An evaluation of urine-CCA strip test and fingerprick blood SEA-ELISA for detection of urinary schistosomiasis in schoolchildren in Zanzibar

To develop better monitoring protocols for detection of urinary schistosomiasis during ongoing control interventions, two commercially available diagnostic tests – the urine-circulating cathodic antigen (CCA) strip and the soluble egg antigen enzyme-linked immunosorbent assay (SEA-ELISA) – were evaluated for detection of Schistosoma haematobium infections in 150 schoolchildren from Zanzibar. The children originated from five primary schools representative of different levels of disease endemicity across the island; using standard urine filtration assessment with microscopy, mean prevalence of S. haematobium was 30.7% (95% confidence interval (CI) = 23.4–38.7%) and a total of 35.3% (95% CI = 27.7–43.5%) and 8.0% (95% CI = 4.2–13.6%) children presented with micro- and macro-haematuria, respectively. Diagnostic scores of the urine-CCA strip were not satisfactory, a very poor sensitivity of 9% (95% CI = 2–21%) was observed, precluding any further consideration. By contrast, the performance of the SEA-ELISA using sera from fingerprick blood was good; a sensitivity of 89% (95% CI = 76–96%), a specificity of 70% (95% CI = 60–79%), a positive predictive value of 57% (95% CI = 45–69%) and a negative predictive value of 90% (95% CI = 86–98%) were found. At the unit of the school, a positive linear association between prevalence inferred from parasitological examination and SEA-ELISA methods was found. The SEA-ELISA holds promise as a complementary field-based method for monitoring infection dynamics in schoolchildren over and above standard parasitological methods.