An NMR-based metabonomic approach to investigate the biochemical consequences of genetic strain differences: application to the C57BL10J and Alpk:ApfCD mouse

As the human genome sequencing projects near completion, there is an active search for technologies that can provide insights into the genetic basis for physiological variation and interpreting gene expression in terms of phenotype at the whole organism level in order to understand the pathophysiology of disease. We present a novel metabonomic approach to the investigation of genetic influences on metabolic balance and metabolite excretion patterns in two phenotypically normal mouse models (C57BL10J and Alpk:ApfCD). Chemometric techniques were applied to optimise recovery of biochemical information from complex (1)H NMR urine spectra and to determine metabolic biomarker differences between the two strains. Differences were observed in tricarboxylic acid cycle intermediates and methylamine pathway activity. We suggest here a new 'metabotype' concept, which will be of value in relating quantitative physiological and biochemical data to both phenotypic and genetic variation in animals and man.

A novel IL-18BP ELISA shows elevated serum IL-18BP in sepsis and extensive decrease of free IL-18

IL-18 binding protein (IL-18BP) is a circulating antagonist of the proinflammatory Th1 cytokine IL-18. It effectively blocks IL-18 by forming a 1:1 high affinity (Kd=400 pM) complex, exhibiting a very low dissociation rate. We have developed a sandwich ELISA for IL-18BPa and determined its limit of detection (62 pg/ml). Interference by IL-18 and related cytokines, as well as cross reactivity with other IL-18BP isoforms (b, c, and d) were determined. Using this ELISA, we measured serum IL-18BPa in large cohorts of healthy individuals and in septic patients. Serum IL-18BPa in healthy individuals was 2.15+/-0.15 ng/ml (range 0.5-7 ng/ml). In sepsis, the level rose to 21.9+/-1.44 ng/ml (range 4-132 ng/ml). Total IL-18 was measured in the same sera by an electrochemiluminescence assay and free IL-18 was calculated based on the mass action law. Total IL-18 was low in healthy individuals (64+/-17 pg/ml) and most of it ( approximately 85%) was in its free form. Total IL-18 and IL-18BPa were both elevated in sepsis patients upon admission (1.5+/-0.4 ng/ml and 28.6+/-4.5 ng/ml, respectively). At these levels, most of the IL-18 is bound to IL-18BPa, however the remaining free IL-18 is still higher than in healthy individuals. We conclude that IL-18BPa considerably inhibits circulating IL-18 in sepsis. Yet, exogenous administration of IL-18BPa may further reduce circulating IL-18 activity.

A comprehensive map of the human urinary proteome

The study of the human urinary proteome has the potential to offer significant insights into normal physiology as well as disease pathology. The information obtained from such studies could be applied to the diagnosis of various diseases. The high sensitivity, resolution, and mass accuracy of the latest generation of mass spectrometers provides an opportunity to accurately catalog the proteins present in human urine, including those present at low levels. To this end, we carried out a comprehensive analysis of human urinary proteome from healthy individuals using high-resolution Fourier transform mass spectrometry. Importantly, we used the Orbitrap for detecting ions in both MS (resolution 60 000) and MS/MS (resolution 15 000) modes. To increase the depth of our analysis, we characterized both unfractionated as well as lectin-enriched proteins in our experiments. In all, we identified 1,823 proteins with less than 1% false discovery rate, of which 671 proteins have not previously been reported as constituents of human urine. This data set should serve as a comprehensive reference list for future studies aimed at identification and characterization of urinary biomarkers for various diseases.

Immunodiagnosis of schistosomiasis by determination of the circulating antigens CAA and CCA, in particular in individuals with recent or light infections

In the present paper, we evaluate determination of circulating anodic (CAA) and cathodic (CCA) antigen for the diagnosis of an active Schistosoma infection in humans, in comparison to the diagnostic performance of parasitological examination and the demonstration of specific antibodies. Illustrated by three different studies, which all deal with the diagnosis of either recent or low intensity infections, we further discuss our experiences with these diagnostic methods. For the diagnosis of recent infections, specific antibody determination showed to be very sensitive, particularly in individuals originating from non-endemic areas. For the assessment of cure and for the diagnosis of active infections in endemic areas, the methods of choice are parasitological examination and CAA or CCA determination. Depending on infection levels of the target population and on logistic conditions, CAA and CCA determination may either replace parasitological examination or, in the case of light infections, may be used as a complementary diagnostic tool.

Evaluation of urine CCA assays for detection of Schistosoma mansoni infection in Western Kenya

Although accurate assessment of the prevalence of Schistosoma mansoni is important for the design and evaluation of control programs, the most widely used tools for diagnosis are limited by suboptimal sensitivity, slow turn-around-time, or inability to distinguish current from former infections. Recently, two tests that detect circulating cathodic antigen (CCA) in urine of patients with schistosomiasis became commercially available. As part of a larger study on schistosomiasis prevalence in young children, we evaluated the performance and diagnostic accuracy of these tests—the carbon test strip designed for use in the laboratory and the cassette format test intended for field use. In comparison to 6 Kato-Katz exams, the carbon and cassette CCA tests had sensitivities of 88.4% and 94.2% and specificities of 70.9% and 59.4%, respectively. However, because of the known limitations of the Kato-Katz assay, we also utilized latent class analysis (LCA) incorporating the CCA, Kato-Katz, and schistosome-specific antibody results to determine their sensitivities and specificities. The laboratory-based CCA test had a sensitivity of 91.7% and a specificity of 89.4% by LCA while the cassette test had a sensitivity of 96.3% and a specificity of 74.7%. The intensity of the reaction in both urine CCA tests reflected stool egg burden and their performance was not affected by the presence of soil transmitted helminth infections. Our results suggest that urine-based assays for CCA may be valuable in screening for S. mansoni infections.

Control efforts for schistosomiasis have in part been hampered by the lack of a sensitive and accurate test that can be utilized to rapidly map the prevalence of the disease in different areas. Recently, new tests have become commercially available that may address this problem. This study was designed to compare the new tests, which detect a schistosome antigen in patients' urine, with more traditional tests that look for parasite eggs in stool or anti-parasite antibodies in serum. We found that the new tests performed very well to detect schistosomiasis in children in western Kenya, an area with a high prevalence of Schistosoma mansoni infections. There was no apparent effect of soil transmitted helminth infections on the performance of the tests and the intensity of the antigen detection assays correlated well with the levels of S. mansoni eggs in the stool and schistosome-specific antibody in serum. Additional evaluation is needed in areas with lower schistosomiasis prevalence and intensity levels but we believe that point of contact testing of urine for schistosome antigen could be an effective tool in schistosomiasis mapping and control efforts.

The quantitative determination of glycosaminoglycans in urine with Alcian Blue 8GX

1. The effect of MgCl(2) concentration on the interaction of Alcian Blue 8GX and glycosaminoglycans in the urine of patients with mucopolysaccharidosis was studied by using a new quantitative micro method for the measurement of Alcian Blue-glycosaminoglycan complexes. This provided a means of measuring the critical electrolyte concentrations of urinary glycosaminoglycans. 2. Theoretical considerations based on the preceding paper (Whiteman, 1973) and experimental evidence provided here show that Alcian Blue 8GX may be used for the direct quantitative determination of total urinary glycosaminoglycans. The method is simple, requires sample volumes of 50mul or less, and gives results comparable with those obtained by other more complicated methods.

Use of circulating cathodic antigen (CCA) dipsticks for detection of intestinal and urinary schistosomiasis

An evaluation of a commercially available antigen capture dipstick that detects schistosome circulating cathodic antigen (CCA) in urine was conducted in representative endemic areas for intestinal and urinary schistosomiasis in Uganda and Zanzibar, respectively. Under field-based conditions, the sensitivity (SS) and specificity (SP) of the dipstick was 83 and 81% for detection of Schistosoma mansoni infections while positive predictive (PPV) and negative predictive values (NPV) were 84%. Light egg-positive infections were sometimes CCA-negative while CCA-positives included egg-negative children. A positive association between faecal egg output and intensity of CCA test band was observed. Estimating prevalence of intestinal schistosomiasis by school with dipsticks was highly correlated (r=0.95) with Kato-Katz stool examinations, typically within +/-8.5%. In Zanzibar, however, dipsticks totally failed to detect S. haematobium despite examining children with egg-patent schistosomiasis. This was also later corroborated by further surveys in Niger and Burkina Faso. Laboratory testing of dipsticks with aqueous adult worm lysates from several reference species showed correct functioning, however, dipsticks failed to detect CCA in urine from S. haematobium-infected hamsters. While CCA dipsticks are a good alternative, or complement, to stool microscopy for field diagnosis of intestinal schistosomiasis, they have no proven value for field diagnosis of urinary schistosomiasis. At approximately 2.6 US dollars per dipstick, they are presently too expensive to be cost-effective for wide scale use in disease mapping surveys unless Lot Quality Assurance Sampling (LQAS) strategies are developed.

Tamm-Horsfall urinary glycoprotein. The chemical composition

1. A revised amino acid and carbohydrate composition of human Tamm-Horsfall glycoprotein is presented. 2. No significant differences were obtained in the amino acid composition of Tamm-Horsfall glycoprotein isolated from patients with cystic fibrosis. 3. The glycoprotein was shown to possess a high half-cystine content of 1 per 11-12 amino acid residues, which has been confirmed by performic acid oxidation and S-alkylation with iodoacetate and iodoacetamide. No thiol groups were detected in the glycoprotein. 4. Treatment of the glycoprotein with 0.5m-sodium hydroxide at 4 degrees C for 2 days did not release heterosaccharide material, which suggests that the predominant carbohydrate-protein linkages present are not of the O-glycosidic type. 5. No N-terminal amino acid was detected in the glycoprotein.

Bladder cancer associated glycoprotein signatures revealed by urinary proteomic profiling

Current methods in the noninvasive detection and surveillance of bladder cancer via urine analysis include voided urine cytology (VUC) and some diagnostic urinary protein biomarkers; however, due to the poor sensitivity of VUC and high false-positive rates of currently available protein assays, detection of bladder cancer via urinalysis remains a challenge. In the study presented here, a rapid, high-sensitivity technique was developed to profile the N-linked glycoprotein component in naturally micturated human urine specimens. Concanavalin A (Con A) affinity chromatography coupled to nanoflow liquid chromatography was utilized to separate the complex peptide mixture prior to a linear ion trap MS analysis. Of 186 proteins identified with high confidence by multiple analyses, 40% were secreted proteins, 18% membrane proteins, and 14% extracellular proteins. In this study, the presence of several proteins appeared to be associated with the presence of bladder cancer, including alpha-1B-glycoprotein that was detected in all tumor-bearing patient samples but in none of the samples obtained from non-tumor-bearing individuals. The combination of Con A affinity chromatography and nano-LC/MS/MS provides an initial investigation of N-glycoproteins in complex biological samples and facilitates the identification of potential biomarkers of bladder cancer in noninvasively obtained human urine.

Markers of diabetic nephropathy

It is well established that the detection of microalbuminuria in a patient with diabetes mellitus indicates the presence of glomerular involvement in early renal damage. Recent studies have demonstrated that there is also a tubular component to renal complications of diabetes, as shown by the detection of renal tubular proteins and enzymes in the urine. In fact, tubular involvement may precede glomerular involvement, as several of these tubular proteins and enzymes are detectable even before the appearance of microalbuminuria. This review looks at the studies reported so far on serum and urinary markers of diabetic nephropathy, both glomerular and tubular, and their roles in the early detection of renal damage. The advantages and disadvantages of some of these markers are also discussed. The markers reviewed include (1) glomerular--transferrin, fibronectin, and other components of glomerular extracellular matrix, and (2) tubular--low molecular weight proteins (beta 2 microglobulin, retinol binding protein, alpha 1 microglobulin, urine protein 1), other proteins such as Tamm-Horsfall protein, beta 2 glycoprotein-1, urinary enzymes (N-acetyl-beta-D-glucosaminidase, cholinesterase, gamma glutamyltranspeptidase, alanine aminopeptidase), and tubular brush-border antigen.

Quantitative immunological determination of 12 plasma proteins excreted in human urine collected before and after exercise

Urine was collected from 6 healthy male adults at rest and from 20 male adults after a marathon race (25 miles). The concentrated urines were quantitatively analyzed, by single radial immunodiffusion, for their content in 12 different plasma proteins: tryptophan-rich prealbumin, albumin, alpha(1)-acid glycoprotein, alpha(1)-antitrypsin, ceruloplasmin, haptoglobin, Gc-globulin, transferrin, hemopexin, beta(2)-glycoprotein I, gammaA-globulin, and gammaG-globulin.Albumin, gammaA-globulin, and gammaG-globulin represent the major part of the plasma proteins detected in normal urine excreted by humans at rest (12, 0.5, and 2.5 mg respectively, out of a total excretion of 17.5 mg of plasma proteins per 24 hr). The other plasma proteins were excreted at a lower rate (< 0.4 mg/24 hr). The relative content of tryptophan-rich prealbumin, alpha(1)-antitrypsin, Gc-globulin, transferrin, and gammaG-globulin was lower in normal urine than in normal serum, whereas that of alpha(1)-acid glycoprotein, beta(2)-glycoprotein I, and gammaA-globulin was higher. The ratio of gammaG-globulin to gammaA-globulin was 4.9:1. When plotted on a logarithmic scale, no direct relationship between the molecular weight of a protein and the value of its renal clearance could be observed.Strenuous exercise increased (up to 50-fold) the excretion of plasma proteins which represent 82% of the total proteins found in urine, instead of 57% in urine collected from humans at rest. There was particularly a significant rise of tryptophan-rich albumin, albumin, alpha(1)-acid glycoprotein, transferrin, gammaA-globulin, and gammaG-globulin (0.26, 127, 11.8, 3.3, 1.2, and 2.0 mug respectively, out of a total excretion of 167 mug of plasma proteins per min). The ratio of gammaG-globulin to gammaA-globulin was 16:1. After exercise, the renal clearance of proteins increased from 2 to 40 times, but, as for the urine of normal subjects at rest, no direct relationship between molecular weight and renal clearance could be observed.

Concanavalin A-captured glycoproteins in healthy human urine

Both the urinary proteome and its glycoproteome can reflect human health status, and more directly, functions of kidney and urinary tracts. Because the high abundance protein albumin is not N-glycosylated, the urine N-glycoprotein enrichment procedure could deplete it, and urine proteome could thus provide a more detailed protein profile in addition to glycosylation information especially when albuminuria occurs in some kidney diseases. In terms of describing the details of urinary proteins, the urine glycoproteome is even a better choice than the proteome itself. Pooled urine samples from healthy volunteers were collected and acetone-precipitated for proteins. N-Linked glycoproteins enriched with concanavalin A affinity purification were separated and analyzed by SDS-PAGE-reverse phase LC/MS/MS or two-dimensional LC/MS/MS. A total of 225 urinary proteins were identified based on two-hit criteria with reliability over 97% for each peptide. Among these proteins, 94 were identified in previous urine proteome works, 150 were annotated as glycoproteins in Swiss-Prot, and 43 were predicted as glycoproteins by NetNGlyc 1.0. A number of known biomarkers and disease-related glycoproteins were identified. Because changes in protein quantity or the glycosylation status can lead to changes in the concanavalin A-captured glycoprotein profile, specific urine glycoproteome patterns might be observed for specific pathological conditions as multiplex urinary biomarkers. Knowledge of the urine glycoproteome is important in understanding kidney and body function.

Specific and sensitive determination of pregnancy-specific beta 1-glycoprotein by radioimmunoassay. A new pregnancy test

A specific and highly sensitive radioimmunoassay (R.I.A.) for determination of pregnancy-specific beta 1-glycoprotein (S.P.1) in human plasma, urine, amniotic fluid, and breast milk has been developed. The minimum detection limit of S.P.1 was 8 mug/1 of sample. The assay was applied to plasma and/or urine samples from 8 women in early pregnancy. S.P. 1 was detected in the plasma of all three women obtained within 14 days of ovulation, the earliest positive result being at 7 days. In another woman plasma was negative at day 18 and positive by day 22. In the three remaining women plasma S.P.1 was detected when measured within 24 to 36 days of ovulation. S.P.1 was detected in four urine samples obtained between 20 and 28 days after ovulation. S.P.1 was also measured in breast milk, amniotic fluid, cord blood, and plasma of women with ectopic gestation and trophoblastic disease. It is suggested that the assay of S.P.1 may have important advantages over existing systems for detection and monitoring of early pregnancy.

Urine glycoprotein crystal growth inhibitors. Evidence for a molecular abnormality in calcium oxalate nephrolithiasis

One reason that some people are prone to calcium oxalate nephrolithiasis is that they produce urine that is subnormal in its ability to inhibit the growth of calcium oxalate crystals. We have identified in human urine a glycoprotein (GCI) that inhibits calcium oxalate crystal growth strongly, and at low concentrations (10(-7) M); in this study, we have isolated GCI molecules from the urine of normal people and patients with calcium oxalate stones. GCI from stone formers is abnormal in three ways: it contains no detectable gamma-carboxyglutamic acid (Gla), whereas normal GCI contains 2-3 residues of Gla per mole; about half of the GCI in urine of patients inhibits crystal growth 4-20 times less than normal GCI as judged by its performance in a kinetic growth assay, in vitro; at the air-water interface, patient GCI has a film collapse pressure approximately half of normal. GCI molecules from the urine of patients with calcium oxalate nephrolithiasis are intrinsically abnormal, and these abnormalities could play a role in the genesis of stones.

Evaluation of circulating cathodic antigen (CCA) urine-tests for diagnosis of Schistosoma mansoni infection in Cameroon

BACKGROUND

The Kato-Katz is the most common diagnostic method for Schistosoma mansoni infection. However, the day-to-day variability in host egg-excretion and its low detection sensitivity are major limits for its use in low transmission zones and after widespread chemotherapy. We evaluated the accuracy of circulating cathodic antigen (CCA) urine-assay as a diagnostic tool of S. mansoni. In comparison, a low sensitive CCA test (CCA-L) was assessed.

METHODOLOGY

THE STUDY WAS CONDUCTED IN THREE SETTINGS: two foci with single S. mansoni infections (settings A and B), and one mixed S. mansoni - S. haematobium focus (setting C). Stool and urine samples were collected from school-children on three consecutive days. Triplicate Kato-Katz readings were performed per stool sample. Each urine sample was tested with one CCA and only the first urine sample was subjected to CCA-L. Urine samples were also examined for S. haematobium eggs using the filtration method and for microhaematuria using urine reagent strips. Overall, 625 children provided three stool and three urine samples.

PRINCIPAL FINDINGS

Considering nine Kato-Katz thick smears as 'reference' diagnostic test, the prevalence of S. mansoni was 36.2%, 71.8% and 64.0% in settings A, B and C, respectively. The prevalence of S. haematobium in setting C was 12.0%. The sensitivities of single Kato-Katz, CCA and CCA-L from the first stool or urine samples were 58%, 82% and 46% in setting A, 56.8%, 82.4% and 68.8% in setting B, and 49.0%, 87.7% and 55.5% in setting C. The respective specificities were 100%, 64.7% and 100%; 100%, 62.3% and 91.3%; and 100%, 42.5% and 92.0%. Mixed infection with S. haematobium did not influence the CCA test results for S. mansoni diagnosis.

CONCLUSIONS/SIGNIFICANCE

Urine CCA revealed higher sensitivity than CCA-L and triplicate Kato-Katz, and produced similar prevalence as nine Kato-Katz. It seems an attractive method for S. mansoni diagnosis.

beta2-glycoprotein-I (apolipoprotein H) and beta2-glycoprotein-I-phospholipid complex harbor a recognition site for the endocytic receptor megalin

Screening of serum by using a surface plasmon resonance analysis assay identified beta2-glycoprotein-I/apolipoprotein H as a plasma component binding to the renal epithelial endocytic receptor megalin. A calcium-dependent megalin-mediated beta2-glycoprotein-I endocytosis was subsequently demonstrated by ligand blotting of rabbit renal cortex and uptake analysis in megalin-expressing cells. Immunohistochemical and immunoelectron microscopic examination of kidneys and the presence of high concentrations of beta2-glycoprotein-I in urine of mice with disrupted megalin gene established that megalin is the renal clearance receptor for beta2-glycoprotein-I. A significant increase in functional affinity for purified megalin was observed when beta2-glycoprotein-I was bound to the acidic phospholipids, phosphatidylserine and cardiolipin. The binding of beta2-glycoprotein-I and beta2-glycoprotein-I- phospholipid complexes to megalin was completely blocked by receptor-associated protein. In conclusion, we have demonstrated a novel receptor recognition feature of beta2-glycoprotein-I. In addition to explaining the high urinary excretion of beta2-glycoprotein-I in patients with renal tubule failure, the data provide molecular evidence for the suggested function of beta2-glycoprotein-I as a linking molecule mediating cellular recognition of phosphatidylserine-exposing particles.

Tamm-Horsfall urinary glycoprotein. The subunit structure

1. Subunit molecular weights of 76000-82000 were obtained for native and alkylated Tamm-Horsfall glycoprotein by gel filtration on Sephadex G-200 in the presence of sodium dodecyl sulphate. 2. A further estimate of the subunit molecular weight of 79000+/-4000 was obtained by disc gel electrophoresis in sodium dodecyl sulphate. 3. A minimum value of the chemical molecular weight of 79000+/-6000 was obtained from the number of N-terminal amino acids released by cyanogen bromide cleavage of the glycoprotein. 4. Similar values were obtained for the subunit molecular weight of Tamm-Horsfall glycoprotein from patients with cystic fibrosis. 5. On ultracentrifugation both in 1.0% sodium dodecyl sulphate and in 70% formic acid, Tamm-Horsfall glycoprotein sedimented as a single component, slightly faster than serum albumin. 6. On reduction of the disulphide bonds the same subunit molecular weight was obtained, which suggested that these bonds are intrachain.

Solitary bone and extramedullary plasmacytoma

Less than 5% of patients with a plasma cell dyscrasia present with a single bone (SBP) or extramedullary plasmacytoma (EMP) without evidence of systemic disease (normocalcemia, absence of anemia, preservation of uninvolved immunoglobulins, or renal disease attributable to myeloma). Diagnosis requires biopsy confirmation of a monoclonal plasma cell infiltrate from a single site. The treatment of choice for both entities is radiotherapy given with curative intent (> 4000 cGy) resulting in long term disease-free survival in approximately 30% of patients with SBP and 65% of patients with EMP.

Urinary CD133+ extracellular vesicles are decreased in kidney transplanted patients with slow graft function and vascular damage

Extracellular vesicles (EVs) present in the urine are mainly released from cells of the nephron and can therefore provide information on kidney function. We here evaluated the presence of vesicles expressing the progenitor marker CD133 in the urine of normal subjects and of patients undergoing renal transplant. We found that EV expressing CD133 were present in the urine of normal subjects, but not of patients with end stage renal disease. The first day after transplant, urinary CD133⁺ EVs were present at low levels, to increase thereafter (at day 7). Urinary CD133⁺ EVs significantly increased in patients with slow graft function in respect to those with early graft function. In patients with a severe pre-transplant vascular damage of the graft, CD133⁺ EVs did not increase at day 7. At variance, the levels of EVs expressing the renal exosomal marker CD24 did not vary in the urine of patients with end stage renal disease or in transplanted patients in respect to controls. Sorted CD133⁺ EVs were found to express glomerular and proximal tubular markers. These data indicate that urinary CD133⁺ EVs are continuously released during the homeostatic turnover of the nephron and may provide information on its function or regenerative potential.

Evaluation of circulating cathodic antigen (CCA) urine-cassette assay as a survey tool for Schistosoma mansoni in different transmission settings within Bugiri District, Uganda

Diagnosis of schistosomiasis at the point-of-care (POC) is a growing topic in neglected tropical disease research. There is a need for diagnostic tests which are affordable, sensitive, specific, user-friendly, rapid, equipment-free and delivered to those who need it, and POC is an important tool for disease mapping and guiding mass deworming. The aim of present study was to evaluate the relative diagnostic performance of two urine-circulating cathodic antigen (CCA) cassette assays, one commercially available and the other in experimental production, against results obtained using the standard Kato-Katz faecal smear method (six thick smears from three consecutive days), as a 'gold-standard', for Schistosoma mansoni infection in different transmission settings in Uganda. Our study was conducted among 500 school children randomly selected across 5 schools within Bugiri district, adjacent to Lake Victoria in Uganda. Considering results from the 469 pupils who provided three stool samples for the six Kato-Katz smears, 293 (76%) children had no infection, 109 (23%) were in the light intensity category, while 42 (9%) and 25 (5%) were in the moderate and heavy intensity categories respectively. Following performance analysis of CCA tests in terms of sensitivity, specificity, negative and positive predictive values, overall performance of the commercially available CCA test was more informative than single Kato-Katz faecal smear microscopy, the current operational field standard for disease mapping. The current CCA assay is therefore a satisfactory method for surveillance of S. mansoni in an area where disease endemicity is declining due to control interventions. With the recent resolution on schistosomiasis elimination by the 65th World Health Assembly, the urine POC CCA test is an attractive tool to augment and perhaps replace the Kato-Katz sampling within ongoing control programmes.

Improved sensitivity of the urine CAA lateral-flow assay for diagnosing active Schistosoma infections by using larger sample volumes

BACKGROUND

Accurate determination of Schistosoma infection rates in low endemic regions to examine progress towards interruption of transmission and elimination requires highly sensitive diagnostic tools. An existing lateral flow (LF) based test demonstrating ongoing infections through detection of worm circulating anodic antigen (CAA), was improved for sensitivity through implementation of a protocol allowing increased sample input. Urine is the preferred sample as collection is non-invasive and sample volume is generally not a restriction.

METHODS

Centrifugal filtration devices provided a method to concentrate supernatant of urine samples extracted with trichloroacetic acid (TCA). For field trials a practical sample volume of 2 mL urine allowed detection of CAA down to 0.3 pg/mL. The method was evaluated on a set of urine samples (n = 113) from an S. mansoni endemic region (Kisumu, Kenya) and compared to stool microscopy (Kato Katz, KK). In this analysis true positivity was defined as a sample with either a positive KK or UCAA test.

RESULTS

Implementation of the concentration method increased clinical sensitivity (Sn) from 44 to 98% when moving from the standard 10 μL (UCAA10 assay) to 2000 μL (UCAA2000 assay) urine sample input. Sn for KK varied between 23 and 35% for a duplicate KK (single stool, two slides) to 52% for a six-fold KK (three consecutive day stools, two slides). The UCAA2000 assay indicated 47 positive samples with CAA concentration above 0.3 pg/mL. The six-fold KK detected 25 egg positives; 1 sample with 2 eggs detected in the 6-fold KK was not identified with the UCAA2000 assay.

CONCLUSIONS

Larger sample input increased Sn of the UCAA assay to a level indicating 'true' infection. Only a single 2 mL urine sample is needed, but analysing larger sample volumes could still increase test accuracy. The UCAA2000 test is an appropriate candidate for accurate identification of all infected individuals in low-endemic regions. Assay materials do not require refrigeration and collected urine samples may be stored and transported to central test laboratories without the need to be frozen.