Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
  • A61M1/14—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
  • A61M1/28—Peritoneal dialysis ; Other peritoneal treatment, e.g. oxygenation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0205—Investigating particle size or size distribution by optical means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue
  • A61B5/14546—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue
  • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/41—Detecting, measuring or recording for evaluating the immune or lymphatic systems
  • A61B5/412—Detecting or monitoring sepsis
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/74—Details of notification to user or communication with user or patient; User input means
  • A61B5/746—Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/06—Investigating concentration of particle suspensions
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
  • G01N21/03—Cuvette constructions
  • G01N21/05—Flow-through cuvettes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/90—Investigating the presence of flaws or contamination in a container or its contents
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M2202/00—Special media to be introduced, removed or treated
  • A61M2202/04—Liquids
  • A61M2202/0413—Blood
  • A61M2202/0439—White blood cells; Leucocytes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M2205/00—General characteristics of the apparatus
  • A61M2205/33—Controlling, regulating or measuring
  • A61M2205/3306—Optical measuring means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/01—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials specially adapted for biological cells, e.g. blood cells
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/06—Investigating concentration of particle suspensions
  • G01N15/075—Investigating concentration of particle suspensions by optical means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/01—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials specially adapted for biological cells, e.g. blood cells
  • G01N2015/016—White blood cells
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
  • G01N21/03—Cuvette constructions
  • G01N21/05—Flow-through cuvettes
  • G01N2021/052—Tubular type; cavity type; multireflective
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N2021/4704—Angular selective
  • G01N2021/4711—Multiangle measurement
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N2021/4733—Discriminating different types of scatterers

Definitions

• a cell counter and diagnostic device A cell counter and diagnostic device
• the present invention relates to a cell counter and diagnostic device able to be used in a variety of situations, including accompanying treatments such as peritoneal dialysis and laboratory work, where determining the concentration of cells suspended in a medium or physiological liquid or solution is required.
• Peritoneal dialysis is a treatment used with human patients where the patient’s kidneys are no longer able to perform adequately. The treatment assists in filtering unwanted waste products from the patient’s blood. Peritoneal dialysis is used as an alternative to haemodialysis. In some instances, peritoneal dialysis is preferred since it can be performed without medical supervision and in the patient’s home. It may also find utility in assisting in the diagnosing of spontaneous bacterial peritonitis in patients with ascites
• FIG. 1 shows a schematic view of a typical peritoneal dialysis set up.
• the dialysis solution 10 is introduced into the patient's peritoneal cavity 40, via a port, whereby the patient’s peritoneal lining 30 acts to filter the patient’s blood.
• the waste effluent fluid 20 is collected for disposal.
• microbes in the peritoneal cavity can cause peritonitis, which can have life threatening consequences for the patient. It is not currently easy to monitor the levels of microbes (e.g. bacteria or fungi) in the peritoneal cavity and it is an aim of an embodiment of the present invention to address this issue and other issues not outlined here.
• microbes e.g. bacteria or fungi
• a device for determining a concentration of cells of a given size in a sample of fluid comprising a plurality of cells, comprising: a light source arranged to emit light along a central axis to illuminate the plurality of cells in the fluid sample; a detector arranged to receive light at a plurality of displacements from the central axis, the light having passed through the plurality of cells in the fluid sample, and to produce a plurality of signals, each associated with, and indicative of an intensity of the received light at, a respective one of the plurality of displacements; and a processor arranged to determine a concentration of cells of a given size, based on the plurality of signals from the detector, wherein the processor is arranged to compare the plurality of signals from the detector with one or more pre-stored thresholds or profiles, indicative of a particular concentration.
• the processor is arranged to: measure a first light intensity reading at a first displacement from the central axis and measure a second light intensity reading at a second displacement from the central axis and determine, using a first method, the concentration of cells on the basis of the first and second light intensity readings and a difference therebetween.
• the processor is arranged to determine the concentration of cells using a second method
• the first and second light intensity readings are taken at displacements proximal the central axis.
• the plurality of displacements are in the range of substantially 1° to 15°, measured from the central axis.
• the detector comprises a plurality of photodetectors, each associated with one of the plurality of displacements.
• the plurality of photodetectors are arranged on both sides of the central axis, such that a first subset of the plurality of displacements is positioned on a first side of the central axis and a second, non-overlapping, subset of the plurality of displacements is positioned on a second side of the central axis.
• the first method uses an Area Under the Curve, AUC, method and the second method uses a Generalised Weighted Ratio, GWR, method.
• the sample is contained within a container, wherein the container either contains a static sample or a dynamic, flowing, sample.
• the container is arranged such that light from the light source strikes it an angle sufficient to reduce reflection of light back to the light source.
• the device is arranged to provide user feedback in the form of one or more of a numerical concentration value or a warning that the concentration value exceeds a predefined threshold.
• the user feedback additionally comprises one or more of: an audible signal to the user; a visual signal to the user; and communicating with a remote device to transmit the concentration of cells to the remote device.
• a container for use with the device of the first aspect comprising an entry and an exit, defining respective ends of a flow path, whereby there is provided proximal the entry and the exit a kinked portion arranged to minimise light transmission into the container.
• the cuvette has a male connector at a first end and a female connector at a second end to couple to an effluent line.
• a container for use with the device of the first aspect wherein a pair of windows is provided permitting light to enter and exit the container, whereby the pair of windows are recessed from an outer surface such that contact from a user’s fingers is prevented or inhibited.
• an exterior of the surface of the container is opaque, except for the pair of windows.
• the container is keyed such that it may only be inserted in one orientation to the device of the first aspect.
• Figure 1 shows a peritoneal dialysis setup known in the prior art
• Figure 2 shows a schematic representation of an embodiment of the present invention
• Figure 3 shows a representation of light scattering which underlies embodiments of the invention
• Figures 4a-c show details of the arrangement of a cuvette or container, optical source and detectors according to an embodiment of the present invention
• Figure 5a shows a cuvette according to an embodiment of the present invention
• Figure 5b shows another cuvette according to an embodiment of the present invention
• Figure 6 shows a graph illustrating responses according to different concentrations of leukocytes in a sample.
• Figure 7 shows a schematic of certain functional parts of a device according to an embodiment of the invention.
• Embodiments of the present invention operate to detect the presence of cells in the effluent fluid 20 during peritoneal dialysis.
• the cells in question are typically leukocytes.
• a subset of leukocytes includes neutrophils. Neutrophils above a certain concentration are indicative of the patient fighting an infection. If left unchecked, such an infection can develop into a serious, potentially life threatening, occurrence of peritonitis.
• Early detection of infection by the indirect detection of a certain concentration of neutrophils, can be lifesaving. At the very least, it can provide an opportunity for the patient to be treated early, thereby avoiding possible hospital admission and the associated costs and risks of complication. If a bacterial infection is detected, then prompt treatment by a suitable antibiotic can be arranged.
• Figure 2 shows a representation of the mode of operation of a first embodiment of the present invention. This is not intended to represent the actual construction of the device and is to illustrate a mode of operation only.
• the device 100 is arranged to be attached to the effluent waste pipe 21 , such that effluent from the peritoneal dialysis process flows through the device 100. Effluent flows in at 131 and flows out at 132 into the effluent reservoir 20.
• entry port 131 and exit port 132 Interposed between entry port 131 and exit port 132 is a sample-receiving effluent reservoir, container or cuvette 120 which temporarily holds a sample of effluent fluid for analysis. In another embodiment, there is no flow of effluent and a static sample is analysed instead. All other operational details are the same.
• a flowing sample of effluent is analysed whilst flowing to the effluent reservoir 20 or other receptacle.
• the fluid flows through the analysis device en-route to the reservoir 20 and so the user is not required to dispose of any sample after analysis.
• the sample may be introduced into the cuvette or other suitable receptacle by means of a syringe or similar, whereby the sample is drawn off from or en-route to the effluent reservoir 20.
• the sample may be analysed and then disposed of.
• the second embodiment may be substantially similar to the first embodiment, except that there is no continuous flow of effluent 131 , 132.
• a different form of receptacle may be employed.
• One advantage of embodiments of the present invention is that in both the first and second embodiments, the sample for analysis is not required to undergo any preparatory treatment and so embodiments of the invention are well suited for use at home and/or by unskilled persons.
• the sample in the cuvette 120 is illuminated via a laser 110.
• the laser is a 5mW red laser having a wavelength in the region of 650-700nm.
• the LASER is provided in the form of a LASER diode.
• different embodiments may employ different powers and/or wavelengths, as required.
• a collimating system such as a lens, may also be required.
• Light from the laser or LED 110 passes through the cuvette 120, including the sample, and is detected by a detector 140 located at an opposite side of the cuvette 120.
• the detector 140 comprises one or more photodiodes which is/are sensitive to light at or about the wavelength transmitted by the laser or LED 110.
• the detector produces an electrical signal indicative of the strength of the received light.
• the electrical signal also provides position/angular information indicative of the angular displacement from a central axis 111. In this way, the intensity of light at one or more displacements can be analysed.
• the detector is arranged to be exposed to light scattered through the sample.
• One way to achieve this is to provide a detector in the form of an array of photodiodes, where the number of photodiodes gives a certain detection resolution.
• An alternative technique employs a CMOS array.
• the detector may be arranged to travel along a defined track, measuring light intensity at various points.
• the signal recorded at particular locations along the detector 140 gives a measure of the degree of scatter experienced by the light from source 110.
• the degree of scatter is indicative of the size and concentration of particles in the effluent.
• larger particles tend to result in a larger displacement from the axis 111 , and the intensity of light at a particular angle is indicative of the number of particles of a particular size.
• the particles of interest are leukocytes having a particular size. The number of such particles determined by measured light intensity at one or more given angular displacements may be compared to a defined threshold to indicate a potential issue for the user in question.
• FIG. 3 shows a further illustration of the principle involved, whereby light from source 110 illuminates sample cuvette 120, including effluent.
• sample is in the form of a continuous flow and, in the second embodiment, the sample is static.
• the mode of operation of both embodiments is identical.
• the light is scattered by the presence of the leukocytes in the sample and causes the light to be scattered, as shown.
• the degree of scattering is recorded by the detector 140. The degree and intensity of scattering correlates with the concentration of leukocytes in the sample, as described previously.
• the angle associated with a particular particle size depends on a number of factors including light intensity, the distance between the light source and the detector, path length through the cuvette amongst others. As such, the displacement angle associated with a particular particle size can vary depending upon the precise configuration employed.
• the angular displacement tends to fall in the range of 0 to 15° from the central axis 111.
• the range 0 to 12° is found to offer the best range, since readings at displacements above this range tend to be too small to be distinguishable.
• Figures 4a to 4c show details of a configuration of certain parts of the device according to an embodiment of the present invention.
• the optical source 110 is shown. It emits light towards and through cuvette 120, through a lens 112. The light thereby produced is scattered by the presence of leukocytes in the sample and so the light which leaves the cuvette is scattered somewhat. This scattered light is received at a detector 140.
• An individual photodetector is a photodiode 141 , with a plurality of these forming the overall detector 140. Since each photodetector 141 occupies a finite space, it is difficult to locate many such photodetectors 141 in the space available.
• a clinical diagnosis of peritonitis is associated with a concentration of 10 5 cells/ml.
• Embodiments of the present invention are able to detect a concentration of cells in the region of 10 4 cells/ml. While such a concentration may be present in a healthy user, the ability to detect changes in the range 10 4 to 10 5 cells/ml, offers an opportunity to provide an early warning of infection.
• Figure 5a shows a particular form of cuvette 200, which may be employed in place of cuvette 120 shown previously, for use in the first (dynamic) embodiment.
• the cuvette 200 is connected at one end to a male connector 220 and at a second end to a female connector 230.
• a flow path 201 is defined within the cuvette in which the effluent or other sample fluid runs.
• Each of the male and female connectors is attached to the effluent line so that effluent runs through the cuvette 200 and into the reservoir 20.
• the cuvette 200 is formed from an opaque plastics material, such that only light from laser or LED 110, which passes through window 210, enters the cuvette.
• first and second kinks or meanderings 202 are provided proximal each end of the flow path 201 in the cuvette. These have the effect of impeding stray light from the effluent line 21 from entering the cuvette 200 and possibly interfering with the analysis.
• the kinks 202 also have the effect of inhibiting the production of bubbles in the flow path which could otherwise interfere with the analysis.
• One surface of the cuvette 200 is transparent or less opaque and this is provided with an opaque sticker or seal 240 which is provided with a window or aperture 241 to facilitate the passage of light from laser or LED 110.
• the cuvette 200 is intended to be disposable and used once only.
• Figure 5b shows a cuvette 250 for use in the static system, where there is no flow of effluent through the cuvette.
• an effluent sample is introduced into the cuvette via cap 256 located at the top of the cuvette. This ensures that no sample can escape once introduced and the cap is closed.
• the cuvette 250 takes the form of a cartridge, for insertion into the diagnostic device.
• the majority of the cuvette is formed from an opaque plastics material so as to inhibit any stray light from entering the interior of the cuvette and to minimise any internal reflections.
• the first pair of windows 254 are located towards the top of the cuvette and are provided to permit a simple visual inspection to ensure that sample is present and to an appropriate level. They serve no operational role beyond this.
• the second pair of windows 252 are located towards the bottom of the cuvette and are arranged in the central optical axis whereby light from the source 110 passes through the rear and front windows 252 and then towards the detector.
• Figure 5b only one of the pair of windows is visible, but there is a corresponding window on the opposite face of the cuvette 250.
• This pair of windows 252 are provided in a slightly recessed position in the cuvette. The size of the recess is intended to prevent inadvertent touching of the windows by the user, since grease or other materials on the user’s fingers could adversely affect the operation of the device.
• the cuvette 250 is provided with a relatively flared front surface 260, whereby the outer diameter of this surface is greater than the outer diameter of the opposing surface. This allows the cuvette to be “keyed” such that it can only be inserted into the diagnostic device in a single orientation. This is since the inner container of the cuvette, which contains the sample does not necessarily have symmetrical optical properties and should be used in a single orientation only, hence the “keyed” arrangement.
• a label 258 which may comprise an identification symbol, such as a barcode or a QR code.
• Figure 6 shows a graph illustrating the effect of scattering of the light, from light source 110, through a sample in cases having different concentrations of leukocytes.
• the x-axis is a measure of the displacement (i.e. the angle of scatter, in degrees) from axis 111. In Figure 6, this runs from 0° to 12°.
• the y-axis records the intensity of the signal provided by detector 140 and so is a measure of the intensity of light at a particular displacement.
• a 5mW Laser having a wavelength in the region 650- 700nm.
• Different wavelengths and powers give different results, and the example given is only one of several options. The skilled person will realise that a different power will lead to different readings of light intensity and a different wavelength will lead to a different response.
• a wavelength in the range of 650-700nm is found to yield good results in detecting and determining a concentration of leukocytes. The curves shown represent five different concentrations of leukocytes: 5,000 cells/ml (300); 10,000 cells/ml (301); 25,000 cells/ml (302); 45,000 cells/ml (303); and 10,000,000 cells/ml (310).
• the profile of the respective curve follows a regular trajectory from a low concentration (300) to a higher concentration (303). However, when the concentration tends much higher, towards 10 7 cells/ml (310), the trajectory abruptly changes and the resultant profile ceases to resemble those corresponding to lower concentrations. Essentially, there comes a point where rather than present as a decaying curve (301-303), the curve has a much more linear profile where the gradient is substantially constant across the measured range.
• the curve profile changes.
• a threshold is determined which dictates which technique of the two is used. It has been found that once the second value (measured at 2°) is less than the first value (measured at 1°) by less than a 25% difference, then the GWR method should be used. If the difference is more than 25%, then the AUC method should be used.
• the absolute value of the threshold may differ, depending upon the particular setup of the apparatus and a threshold value between 10% and 40% may be appropriate with 25% being a preferred value in a particular case only.
• the threshold in terms of a percentage decrease per degree of displacement.
• the threshold may be considered as 25% per degree of displacement.
• intensity readings are taken at intervals of other than 1°, then the calculation may be adjusted accordingly.
• An alternative and in, some ways, complementary, technique examines the gradients at two locations on each curve and by means of a comparison therebetween, the correct technique is selected.
• an embodiment of the invention is arranged to examine a gradient at one end of the range and compare this with a gradient at another end of the range.
• the gradient at a first end of the range may be determined by examining the readings from the photodetectors arranged at 1° and 2°, determining a gradient from these two results, and then repeating the process with the readings from the photodetectors arranged at 11° and 12°.
• gradient is defined as the difference between two readings, divided the angular displacement between the same readings. The units of intensity are not relevant to this calculation, since a comparison of numerical values is all that is required,
• the first gradient is relatively steep and so indicative of a relatively lower concentration
• the second gradient is relatively flat, which acts to confirm this first approximation.
• the first gradient is relatively flat, as is the second one, and so the similarity between them is indicative of this much higher concentration.
• the device is arranged to calculate the concentration of cells using one of two different techniques. If the first gradient is different to the second gradient by more than a defined threshold, then an “area under the curve”, AUC, technique is used, whereas if the first and second gradients are substantially the same, within a further defined range, then a “Generalised Weighted Ratio”, GWR, technique is used. Calculating the AUC of the plot of scatter angle vs light intensity can be achieved using any convenient method such as the trapezoidal rule or other methods of integration. Within the appropriate range of cell concentrations, the cell concentration is proportional to the AUC and can be found by suitable calibration with known standards.
• the GWR method uses the light intensity recorded at 4 or more scatter angles/displacements and calculates a weighted average intensity.
• the weighting given to each angle can be found by a number of empirical and computational methods, such as regression analysis, based on measurements of known standards.
• the weighted average of the light intensities can then be used to calculate the cell concentration in unknown samples within the applicable range of concentrations.
• the comparison of gradients referred to above, which determines which method is to be used involves a switching point or threshold. For instance, if the first and second gradients do not differ by more than 25% then this is determined to be substantially the same for the purposes of determining the concentration and so the GWR method is used. However, if the first and second gradients differ by more than the same percentage, then this is determined to be substantially different and so the AUC method is used.
• the profile across all photodetectors is compared with one or more pre-stored profiles to better match the observed result with pre-calculated or premodelled concentration values.
• the device 100 may be provided with a display to indicate information to the user regarding the ongoing analysis. In a simple case, this could be in the form of an alert if the cell level is above a predefined threshold. More complex displays may return detailed results, although these may not be suitable or required in all cases.
• the device 100 may be provided with a form of communication interface whereby the user’s results are uploaded to a remote computer system, which may comprise the user’s personal records and/or a remote monitoring station whereby problematic results may be reviewed by a physician who may contact the patient in case of concern for theirwellbeing.
• a remote computer system which may comprise the user’s personal records and/or a remote monitoring station whereby problematic results may be reviewed by a physician who may contact the patient in case of concern for theirwellbeing.
• the communication interface may comprise a local wireless connection (such as Bluetooth) to a PC, which is then further connected via the internet to the remote computer system.
• a local wireless connection such as Bluetooth
• the device 100 may be able to communicate directly with the remote computer system via an integral cellular technology, for instance.
• Embodiments of the present invention provide many advantages over prior art solutions. For instance, use of the device requires no specialist knowledge on the part of the user, who is able to use it as an integral part of their dialysis set up.
• test is performed entirely in situ as part of the process it is monitoring. This means that there is no requirement to send samples to a lab for subsequent analysis.
• the options available to a user may be slightly different to those presented to a patient, since the laboratory worker will typically have a higher skill level in the use of the equipment and may require a different level of detail to a patient.
• the apparatus is arranged to measure a concentration of leukocytes in particular.
• the user may be interested in analysing other cell types. These may include, for instance, HL60 and Jurkat cells. Measurement of the concentration of these cell types may require an adjustment in the operation of the device, so that different result profiles will require a different processing to that applied to leukocytes. To facilitate this, an additional menu option may be provided so that the user is able to select the most appropriate processing to apply to the particular sample being analysed.
• FIG. 7 shows, for completeness, a schematic representation of certain functional parts of the device 100 according to an embodiment of the present invention.
• the device 100 is controlled by processor 400.
• Processor 400 is any suitable microprocessor or microcontroller, which is programmed to perform the operations required in order to perform the functions set out above.
• the program which causes the processor 400 to operate is stored in memory 420.
• the same memory 420 can provide working memory as well as data, such as pre-stored profiles and thresholds used in the analysis of a sample.
• the device 100 is operated via power supply 420.
• This may comprise an internal battery supply or an external mains-operated supply, as required.
• the processor 400 is arranged to drive the optical source 110 and to receive signals from the optical detector 140, as set out above.
• a result of the analysis is displayed on display 410.
• the same display may be configured to provide operational information, such as power status, as well as other warning or informational messages for a user.
• At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware.
• Terms such as ‘component’, ‘module’ or ‘unit’ used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality.
• FPGA Field Programmable Gate Array
• ASIC Application Specific Integrated Circuit
• the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors.
• These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables.
• components such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables.
• components such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables.

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