Sensitivity and Specificity of a Urine Circulating Anodic Antigen Test for the Diagnosis of <i>Schistosoma haematobium</i> in Low Endemic Settings

<div><p>Background</p><p>Elimination of schistosomiasis as a public health problem and interruption of transmission in selected areas are key goals of the World Health Organization for 2025. Conventional parasitological methods are insensitive for the detection of light-intensity infections. Techniques with high sensitivity and specificity are required for an accurate diagnosis in low-transmission settings and verification of elimination. We determined the accuracy of a urine-based up-converting phosphor-lateral flow circulating anodic antigen (UCP-LF CAA) assay for <i>Schistosoma haematobium</i> diagnosis in low-prevalence settings in Zanzibar, Tanzania.</p><p>Methodology</p><p>A total of 1,740 urine samples were collected in 2013 from children on Pemba Island, from schools where the <i>S</i>. <i>haematobium</i> prevalence was <2%, 2–5%, and 5–10%, based on a single urine filtration. On the day of collection, all samples were tested for microhematuria with reagent strips and for the presence of <i>S</i>. <i>haematobium</i> eggs with microscopy. Eight months later, 1.5 ml of urine from each of 1,200 samples stored at -20°C were analyzed by UCP-LF CAA assay, while urine filtration slides were subjected to quality control (QCUF). In the absence of a true ‘gold’ standard, the diagnostic performance was calculated using latent class analyses (LCA).</p><p>Principal Findings</p><p>The ‘empirical’ <i>S</i>. <i>haematobium</i> prevalence revealed by UCP-LF CAA, QCUF, and reagent strips was 14%, 5%, and 4%, respectively. LCA revealed a sensitivity of the UCP-LF CAA, QCUF, and reagent strips of 97% (95% confidence interval (CI): 91–100%), 86% (95% CI: 72–99%), and 67% (95% CI: 52–81%), respectively. Test specificities were consistently above 90%.</p><p>Conclusions/Significance</p><p>The UCP-LF CAA assay shows high sensitivity for the diagnosis of <i>S</i>. <i>haematobium</i> in low-endemicity settings. Empirically, it detects a considerably higher number of infections than microscopy. Hence, the UCP-LF CAA employed in combination with QCUF, is a promising tool for monitoring and surveillance of urogenital schistosomiasis in low-transmission settings targeted for elimination.</p>