Detection and quantification of soluble egg antigen in urine of Schistosoma haematobium-infected children from Kenya.

Abstract

Abstract. While research on alternative diagnostic and morbidity markers for infection with Schistosoma haematobium has been going on for a long time, egg counts continue to be used as the gold standard, and infection intensity is thought to reflect the severity of the disease. However, this relationship is not always clear and fluctuation in egg output makes it difficult to classify prevalence correctly. The use of circulating adult worm antigen detection as an alternative diagnostic technique has been applied with varying success. However, this is a measure of worm burden and does not reflect the tissue egg load(s). In the present study we have used an assay that detects soluble egg antigen (SEA) in urine of S. haematobium-infected children, and we have evaluated the applicability of the assay as a diagnostic and morbidity indicator. To evaluate this assay, we have studied a group of 470 children from two schools (Tsunguni and Kibaokiche) in the Coast province of Kenya; 84.8% and 77% were egg-positive while the percentage positive as determined by the SEA-ELISA were 78.8% and 76.2% in Tsunguni and Kibaokiche, respectively. In both schools, SEA levels in urine of S. haematobium-infected children significantly correlated with egg counts (Pearson's r ϭ 0.73, P Ͻ 0.0001) and with hematuria (Spearman's r ϭ 0.65, P Ͻ 0.0001). In addition, urinary tract pathology as determined by ultrasound significantly correlated with the SEA levels in urine (Spearman's r ϭ 0.3, P Ͻ 0.001). The SEA-ELISA compared well with microhematuria within egg count classes and with egg counts within hematuria classes.Detection of Schistosoma haematobium ova in urine of infected individuals remains the leading method for the direct diagnosis of the disease, and the intensity of infection expressed as number of eggs per 10 ml of urine is thought to reflect the worm burden. However, a homogeneous distribution of S. haematobium ova in urine is difficult to achieve, 1 while day-to-day and circadian variation in egg excretion may lead to incorrect estimates in prevalence and intensity of infection. Additionally, the relationship between egg counts and pathology is not always clear. 2 The presence and intensity of microhematuria, proteinuria, and leukocyturia are semi-quantitative measures of S. haematobium infection, and these parameters were found to correlate with infection intensity. 3-5 However, variations dependent on geographic area, endemicity, cultural practices, age, sex, and even time of the day exist, limiting the application of hematuria as a diagnostic tool. 6-9 Ultrasound scanning of the urinary tract remains the gold standard for pathology. This technique has been applied in the field and correlates well with standard direct and indirect measurements of S. haematobium morbidity. 10,11 However, ultrasound equipment is expensive and requires trained physicians to handle the equipment and interpret the results, limiting its use under field conditions. These shortcomings have led to the search for alternative quantitative diagnostic meth...

Urine circulating soluble egg antigen in relation to egg counts, hematuria, and urinary tract pathology before and after treatment in children infected with Schistosoma haematobium in Kenya.

“…We have previously described an assay detecting SEA in the urine of S. haematobium-infected individuals and have found significant correlations with egg counts, hematuria, and ultrasound-detectable pathology. 9,13 In the current study, similar correlations were also observed both before therapy with praziquantel and 18 months after therapy. Clearance of SEA from the urine was slower compared with egg counts and levels increased significantly six months after treatment, about two months later than egg counts; SEA levels continued to increase in parallel with egg counts and overall pathology.…”

“…10 Two schools were selected for the study, Tsunguni with an initial prevalence of 86% and Kibaokiche with a prevalence of 77%. From the group previously described, 9 117 children participated in all follow-up examinations: 52 from Tsunguni and 65 from Kibaokiche of whom 59 were boys and 58 were girls (age range ϭ 6-15 years, median ϭ 9 years).…”

“…A monoclonal antibody-based sandwich ELISA was used for the quantification of SEA in urine of the infected children as described previously. 9,12 The lower detection limit for this ELISA was 16-31 ng/ml and samples with absorbency values above the mean of the buffer rows plus two standard deviations were considered positive for SEA. The assay has a specificity of 93% and a sensitivity of 90% and shows little reactivity with S. mansoni-infected and negative control urine samples.…”

“…9 In this study, we examine the dynamics of SEA in urine in a group of school children before and after treatment and compare these with intensity of infection, hematuria, and ultrasound-detectable pathology.…”

Sensitive and specific enzyme-linked immunosorbent assay for the diagnosis of Wuchereria bancrofti infection in urine samples.

“…To facilitate sample collection for immunodiagnosis, urine samples have been used to test for schistosomiasis, [8][9][10][11] malaria, 12 leishmaniasis, 13 Chagas disease, 14 and filariasis. [15][16][17] In human filariasis, the usefulness of immunoglobulin (Ig) G4 in the diagnosis of filarial infections has been reported.…”