Diagnostic Test with Lateral Flow Test Strip

Abstract

A diagnostic test apparatus comprises: an elongate housing defining a test strip holder containing a lateral flow test strip; a fluid sampling chamber provided with an opening connecting the fluid sampling chamber with the test strip holder; a viewing window in the elongate housing allowing reading of one or more portions of the lateral flow test strip; and a connector configured to couple the diagnostic test apparatus to a bulk source of fluid.

The apparatus may be included in a kit of parts. The apparatus is useful for detecting peritonitis. The bulk source of fluid may be peritoneal dialysate. Various markers may be determined in the bulk source of fluid such as MMP8, IL-6, HNE, MMP2, MMP9, TIMP1, TIMP2, NGAL, A1AT, desmosine, fibrinogen, IL-8, calprotectin, fMLP, IL1b, cystatin C, HSA, RBP4, SPD, MPO, sICAM and TNFa. Detection of the markers to indicate peritonitis may also inform treatment choices.

Claims

1.-32. (canceled)

33. A method of detecting peritonitis in a subject, selecting a subject for treatment with an antibiotic or predicting responsiveness of a subject to treatment with an antibiotic, the method comprising determining the level of at least one marker selected from MMP8, IL-6, HNE, MMP2, MMP9, TIMP1, TIMP2, NGAL, A1AT, desmosine, fibrinogen, IL-8, calprotectin, fMLP, IL1b, cystatin C, HSA, RBP4, SPD, MPO, sICAM and TNFa in a sample of peritoneal dialysate wherein: (i) an increased level of at least one of MMP8, IL-6, HNE, MMP2, MMP9, TIMP1, TIMP2, NGAL, A1AT, desmosine, IL-8, calprotectin, fMLP, IL1b, cystatin C, HSA, RBP4, SPD, MPO, sICAM and TNFa and/or a decreased level of fibrinogen is indicative of peritonitis; (ii) an increased level of at least one of MMP8, IL-6, HNE, MMP2, MMP9, TIMP1, TIMP2, NGAL, A1AT, desmosine, IL-8, calprotectin, fMLP, IL1b, cystatin C, HSA, RBP4, SPD, MPO, sICAM and TNFa and/or a decreased level of fibrinogen results in selection of the subject for treatment with an antibiotic; or (iii) an increased level of at least one of MMP8, HNE, MMP2, MMP9, TIMP1, TIMP2, NGAL, A1AT, desmosine, IL-6, IL-8, calprotectin, fMLP, IL1b, cystatin C, HSA, RBP4, SPD, MPO, sICAM and TNFa and/or a decreased level of fibrinogen predicts responsiveness of the subject to treatment with an antibiotic.

34. The method of claim 33, wherein the at least one marker is selected from MMP8, HNE, MMP2, MMP9, IL-6, calprotectin and MPO.

35. A method of treating peritonitis comprising administering an antibiotic to the subject suffering from peritonitis, wherein the subject has been selected for treatment by performing the method of claim 33.

36. A method of treating peritonitis comprising administering an antibiotic to the subject suffering from peritonitis, wherein the subject displays, in a sample of peritoneal dialysate, an increased level of at least one of MMP8, IL-6, HNE, MMP2, MMP9, TIMP1, TIMP2, NGAL, A1AT, desmosine, IL-8, calprotectin, fMLP, IL1b, cystatin C, HSA, RBP4, SPD, MPO, sICAM and TNFa and/or a decreased level of fibrinogen.

37. The method of treating peritonitis of claim 35, wherein the subject displays an increased level of at least one of MMP8, HNE, MMP2, MMP9, IL-6, calprotectin and MPO.

38. The method of treating peritonitis of claim 35, wherein the antibiotic is: a) selected from an aminoglycoside, a cephalosporin, a glycopeptide, a penicillin, a quinolone, aztreonam, clindamycin, imipenem-cilastin, linezolid, metronidazole, rifampin and an antifungal and/or b) administered intraperitoneally, orally or intravenously (preferably intraperitoneally); and/or c) administered during peritoneal dialysis and/or d) administered with the dialysis fluid utilised in the peritoneal dialysis and/or e) administered separately from the dialysis fluid utilised in the peritoneal dialysis.

39. A lateral flow testing device for detecting at least MMP8 and IL-6 in a sample, wherein the device comprises a lateral flow test strip comprising: (a) a sample receiving zone; (b) one or more test lines downstream of the sample receiving zone, the one or more test lines comprising immobilized or immobilizable first capture molecules which can specifically bind to MMP8 and immobilized or immobilizable second capture molecules which can specifically bind to IL-6; (c) first reporter molecules which can specifically bind to MMP-8 specifically bound by the first capture molecules; and (d) second reporter molecules which can specifically bind to IL-6 specifically bound by the second capture molecules; wherein, in use, the sample is transmitted from the sample application zone to the one or more test lines resulting in capture of MMP8 and IL-6 and reporter molecules thereby detecting the markers in the sample if present.

40. The lateral flow testing device of claim 39 further comprising a control zone, downstream of the one or more test lines in relation to the sample application zone, comprising immobilized or immobilizable further capture molecules which bind to the reporter molecules or to a control molecule to indicate successful completion of an assay using the device.

41. The lateral flow testing device of claim 39, wherein the reporter molecules are labelled, either directly or indirectly.

42. The lateral flow testing device of claim 39, wherein the capture molecules and/or the reporter molecules are antibodies, or fragments or derivatives thereof.

43. A diagnostic test apparatus comprising: an elongate housing defining a test strip holder containing a lateral flow test strip; a fluid sampling chamber provided with an opening connecting the fluid sampling chamber with the test strip holder; a viewing window in the elongate housing allowing reading of one or more portions of the lateral flow test strip; and a connector configured to couple the diagnostic test apparatus to a bulk source of fluid.

44. A diagnostic test apparatus as claimed in claim 43, wherein the connector: a) is configured to establish fluid communication between the bulk source of fluid and the fluid sampling chamber and/or b) comprises an interference fit connector and/or c) comprises a tubular element.

45. A diagnostic test apparatus as claimed in claim 44, wherein the tubular element: i) contains the fluid sampling chamber and/or ii) comprises a first end and a second end and the fluid sampling chamber is interposed between the first end and the second end.

46. A diagnostic test apparatus as claimed in claim 45, wherein the first end is open and the second end is closed to thereby enable a volume of fluid to pass into, and be retained within, the fluid sampling chamber during testing.

47. A diagnostic test apparatus as claimed in claim 44, wherein the tubular element is configured for push-fit coupling to a tube of the bulk source of fluid.

48. A diagnostic test apparatus as claimed in claim 47, wherein the tubular element comprises an O-ring seal for engaging the tube of the bulk source of fluid.

49. A diagnostic test apparatus as claimed in claim 43, wherein the connector is integral with the elongate housing.

50. A diagnostic test apparatus as claimed in claim 43, further comprising a puncturing element for opening fluid communication between the bulk source of fluid and the fluid sampling chamber.

51. A kit of parts comprising: a diagnostic test apparatus as claimed in claim 43; and a bulk source of fluid.

52. A method of carrying out a diagnostic test on a bulk source of fluid using a diagnostic test apparatus of the type comprising: an elongate housing defining a test strip holder containing a lateral flow test strip, a fluid sampling chamber provided with an opening connecting the fluid sampling chamber with the test strip holder, and a viewing window in the elongate housing allowing reading of one or more portions of the lateral flow test strip; the method comprising the steps of: coupling the diagnostic test apparatus to the bulk source of fluid by use of a connector; during or after coupling of the connector, establishing a fluid communication between the bulk source of fluid and the fluid sampling chamber of the diagnostic test apparatus to convey fluid from the bulk source of fluid into the fluid sampling chamber; causing fluid to pass from the fluid sampling chamber through the opening to wet the lateral flow test strip.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0195] The present disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0196] FIG. 1: A schematic representation of peritoneal dialysis;

[0197] FIGS. 2 to 5: A first embodiment of diagnostic test apparatus according to the present disclosure;

[0198] FIGS. 6 to 9: A second embodiment of diagnostic test apparatus according to the present disclosure;

[0199] FIGS. 10 to 13: A third embodiment of diagnostic test apparatus according to the present disclosure;

[0200] FIGS. 14 to 19: A fourth embodiment of diagnostic test apparatus according to the present disclosure;

[0201] FIG. 20A: Scatter graph showing median and interquartile range (IQR) generated from ELISA data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0202] FIG. 20B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown;

[0203] FIG. 21A: Scatter graph showing median and IQR generated from LF data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0204] FIG. 21B: ROC curve for the diagnosis of infection;

[0205] FIG. 22: Decision tree analysis providing initial cut-off for levels of MMP8;

[0206] FIG. 23A: Scatter graph showing median and IQR generated from zymography data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0207] FIG. 23B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown;

[0208] FIG. 24A: Scatter graph showing median and IQR generated from MMP9 data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0209] FIG. 24B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown;

[0210] FIG. 25A: Scatter graph showing median and IQR generated from HNE data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0211] FIG. 25B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown;

[0212] FIG. 26A: Scatter graph showing median and IQR generated from IL6 data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0213] FIG. 26B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown;

[0214] FIG. 27A: Scatter graph showing median and IQR generated from IL8 data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0215] FIG. 27B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown;

[0216] FIG. 28A: Scatter graph showing median and IQR generated from calprotectin data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001);

[0217] FIG. 28B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown;

[0218] FIG. 29A: Scatter graph showing median and IQR generated from MPO data comparing peritonitis vs stable individuals (Mann-Whitney test p<0.0001); and

[0219] FIG. 29B: Receiver Operator Characteristic (ROC) curves for the diagnosis of infection, area under the curve (AUC) values are shown.

DETAILED DESCRIPTION

[0220] In the following the present disclosure will be described by way of example only for the testing of dialysate fluid for peritonitis infection where the dialysate fluid is contained in or flowing into a dialysate bag. It will be readily appreciated that the diagnostic test apparatus, kit of parts and methods herein may be utilised with other fluids and other containers and for testing for different substances and conditions.

[0221] A first embodiment of a diagnostic test apparatus 10 according to the present disclosure is shown in FIGS. 2 to 5 and comprises an elongate housing 11 defining a test strip holder 12 which contains a lateral flow test strip 13. A fluid sampling chamber 14 is provided that connects with the test strip holder 12 via an internal fluid opening. The elongate housing 11 is provided with a viewing window 16 allowing viewing and reading of a portion of the lateral flow test strip 13.

[0222] The lateral flow test strip 13 may project into the fluid sampling chamber 14 through the opening. Alternatively, a wick element may be provided for wicking fluid from the fluid sampling chamber through the opening into contact with the lateral flow test strip 13.

[0223] A connector 17 is provided for coupling the diagnostic test apparatus 10 to a bulk source of fluid. The connector 17 may be located at one end of the elongate housing 11 and may be formed integrally, or partly integrally therewith.

[0224] The connector 17 may comprise a tubular element 18 having an open first end 19 and an open second end 20. The fluid sampling chamber 14 may be located interposed between the first end 19 and the second end 20. As shown, the second end 20 may be coupled to a drain line 7 leading to a dialysate fluid bag. The first end 19 may be coupled to another drain line (not shown) for feeding fluid from a patient's abdomen via a catheter.

[0225] The connector 17 may comprise more than one piece. As shown, either or both of the first end 19 and second end 20 may comprise a separate tubular interconnector 27 allowing an interference push-fit coupling of the tubular element 18 with the drain lines. Alternatively, the size and shape of the first end 19 and second end 20 may be configured to directly receive the drain lines as an interference push-fit.

[0226] In use, fluid to be testedfor example fluid received from a drain line connected to a catheterpasses through the diagnostic test apparatus 10 as a stream of fluid passing from a first drain line fluidly coupled to the first end 19 of the connector 17 via the fluid sampling chamber 14 and out of the second end 20 of the connector 17 into the fluidly coupled drain line 7. The fluid flowing through the fluid sampling chamber wets the lateral flow test strip 13 either directly or via wetting of the intermediate wick element.

[0227] A second embodiment of a diagnostic test apparatus 10 according to the present disclosure is shown in FIGS. 6 to 9. Like reference numerals have been used for like components between embodiments. As with the first embodiment, the diagnostic test apparatus 10 comprises an elongate housing 11 defining a test strip holder 12 which contains the lateral flow test strip 13 and is provided with a viewing window 16 allowing viewing and reading of a portion of the lateral flow test strip 13.

[0228] As above, a connector 17 is provided for coupling the diagnostic test apparatus 10 to a bulk source of fluid. In this example the bulk source of fluid is shown as a dialysate fluid bag 3. The dialysate fluid bag 3 may comprise a flexible sac 61 having one or more tubes 63 extending therefrom. The connector 17 may be configured for coupling to an end of one of the tubes 63.

[0229] The connector 17 may be located at one end of the elongate housing 11 and may be formed integrally, or partly integrally therewith. The connector 17 may comprise a tubular element 18 as above having an open first end 19. However, in this embodiment the second end 20 of the tubular element 18 is closed. As most clearly seen in FIG. 9, the fluid sampling chamber 14 is interposed between the open first end 19 and the closed second end 20. FIG. 9 also illustrates the opening 15 which may be internal and which connects the fluid sampling chamber 14 with the test strip holder 12. The lateral flow test strip 13 may project into the fluid sampling chamber 14 through the opening 15. Alternatively, a wick element 23 may be provided for wicking fluid from the fluid sampling chamber 14 through the opening 15 into contact with the lateral flow test strip 13.

[0230] The connector 17 also contains a puncturing element 50 for establishing fluid communication with the dialysate fluid bag 3. In the example shown the puncturing element 50 comprises a piercing tube 52, which may be hollow and may be statically-mounted within the fluid sampling chamber 14. An O-ring seal 21 may be provided at the open first end 19.

[0231] The fluid sampling chamber 14 may contain a foam element 26. The foam element 26 may be a foam ring that surrounds the piercing tube 52. The foam element 26 may assist in transferring fluid from the fluid sampling chamber 14 to the wick element 23. Alternatively, the foam element 26 may act itself as the wick element and be in direct contact with the lateral flow test strip 13.

[0232] As shown, the first end 19 may be coupled to an end of a tube 63 of the dialysate fluid bag 3. Typically the tube 63 will be initially closed off to prevent leakage of fluid by means of a bung. In order to couple the connector 17 to the dialysate fluid bag 3, the end of the tube 63 is pushed into the open first 19 of the connector 17 causing puncturing of the bung by the piercing tube 52. In this way fluid communication between the dialysate fluid bag 3 and the fluid sampling chamber 14 is established allowing fluid to flow into the fluid sampling chamber 14 to wet the lateral flow test strip 13 either directly or via the wick element 23 and/or the foam element 26. The closed second end 20 of the tubular element 18 and the engagement of the O-ring seal 21 on the tube 63 prevents leakage of fluid outside the diagnostic test apparatus 10.

[0233] The foam element 26 may also absorb and retain a fluid sample within the diagnostic test apparatus 10. This may allow the diagnostic test apparatus 10 to be retained for later testing, re-testing or analysis of the fluid sample at a remote site. Suitable means may be provided, for example a push-fit cap, for closing off the open first end 19 of the tubular element 18 after the initial test to assist in retaining the fluid sample.

[0234] A third embodiment of a diagnostic test apparatus 10 according to the present disclosure is shown in FIGS. 10 to 13. Like reference numerals have been used for like components between embodiments. As with the previous embodiments, the diagnostic test apparatus 10 comprises an elongate housing 11 defining a test strip holder 12 which contains the lateral flow test strip 13 and is provided with a viewing window 16 allowing viewing and reading of a portion of the lateral flow test strip 13.

[0235] As above, a connector 17 is provided for coupling the diagnostic test apparatus 10 to a bulk source of fluid. In this example the bulk source of fluid is again shown as a dialysate fluid bag 3 having a flexible sac 61 with one or more tubes 63 extending therefrom. The tubes 63 may be closed off using bungs 64.

[0236] In this embodiment the connector 17 may be configured for coupling directly to the flexible sac 61, for example to a surface of the flexible sac 61.

[0237] The connector 17 may be located at one end of the elongate housing 11 and may be formed integrally, or partly integrally therewith. The connector 17 may comprise a tubular element 18 defining a fluid sampling chamber 14 therein. The connector 17 also contains a puncturing element 50 for establishing fluid communication with the dialysate fluid bag 3. In the example shown the puncturing element 50 comprises a hollow piercing pin 51 within the fluid sampling chamber 14. The hollow piercing pin 51 may be movably-mounted to be movable between a retracted position, as shown in FIG. 13, wherein the hollow piercing pin 51 is fully within the fluid sampling chamber and an extended position in which the hollow piercing pin 51 is driven outwards through an aperture provided in the otherwise closed second end 20 of the tubular element 18. The first end 19 of the tubular element 18 is provided with a plunger 54 which is operatively connected to the hollow piercing pin 51. The plunger 54 may be operated by pushing or twisting the plunger 54.

[0238] As above, the fluid sampling chamber 14 is interposed between the first end 19 and the second end 20 of the tubular element 18. As above, the lateral flow test strip 13 may project into the fluid sampling chamber 14 through the opening 15 or alternatively, a wick element 23 may be provided for wicking fluid from the fluid sampling chamber 14 through the opening 15 into contact with the lateral flow test strip 13.

[0239] The fluid sampling chamber 14 may contain a foam element 26. The foam element 26 may be a foam ring that surrounds the hollow piercing pin 51. The foam element 26 may assist in transferring fluid from the fluid sampling chamber 14 to the wick element 23. Alternatively, the foam element 26 may act itself as the wick element and be in direct contact with the lateral flow test strip 13.

[0240] As shown in FIG. 10, the second end 20 may be provided with an adhesive pad 30 for adhering the connector 17 to a wall of the flexible sac 61. A further seal element, for example an O-ring seal, may be provided on an underside of the adhesive pad 30.

[0241] After coupling of the connector 17 to the flexible sac 61, fluid communication between the dialysate fluid bag 3 and the fluid sampling chamber 14 may be established by operating the plunger 54 to drive the hollow piercing pin 51 into the extended position in which it is driven through and punctures the wall of the flexible sac 61 allowing fluid to flow into the fluid sampling chamber 14 via the foam element 26 and/or the wick element 23.

[0242] The foam element 26 may also absorb and retain a fluid sample within the diagnostic test apparatus 10. This may allow the diagnostic test apparatus 10 to be retained for later testing, re-testing or analysis of the fluid sample at a remote site. Suitable means may be provided, for example an adhesive seal, for closing off the aperture in the second end 20 of the tubular element 18 after the initial test to assist in retaining the fluid sample.

[0243] A fourth embodiment of a diagnostic test apparatus 10 according to the present disclosure is shown in FIGS. 14 to 19. Like reference numerals have been used for like components between embodiments. As with the previous embodiments, the diagnostic test apparatus 10 comprises an elongate housing 11 defining a test strip holder 12 which contains the lateral flow test strip 13 and is provided with a viewing window 16 allowing viewing and reading of a portion of the lateral flow test strip 13.

[0244] As above, a connector 17 is provided for coupling the diagnostic test apparatus 10 to a bulk source of fluid. In this example the bulk source of fluid is again shown in FIG. 14 as a dialysate fluid bag 3 having a flexible sac 61 with one or more tubes 63 extending therefrom. The tubes 63 may be closed off using bungs 64.

[0245] In this embodiment the connector 17 may be configured for coupling directly to one or both tubes 63 with a clipping action.

[0246] The diagnostic test apparatus 10 may comprise two clamping legs 70, 71 wherein one of the clamping legs may comprise the elongate housing 11. The two clamping legs 70, 71 may be moved between an open configuration as shown in FIG. 18 and a closed configuration as shown in FIG. 19. A retention clip 72 may be provided at the distal ends of the clamping legs 70, 71 which allows the diagnostic test apparatus 10 to be at least temporarily retained in the closed configuration without manual intervention.

[0247] The connector 17 may comprise a tubular element 18 formed by the interaction of the two clamping legs 70, 71. As shown in FIGS. 15 and 18, each clamping leg may be provided with a part-tubular recess 73, 74, optionally semi-tubular recesses, that when brought together in the closed configuration define a tubular cavity 80 therebetween. The tubular cavity 80 may be provided with a foam element 26 which may be in the form of two part-tubular foam pieces 76, 77 lining the two part-tubular recesses 73, 74. In the closed configuration the two part-tubular foam pieces 76, 77 may be brought into contact and alignment to provide a tubular foam element that lines the tubular cavity 80.

[0248] Optionally, each clamping leg 70, 71 may further be provided with an additional part-tubular recess 78, 79, optionally semi-tubular recesses, that when brought together in the closed configuration define an additional tubular cavity 81 therebetween.

[0249] The elongate housing 11 as shown in FIG. 17 comprises a fluid sampling chamber 14 that communicates with or is formed by the part-tubular foam piece 77 in the tubular cavity 80 and also the test strip holder 12 via an opening 15. As above, the lateral flow test strip 13 may extend directly through the opening 15 into contact with the foam element 26 in the form of the tubular foam element or a wick element 23 may be interposed.

[0250] The connector 17 also contains a puncturing element 50 for establishing fluid communication with the dialysate fluid bag 3. In the example shown the puncturing element 50 comprises a blade 53 which is movable into the tubular cavity 80 when the clamping legs 70, 71 are in the closed configuration. As shown in FIG. 18, the blade 53 may be mounted on a pivotable third leg 75 which may be pivotally connected to one of the clamping legs 70, 71. The blade 53 may be pivoted into the tubular cavity 80 of the tubular element 18 though an aperture provided in the one of the clamping legs 70, 71.

[0251] The diagnostic test apparatus 10 may be coupled to one or two tubes 63 of the dialysate fluid bag 3 as shown in FIG. 14 by clipping the tubes 63 into the tubular cavity 80 and additional tubular cavity 81.

[0252] After or during coupling of the connector 17 to the one or more tubes 63, fluid communication between the dialysate fluid bag 3 and the fluid sampling chamber 14 may be established by pivoting the third leg 75 to drive the blade 53 into the tubular cavity 80 wherein it is driven through and punctures the wall of the tube 63 allowing fluid to flow into the tubular cavity 80 where it soaks the tubular foam element. Fluid is then transferred via the tubular foam element onto the lateral flow test strip 13.

[0253] The blade 53 may be provided with a central aperture 55 which allows fluid to pass across the plane of the blade 53. This may allow, after puncturing of the tube 63, fluid to be drained from the dialysate fluid bag 3 why carrying out the test. In other words fluid may freely flow through the tubular cavity 80 to drain while wetting the foam element sufficiently to transfer fluid to the lateral flow test strip 13.

[0254] The foam element 26 may also absorb and retain a fluid sample within the diagnostic test apparatus 10. This may allow the diagnostic test apparatus 10 to be retained for later testing, re-testing or analysis of the fluid sample at a remote site. Suitable means may be provided, for example adhesive seals or caps, for closing off the tubular cavity 80 after the initial test to assist in retaining the fluid sample.

Example 1Pilot Data to Show Selection of Biomarkers

[0255] Waste PD fluid was collected from 91 patients with peritonitis and 30 stable patients and stored at 80 C. All samples were analysed for more than 50 potential biomarkers using a variety of reference assays (immunoassays, zymography and protease substrate assays).

[0256] Of the potential biomarkers analysed MMP8 was found to be significantly elevated in peritonitis patients compared to stable PD patients.

[0257] The median level of MMP8 levels in waste PD fluid was 0.032 ng/mL (IQR=0.0 ng/mL-0.076 ng/mL) compared to 23.09 ng/mL (IQR=10.62 ng/mL-37.91 ng/mL) in individuals suffering from peritonitis (FIG. 20A). This marker has excellent diagnostic accuracy with a ROC AUC of 0.9963 (positive predictive value=1.00, negative predictive value=0.97; FIG. 20B and table 2).

[0258] The ability of the assay to perform in a lateral flow format was investigated. For a subset of the samples (peritonitis n=26 and stable n=10) the LF devices produced equivalent results to the ELISA (Spearman's rank=0.808, p<0.001) with an ROC AUC of 1 and a p value of <0.001. Results are shown in FIGS. 21A and 21B.

MMP8 Decision Tree to determine cut-off values:

[0259] The preliminary study provided a cut-off value of 0.418 ng/mL using decision tree analysis (SPSS).

[0260] Results are shown in FIG. 22 and performance is summarised in Table 3 below:

TABLE-US-00002 Classification Predicted Observed Stable Peritonitis Percent Correct Stable 30 0 100.0% Peritonitis 1 89 98.9% Overall Percentage 25.8% 74.2% 99.2% Growing Method: CRT Dependent Variable: VAR00001

[0261] The performance of a selection of the biomarkers tested is summarised in Table 4 below:

[0262] While the above embodiments and examples have been described in the context of testing for infection of dialysate fluid, preferably contained in dialysate bags, the present disclosure is not so limited. As will be appreciated, the diagnostic test apparatus, kit of parts and methods may be applied for the testing of other bulk sources of fluid and for other purposes as set out in the appended claims.

[0263] The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and accompanying figures. Such modifications are intended to fall within the scope of the appended claims. Moreover, all aspects and embodiments of the invention described herein are considered to be broadly applicable and combinable with any and all other consistent embodiments, including those taken from other aspects of the invention (including in isolation) as appropriate. Various publications are cited herein, the disclosures of which are incorporated by reference in their entireties.