WO2021064679A1

WO2021064679A1 - Diagnostic method for the detection of pepsin in a sample of tear fluid

Info

Publication number: WO2021064679A1
Application number: PCT/IB2020/059276
Authority: WO
Inventors: Luigi Mercuri
Original assignee: Drugs Minerals And Generics Italia S.R.L. In Forma Abbreviata D.M.G. Italia S.R.L.
Priority date: 2019-10-02
Filing date: 2020-10-02
Publication date: 2021-04-08
Also published as: EP4038387A1

Abstract

The present invention relates to a diagnostic method for the detection of pepsin in a sample S of tear fluid, a diagnostic device used to implement said method, and the use of said diagnostic device for the detection of pepsin suspected to be contained in a sample of tear fluid.

Description

DIAGNOSTIC METHOD FOR THE DETECTION OF PEPSIN IN A SAMPLE OF TEAR FLUID

The present invention relates to a diagnostic method for the detection of pepsin in a sample S of tear fluid. Furthermore, the present invention relates to a diagnostic device used to implement said method. Furthermore, the present invention relates to a use of said diagnostic device for the detection of pepsin suspected to be contained in a sample of tear fluid. Gastroesophageal reflux disease (GERD) is a condition that develops when a reflux of stomach contents causes complications and/or problematic symptoms. Such disease manifests itself with symptoms such as pyrosis and/or regurgitation, and it may cause inflammatory lesions to the oesophagus (oesophagitis), or ulcers, or metaplastic transformation of the mucosa (Barrett's oesophagus). Furthermore, gastric reflux can cause inflammatory disorders even in extra-oesophageal regions, such as for example the upper respiratory tract, ocular region and/or ear canal, resulting in laryngopharyngeal reflux disease (in short, LPR) or extra-oesophageal reflux disease.

The methods currently used for diagnosis of GERD comprise questionnaires and PPI (proton pump inhibitor) tests, and endoscopy or oesophageal pFI-metry.

The PPI test is carried out by administering drugs that reduce the amount of acid in the stomach; it is believed that a patient who responds to proton pump inhibitors is likely to be suffering from GERD.

On the other hand, oesophageal pH-metry is an endoscopy examination which, by means of a probe, allows to observe the condition of the oesophagus and to carry out a direct physiological measurement of the acid therein, thus allowing to differentiate the physiological refluxes from refluxes of pathological significance. The main drawbacks of the diagnostic techniques currently used lie in the poor sensitivity and specificity of the PPI test in association with the questionnaires, and in the invasiveness of the endoscopy or oesophageal pFI-metry. The latter methodology also has the further limit of not being effective in determining “non-erosive GERD” (which does not corrode or affect the walls of the oesophagus), a prevalent type with respect to the “erosive" type in the population of patients with GERD. The presence of pepsin in saliva has been studied in the prior art with the aim of diagnosing subjects with potentially GERD-related disorders, using lateral flow devices using specific human monoclonal antibodies to capture and identify the pepsin protein (Xing Du et al., BMC Gastroenterology, 17, 2017; Elif Saritas Yuksel B et al., The Laringoscope, 122, 1312-1316, 2012). Furthermore, an article was published describing the use of the ELISA (enzyme-linked immunosorbent assay) method for the identification of pepsin in tear samples from children with suspected laryngopharyngeal reflux disease (lannella G. et al., Intern. J. of Pediatric Otorhinolaryngology, 79, 2312-2315, 2015). Thus, since the methodologies available today are not satisfactory from the point of view of reliability or specificity, invasiveness and/or cost-effectiveness, after a long and intense research and development activity, the Applicant developed a method and a device capable of providing an adequate response to the current limits, drawbacks and problems.

More precisely, the present invention aims to provide a method and a device capable of detecting pepsin contained in a sample of tear fluid, thus providing a highly specific, not very invasive and cost-effective indication of a disorder and/or a disease associated with gastric reflux, with symptoms in both the gastroesophageal region and in the extra-oesophageal region, as defined in the present invention.

As a matter of fact, since pepsin is one of the main enzymes with proteolytic function during digestion, traces of this enzyme have been found to have the ability to reach the precorneal tear film through the nasolacrimal duct, after reaching the nasopharynx with the reflux attacks.

Thus, the inventors of the present invention established that a detection of pepsin in the tear fluid of an individual represents a unique indicator of the presence of reflux, and that therefore there is a possibility that a subject has a disorder or a disease associated with the latter.

Thus, forming an object of the present invention is a diagnostic method for the detection of pepsin in a sample of tear fluid, having the features as defined in the attached claims.

Furthermore, forming an object of the present invention is a diagnostic device used to implement said method, having the features as defined in the attached claims.

Furthermore, forming an object of the present invention is a use of said diagnostic device for the detection of pepsin suspected to be contained in a sample of tear fluid, having the features as defined in the attached claims.

The present invention will be illustrated hereinafter based on the attached figures, provided solely by way of non-limiting example of the present invention, wherein:

- figure 1 shows a plan view of a diagnostic device, subject of the present invention, according to a possible embodiment;

- figures 2A, 2B, 2C schematise the components inside the device of figure 1, in perspective view and in various and subsequent steps of the present method.

DETAILED DESCRIPTION OF THE INVENTION

Forming an object of the present invention is a diagnostic method comprising the following steps:

(i) contacting a sample S of tear fluid suspected to contain pepsin P and a labelling substance M configured for specifically binding pepsin P;

(ii) formation of the bond between said labelling substance M and pepsin P possibly contained in the sample S, so as to obtain marked pepsin PM;

(iii) detection of said marked pepsin PM.

With regard to the terminology used in this description, the term "tear fluid” is used to indicate an amount of bodily fluid or liquid substance, secreted by the tear glands of the eye.

The detection preferably provides for a qualitative and/or quantitative determination of the presence of pepsin contained in the sample S, thanks to the labelling substance M which - as mentioned - binds pepsin specifically.

Preferably, prior to the contacting step (i), the tear fluid is sampled superficially to the eye of a subject, or in a surface region adjacent to the eye, for example, an amount of tear fluid flowing out from the palpebral fissure or at the cornea.

Said sampling of the tear fluid can be carried out according to methods and equipment known in the art. Preferably, the tear fluid could be made to flow or be absorbed (at the cornea, or at the epidermis around the eye) on an absorbent test strip comprising the labelling substance M.

For example, the absorbent test strip could comprise or, alternatively, consist of a strip of porous material (for example paper or polymer) in which there is incorporated, or on whose surface there is arranged, or absorbed, or adsorbed, the labelling substance M.

In the present description, the expression "to specifically bind pepsin” is used to indicate that the labelling substance M has features such to bind pepsin P, preferably through a chemical bond, through a chelation, or through a surface absorption or adsorption, in a selective manner.

Preferably, the labelling substance M comprises or, alternatively, consists of an optical marker. More preferably, such an optical marker is detectable in the visible spectrum, even more preferably with the naked eye.

Preferably, the labelling substance M comprises or, alternatively, consists of a labelled monoclonal antibody. As regards the labelling of such antibody, at least one inert substance (for example latex), optionally in spherical or micro-spherical form, is preferably bound to each antibody. More preferably, the inert substance could be stained, or in any case capable of creating a visual contrast, for example with respect to the environment surrounding it.

In this description, the expression "marked pepsin” is used to indicate the combination of labelling substance M and pepsin P, generated by the step for forming the bond (ii).

Preferably, steps (i) to (ii) or steps (i) to (iii) are carried out under ambient conditions, that is to say at a temperature from about 15°C to 25°C and at about atmospheric pressure (about 1 atmosphere).

Step (iii) preferably comprises an optical detection, more preferably in the visible spectrum, for example with the naked eye. Step (i) and step (ii) are preferably carried out in solution. By way of example, the sample S of tear fluid and the labelling substance M (for example a solution containing the latter) could be mixed in liquid phase. More preferably, step (i) and step (ii) are carried out on an absorbent test strip comprising the labelling substance M.

Preferably, the contacting step (i), preceding the step of forming a bond (ii), comprises the following steps: (i.a) providing a test strip 2 comprising one or more capillaries that extend along a main extension direction X of such strip 2, between a proximal region 4 to which the labelling substance M is releasably bound, and at least one distal region 6, 6';

(i.b) positioning the sample S of tear fluid at the proximal region 4.

By convention, the terms proximal and distal will be used in this description respectively with reference to the position of the sample S at the labelling substance M, and with the distancing pathway (“distaf) of the marked pepsin PM with respect to this position.

Preferably, the test strip 2 is at least partially made of a porous material 8 of the paper-like type, of micro- structured polymer and/or of a sintered polymer, delimiting said capillary or plurality of capillaries.

The porous material 8 of the test strip 2 is preferably coupled to a support material 10, for example to confer a structural rigidity to the porous material 8.

With regard to the releasable bond of the labelling substance M from the proximal region 4, in an embodiment such labelling substance M could be bound or immobilised to the proximal region 4 by means of a soluble binder, for example a water-soluble binder. By way of example, the soluble or water-soluble binder could be a solid salt-sugar matrix.

As a result, when the sample S of tear fluid comes into contact with the labelling substance M and with the soluble binder, the pepsin P possibly contained in the sample S will bind to the labelling substance M to obtain the labelling substance PM, while the liquid will partially dissolve the soluble or water-soluble binder thus releasing the labelling substance M, and then the marked pepsin PM, from its immobilisation to the proximal region 4.

Preferably, the detection range of the pepsin is comprised from 1 ng to 100 ng (for example, 10 ng, 20 ng, 30 ng, 40 ng, 50 ng, 60 ng, 70 ng, 80 ng, or 90 ng), preferably from 1 ng to 30 ng, advantageously from 5 ng to 22 ng, optionally comprised from 11 ng to 20 ng, of pepsin per millilitre of sample S of tear fluid. Preferably, such sample S could be diluted with a diluting agent, hence the detection ranges could be those indicated above even in the presence of a dilution/mixing of the tear fluid with the diluting agent. Preferably, the concentration (for example surface concentration) of labelling substance M in the proximal region 4 is such that the detection range is from 1 ng to 100 ng or from 1 ng to 30 ng, preferably from 5 ng to 22 ng, even more preferably from 11 ng to 20 ng.

Preferably, in the contacting step (i) or in the liquid sample positioning step (i.b), the sample S of tear fluid could be mixed with a diluting agent. By way of example, the by volume mixing ratio of the tear fluid with respect to the diluting agent could be from 3:1 to 1:3, advantageously from 2:1 to 1:2, for example of about 1 1

According to an embodiment, the diluting agent could comprise or, alternatively, consist of citric acid.

According to an embodiment, the detection step (iii), subsequently to step for the formation of the bond (ii), comprises the following steps:

(iii. a) releasing the marked pepsin PM from the proximal region 4;

(iii.b) through a capillary action of said strip 2, displacing the marked pepsin PM from the proximal region 4 to at least one distal region 6, 6' of said strip, to which a retaining substance T of the marked pepsin PM is anchored;

(iii.c) formation of a bond between said marked pepsin PM and said retaining substance T.

Preferably, the marked pepsin PM releasing step (iii. a) comprises a solubilisation of the soluble binder or the water-soluble binder.

As regards the displacement step (iii.2), the marked pepsin PM is displaced or moved by the tear fluid (and the optional diluting agent) - in the displacement direction Z shown by the arrows in figures 2A and 2B - up to the distal region 6, 6'. Anchored at the latter region is the retaining substance T which, in particular, is fixed to the distal region 6, 6' in a non-releasable manner (for example by means of an insoluble or non-water-insoluble binder).

As a result, when the marked pepsin PM and the tear fluid reach the distal region 6, 6', the marked pepsin PM will bind to the retaining substance T remaining blocked at the distal region 6, 6'. In this case, the tear fluid (and the optional diluting agent) will not release the product of step (iii. c) - that is, the marked pepsin PM bound to the retaining substance T - from the distal region 6, 6', due to the non-releasable connection of the retaining substance T with such region 6, 6'.

Nevertheless, the tear fluid (with the optional diluting agent) may possibly continue its process along the capillary or the plurality of capillaries up to an absorption region 12 (for example in the form of sponge or other absorbing material), arranged distally to the distal region 6, 6'.

Preferably, the retaining substance T is configured to specifically bind marked pepsin PM.

As regards the expression "to specifically bind marked pepsin”, in this description these terms are used to indicate that the retaining substance T has features such to bind marked pepsin PM, preferably through a chemical bond, through a chelation, or through a surface absorption or adsorption, in a selective manner. It should be observed that this expression does not exclude that the retaining substance T may also bind non-marked pepsin.

Preferably, the retaining substance T comprises or, alternatively consists of a monoclonal antibody. According to this variant, said monoclonal antibody is fixed to the distal region 6, 6' in a non-releasable manner.

Preferably, the distal region 6, 6' at least partially constitutes a region for detecting marked pepsin PM, for example a region for detecting marked pepsin PM with an optical marker substance M.

Preferably, the method discussed above is used as an aid for the diagnosis of a disorder or of a disease associated with gastric juice reflux (gastric reflux) of a subject. According to different embodiments, such disorder or disease is selected from the group consisting of: gastroesophageal reflux, oesophageal reflux, laryngopharyngeal reflux, extra-oesophageal reflux, irritation of the larynx, pyrosis, oesophagitis, oesophageal ulcer, or metaplastic transformation of the mucosa, tear dysfunction syndrome (TDS) or dry eye syndrome, conjunctivitis of the conjunctiva, conjunctivitis of the cornea, ocular inflammation and periocular inflammation.

In the context of the present invention, the terms "gastric juice reflux” and "gastric reflux” are synonyms and they are used interchangeably.

In the context of the present invention, the term "extra-oesophageal reflux” or "extra-oesophageal reflux disease” are synonyms and they define the diseases or disorders or symptoms in extra-oesophageal regions related to or deriving from the reflux of the gastric content or part thereof (for example pepsin) in said extra-oesophageal regions, such as for example, the upper respiratory tract (for example, larynx, pharynx, oral cavity, nasal passages), the ocular region (for example, eyeball and periocular region, comprising conjunctiva and tear duct) and/or the ear canal (for example, Eustachian tube, middle ear).

Furthermore, forming an object of the present invention is a diagnostic device 1 (in short, device of the invention) for implementing said diagnostic method of the invention. It should be observed that, even if this is not explained, this device 1 could comprise any preferred or accessory characteristic discussed in connection with the above method.

Preferably, such a device is a pocketable device. More preferably, said device 1 comprises or, alternatively, consists of a point-of-care test.

This device 1 preferably comprises or, alternatively, consists of a lateral flow test.

Preferably, the diagnostic device 1 comprises a test strip 2 comprising one or more capillaries that extend along a main extension direction X of said strip 2, between a proximal region 4 to which a labelling substance M configured to specifically bind pepsin P is releasably bound, and at least one distal region (6, 6') to which a retaining substance T of the marked pepsin PM with said marker substance M is anchored. By way of example, the illustrated variants show a pair of distal regions 6, 6', spaced from each other. In such variant, one of the two distal regions (for example the second distal region 6') could act as confirmation, or as control, of the correct execution of the diagnostic test.

With reference to the variant shown in figure 1, the diagnostic device 1 preferably comprises a casing 14 which delimits an internal compartment 16 which houses the test strip 2 (for example at least partially or fully).

Preferably, the casing 14 delimits an opening 18 for introducing the sample S into the internal compartment 16, at the proximal region 4.

The introduction opening 18 is preferably vertically superimposed on the proximal region 4 so that - under the conditions of use shown in figure 1 - the sample S of tear fluid can reach such region 4 by effect of the force of gravity.

Preferably, the casing 14 could delimit an inspection window 20 of the internal compartment 16, such to make the distal region 6, 6' detectable or observable from the outside.

Furthermore, forming an object of the present invention is a use of said diagnostic device of the invention for the detection of pepsin suspected to be contained in a sample of tear fluid.

According to an innovative aspect of the present invention, the present diagnostic method and diagnostic device of the invention provide a highly specific, minimally invasive and cost-effective indication of a disorder or of a disease associated with gastric reflux, as specified in the present invention.

Advantageously, the present method and device of the invention allow to carry out a diagnosis regarding the presence of pepsin in a simple and repeatable manner, and in the absence of electrically powered instrumentation.

Advantageously, the present method and device of the invention provide a detection immediately observable with the naked eye.

Advantageously, the present method and device of the invention allow to obtain a high selectivity and/or sensitivity in the detection of pepsin.

Advantageously, the present device of the invention allows to carry out a laboratory diagnosis, but also a home diagnosis, not only because of the extremely small overall dimensions.

With respect to the embodiments of the method of the invention, of the device of the invention and of the use of the aforementioned, a man skilled in the art may replace or modify the described characteristics according to the contingencies. These embodiments are also to be considered included in the scope of protection formalised in the following claims.

Furthermore, it should be observed that any embodiment may be implemented independently from the other embodiments described.

Embodiments (FRa_nr) of the present invention are reported hereinafter:

FRa1. A diagnostic method comprising the following steps:

(i) contacting a sample (S) of tear fluid suspected to contain pepsin (P) and a labelling substance (M) configured to specifically bind pepsin (P); (ii) binding said labelling substance (M) and the pepsin (P) possibly contained in the sample (S), so as to obtain marked pepsin (PM);

(iii) detection of said marked pepsin (PM).

FRa2. The method according to FRa1, wherein the step (i) comprises the following steps:

(i.a) providing a test strip (2) comprising one or more capillaries that extend along a main extension direction (X) of said strip (2), between a proximal region (4) to which the labelling substance (M) is releasably bound, and at least one distal region (6, 6');

(i.b) positioning the sample (S) of tear fluid at the proximal region (4).

FRa3. The method according to one of the preceding FRas, wherein, in step (i) or in step (i.b), the sample (S) of tear fluid is mixed with a diluting agent, for example citric acid, at a volume ratio ranging from 3:1 to 1 :3, advantageously from 2:1 to 1 :2, for example of about 1 :1.

FRa4. The method according to one of the preceding FRas, wherein the detection step (iii) comprises the following steps:

(iii. a) releasing the marked pepsin (PM) from the proximal region (4);

(iii.b) through a capillary action of said strip (2), displacing the marked pepsin (PM) from the proximal region (4) to the distal region (6, 6') of said strip (2), to which a retaining substance (T) of the marked pepsin (PM) is anchored;

(iii.c) bond between said marked pepsin (PM) and said retaining substance (T).

FRa5. The method according to FRa1, wherein step (i) and step (ii) are carried out in a solution, or on an absorbent test strip comprising the labelling substance (M).

FRa6. The method according to any one of the preceding FRas, wherein the labelling substance (M) comprises or, alternatively, consists of an optical marker, for example detectable in the visible spectrum. FRa7. The method according to one of the preceding FRas, wherein the labelling substance (M) comprises or, alternatively consists of a labelled monoclonal antibody, and/or wherein the retaining substance (T) comprises or, alternatively consists of a monoclonal antibody fixed to the distal region (6, 6') in a non-releasable manner.

FRa8. The method according to one of the preceding FRas, wherein the detection range of the pepsin (P) is from 1 ng to 30 ng, advantageously from 5 ng to 22 ng, optionally from 11 ng to 20 ng, of pepsin (P) per millilitre of sample (S) of tear fluid.

FRa9. The method according to any one of the preceding FRas, for the diagnosis of a disorder or of a disease associated with gastric juice reflux of a subject, preferably wherein said disorder or disease is selected from the group consisting of: gastroesophageal reflux, oesophageal reflux, laryngopharyngeal reflux, irritation of the larynx, pyrosis, esophagitis, oesophageal ulcers, and metaplastic transformation of the mucosa.

FRa10. A diagnostic device (1) for implementing the method according to any one of the preceding FRas, wherein said diagnostic device comprises a test strip (2) comprising one or more capillaries that extend along a main extension direction (X) of said strip (2), between a proximal region (4) to which a labelling substance (M) configured to specifically bind pepsin (P) is releasably bound, and a distal region (6, 6') to which a retaining substance (T) of the marked pepsin (PM) with said labelling substance (M) is anchored. FRa11. The diagnostic device according to the preceding FRas, wherein the test strip (2) is at least partially made of a porous paper material, a micro-structured polymer and/or a sintered polymer, delimiting said one or more capillaries.

FRa12. The diagnostic device according to any one of FRaslO -11, characterised in that it comprises or, alternatively, consists of a point-of-care test, preferably it comprises or, alternatively, consists of a lateral flow test.

FRa13. Use of a diagnostic device according to any one of FRaslO -12, for the detection of pepsin (P) suspected to be contained in a sample (S) of tear fluid.

Embodiments (Frb_nr) of the present invention are reported hereinafter:

FRb1. A diagnostic method comprising the following steps:

(i) contacting a sample (S) of tear fluid suspected to contain pepsin (P) and a labelling substance (M) configured to specifically bind pepsin (P);

(ii) binding said labelling substance (M) and the pepsin (P) possibly contained in the sample (S), so as to obtain marked pepsin (PM);

(iii) detection of said marked pepsin (PM), wherein step (i) comprises the following steps:

(i.b) positioning the sample (S) of tear fluid at the proximal region (4), and wherein the detection step (iii) comprises the following steps:

(iii. a) releasing the marked pepsin (PM) from the proximal region (4);

(iii.c) binding between said marked pepsin (PM) and said retaining substance (T), wherein the labelling substance (M) comprises or, alternatively, consists of an optical marker detectable in the visible spectrum.

FRb2. The method according to FRb1, wherein, in step (i) or in step (i.b), the sample (S) of tear fluid is mixed with a diluting agent, for example citric acid, at a volume ratio ranging from 3:1 to 1:3, advantageously from 2:1 to 1:2, for example of about 1:1.

FRb3. The method according to any one of the preceding FRbs, wherein the labelling substance (M) comprises or, alternatively consists of a labelled monoclonal antibody, and/or wherein the retaining substance (T) comprises or, alternatively consists of a monoclonal antibody fixed to the distal region (6, 6') in a non-releasable manner.

FRb4. The method according to any one of the preceding FRbs, wherein the detection range of the pepsin (P) is from 1 ng to 30 ng, advantageously from 5 ng to 22 ng, optionally from 11 ng to 20 ng, of pepsin (P) per millilitre of sample (S) of tear fluid.

FRb5. The method according to any one of the preceding FRbs, for the diagnosis of a disorder or of a disease associated with gastric juice reflux of a subject, preferably wherein said disorder or disease is selected from the group consisting of: gastroesophageal reflux, oesophageal reflux, laryngopharyngeal reflux, la irritation of the larynx, pyrosis, esophagitis, oesophageal ulcers, and metaplastic transformation of the mucosa.

FRb6. Use of a diagnostic device (1) for the detection of pepsin (P) suspected to be contained in a sample (S) of tear fluid by implementing the method according to any one of the preceding claims, wherein said diagnostic device (1) comprises a test strip (2) comprising one or more capillaries that extend along a main extension direction (X) of said strip (2), between a proximal region (4) to which a labelling substance (M) configured to specifically bind pepsin (P) is releasably bound, and a distal region (6, 6') to which a retaining substance (T) of the marked pepsin (PM) with said labelling substance (M) is anchored. FRb7. The use of the diagnostic device according to the preceding FRbs, wherein said test strip (2) is at least partially made of a porous paper material, a micro-structured polymer and/or a sintered polymer, delimiting said one or more capillaries.

FRb8. The use of the diagnostic device according to FRb7 or FRb8, wherein said device comprises or, alternatively, consists of a lateral flow test.

LIST OF REFERENCE NUMBERS

1 diagnostic device

2 test strip 4 proximal region

6, and/or 6' distal region 8 porous material 10 support material 12 discharge region 14 casing

16 inner compartment 18 introduction opening 20 inspection window M labelling substance P pepsin

PM marked pepsin S sample

T retaining substance X main extension direction Z displacement direction

Claims

1. A diagnostic method comprising the following steps:

(i.b) positioning the sample (S) of tear fluid at the proximal region (4), wherein the detection step (iii) comprises the following steps:

(iii. a) releasing the marked pepsin (PM) from the proximal region (4);

(iii.c) binding said marked pepsin (PM) and said retaining substance (T), and wherein the labelling substance (M) comprises or, alternatively, consists of an optical marker, for example detectable in the visible spectrum.

2. The method according to claim 1, wherein, in step (i) or in step (i.b), the sample (S) of tear fluid is mixed with a diluting agent, for example citric acid, at a volume ratio from 3:1 to 1:3, advantageously from 2:1 to 1 :2, for example of about 1:1.

3. The method according to any one of the preceding claims, wherein the labelling substance (M) comprises or, alternatively, consists of a labelled monoclonal antibody, and/or wherein the retaining substance (T) comprises or, alternatively, consists of a monoclonal antibody fixed to the distal region (6, 6') in a non-releasable manner.

4. The method according to any one of the preceding claims, wherein the detection range of the pepsin (P) is from 1 ng to 30 ng, advantageously from 5 ng to 22 ng, optionally from 11 ng to 20 ng, of pepsin (P) per millilitre of sample (S) of tear fluid.

5. The method according to any one of the preceding claims, for the diagnosis of a disorder or of a disease associated with gastric juice reflux of a subject, preferably wherein said disorder or disease is selected from the group consisting of: gastroesophageal reflux, oesophageal reflux, laryngopharyngeal reflux, irritation of the larynx, pyrosis, esophagitis, oesophageal ulcers, and metaplastic transformation of the mucosa.

6. Use of a diagnostic device (1), for the detection of pepsin (P) suspected to be contained in a sample (S) of tear fluid by implementing the method according to any one of the preceding claims, wherein said diagnostic device (1) comprises a test strip (2) comprising one or more capillaries that extend along a main extension direction (X) of said strip (2), between a proximal region (4) to which a labelling substance (M) configured to specifically bind pepsin (P) is releasably bound, and a distal region (6, 6') to which a retaining substance (T) of the marked pepsin (PM) with said labelling substance (M) is anchored.

7. The use of the diagnostic device according to the preceding claim, wherein said test strip (2) is at least partially made of a porous paper material, a micro-structured polymer and/or a sintered polymer, delimiting said one or more capillaries.

8. The use of the diagnostic device according to claim 7 or 8, wherein said device comprises or, alternatively, consists of a lateral flow test.