further comprises detecting IL-6 protein in the peritoneal dialysis effluent, if IL-6 protein is greater than or equal to a cutoff value, indicating that the subject has peritonitis or is at a risk of peritonitis.
The method of claim 9, wherein detecting H-NGAL comprises:

(a) detecting H-NGAL protein in the peritoneal dialysis effluent; or

(B) detecting total NGALs in the peritoneal dialysis effluent, including monomer NGAL, H-NGAL and heterodimer forms, and detecting the monomer and heterodimer forms, so as to determine the amount of H-NGAL.
The method of claim 9 or 10, wherein the cutoff value for H-NGAL is 500 pg/mL and optionally, the cut-off value for IL-6 is 200 pg/mL.
The method of any one of claims 9-11, comprising:

- obtaining a peritoneal dialysis effluent sample;

- contacting a first molecule, such as an antibody, that specifically binds to H-NGAL protein with the sample, optionally the first molecule is immobilized on a solid support; and

- detecting the formed complex.
The method of any one of claims 9-12, comprising:

- obtaining a peritoneal dialysis effluent sample;

- contacting a first molecule, such as an antibody, that specifically binds to H-NGAL protein with the sample, optionally the first molecule is immobilized on a solid support;

- adding a second molecule, such as an antibody, that specifically binds to H-NGAL protein, optionally labeled, wherein the second molecule and the first molecule bind to different epitopes on H-NGAL protein;

- optionally, adding a substance that specifically binds to the second molecule, such as an antibody against the second molecule, optionally labeled, and

- detecting the formed complex.
The method of any one of claims 9-13, comprising:

- obtaining a peritoneal dialysis effluent sample;

- contacting a first antibody molecule that specifically binds to H-NGAL protein with the sample, wherein the first antibody molecule is labeled with biotin;

- adding a second antibody molecule that specifically binds to H-NGAL protein, wherein the second antibody molecule is labeled with colloidal gold, and the second antibody molecule and the first antibody molecule are different antibodies binding to different epitopes on H-NGAL protein;

- adding streptavidin, optionally, wherein the streptavidin is immobilized on a solid support, and

- detecting the formed complex.
A method of treating peritonitis in a peritoneal dialysis subject, comprising:

(a) detecting H-NGAL protein in a peritoneal dialysis effluent of the subject;

(b) determining a level of H-NGAL;

(c) comparing the level of H-NGAL against a cutoff value; and

(d) administering an antibiotic therapy if the level of H-NGAL exceeds the cutoff value.
The method of claim 15, wherein the cutoff value for H-MGAL is 500 pg/mL.
The method of claim 15 or 16, wherein the antibiotic therapy is selected from the group consisting of ertapenem, cefoxitin, doripenem, imipenem, cilastatin, meropenem, moxifloxacin, piperacillin, tazobactam, ticarcillin, clavulanate and tigecycline; or cefepime, cefotaxime, ceftazidime or ceftriaxone, together with metronidazole; or cefazolin, cefotaxime, ceftriaxone, ciprofloxacin, levofloxacin, together with metronidazole; or cefepime, ceftazidime, ciprofloxacin, levofloxacin, together with metronidazole; or gentamicin or tobramycin together with clindamycin or metronidazole.
A strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a conjugate pad, a nitrocellulose membrane and optionally an absorbent pad, wherein the nitrocellulose membrane comprises a test line and a control line, wherein:

the conjugate pad comprises a first molecule, optionally labeled, that specifically binds to H-NGAL protein and optionally a second molecule, optionally labeled, that specifically binds to H-NGAL protein, optionally wherein the first molecule and the second molecule are different;

the test line comprises an immobilized substance that detects a complex formed by H-NGAL protein and the first molecule and/or the second molecule; and

the control line comprises an immobilized substance that specifically binds to the first molecule and/or the second molecule.
The strip of claim 18, wherein:

the conjugate pad further comprises a third molecule, optionally labeled, that specifically binds to IL-6 protein and optionally a fourth molecule, optionally labeled, that specifically binds to IL-6 protein, optionally wherein the third molecule and the fourth molecule are different;

the nitrocellulose membrane further comprises a test line comprising an immobilized substance that detects a complex formed by IL-6 protein and the third molecule and/or the fourth molecule, and

optionally, the control line comprises an immobilized substance that specifically binds to the third molecule and/or the fourth molecule.
A strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a conjugate pad, a nitrocellulose membrane and optionally an absorbent pad, wherein the nitrocellulose membrane comprises a test line and a control line, wherein:

the conjugate pad comprises:

(a) a first molecule that specifically binds to H-NGAL protein, optionally labeled, and optionally a second molecule that specifically binds to H-NGAL protein, optionally labeled, optionally wherein the first molecule and the second molecule are different;

(b) a third molecule that specifically binds to IL-6 protein, optionally labeled, and optionally a fourth molecule that specifically binds to IL-6 protein, optionally labeled, optionally wherein the third molecule and the fourth molecule are different;

the test line comprises a test line comprising an immobilized substance that detects a complex formed by H-NGAL protein and the first molecule and/or the second molecule, and a test line comprising an immobilized substance that detects a complex formed by IL-6 protein and the third molecule and/or the fourth molecule; and

the control line comprises an immobilized substance that specifically binds to the first molecule, the second molecule, the third molecule, and/or the fourth molecule.
The strip of any one of claims 18-20, wherein the molecule is labeled with a label selected from the group consisting of biotin, a fluorescence, a radioactivity, a luminescence, a chemistry, an enzyme and a particulate label preferably a colloidal gold label.
A strip for diagnosis, especially quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a solid support having a first end and a second end, and from the first end continuously comprising a sample pad, a biotinylated pad, a gold-labeled pad, a nitrocellulose membrane and an absorbent pad, wherein the nitrocellulose membrane comprises a test line and a control line, wherein:

the biotinylated pad comprises a biotin-labeled first molecule that specifically binds to H-NGAL protein;

the gold-labeled pad comprises a colloidal gold-labeled second molecule that specifically binds to H-NGAL protein;

the test line comprises immobilized streptavidin; and

the control line comprises an immobilized substance that specifically binds to the first molecule and/or the second molecule, optionally wherein the first molecule and the second molecule are different.
The strip according to any one of claims 18-22, wherein the molecule and/or the substance is selected from the group consisting of an antibody or an antigen-binding fragment thereof, a ligand and an aptamer, preferably from the group consisting of a polyclonal antibody, a monoclonal antibody, a humanized antibody, a human antibody, a chimeric antibody and an antigen-binding fragment thereof, more preferably is a monoclonal antibody or an antigen-binding fragment thereof.
The strip of any one of claims 18-23, wherein the molecule is a primary antibody or an antigen-binding fragment thereof, and the control line comprises a secondary antibody or an antigen-binding fragment thereof that binds to the first, second, third and/or fourth antibody, such as an anti-IgG antibody molecule.
The strip of any one of claims 18-24, which has at least one of the following characteristics:

(a) the sample pad overlaps with the conjugate pad, wherein the sample pad is above the conjugate pad;

(b) the conjugate pad overlaps with the nitrocellulose membrane, wherein the conjugate pad is above the nitrocellulose membrane;

(c) the biotinylated pad overlaps with the gold-labeled pad, wherein the biotinylated pad is above the gold-labeled pad;

(d) the gold-labeled pad overlaps with the nitrocellulose membrane, where the gold-labeled pad is above the nitrocellulose membrane; and

(e) the absorbent pad overlaps with the nitrocellulose membrane, wherein the absorbent pad is above the nitrocellulose membrane.
The strip of any one of claims 18-25, which has a cut-off value of 500 pg/mL for H-NGAL protein, and/or a cut-off value of 200 pg/mL for IL-6 protein.
A kit for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis patient, comprising a means for detecting H-NGAL protein, and optionally a means for detecting IL-6 protein, and optionally a reference colorimetric card, wherein a test result is determined to be negative or positive by comparing the test result to the reference colorimetric card.
The kit of claim 27, comprising the strip of any one of claims 18-26.
A device for diagnosis, preferably quick diagnosis of peritonitis or a risk of peritonitis in a peritoneal dialysis subject, comprising a part for detecting H-NGAL protein in peritoneal dialysis effluent of the peritoneal dialysis subject and optionally a part for detecting IL-6 protein, and optionally a part for displaying test results.
The device of claim 29, comprising a part indicating that the subject has or is at a risk of peritonitis if H-NGAL protein in the peritoneal dialysis effluent is greater than or equal to a cutoff value such as 500 pg/mL, and optionally if IL-6 protein in the peritoneal dialysis effluent is greater than or equal to a cutoff value such as 200 pg/mL.
The strip of any one of claims 18-26, the kit of claim 27 or 28 and/or the device of claim 29 or 30, for use in the method of any one of claims 9-17.