Comparison of stool examination, urine rapid diagnostic test (RDT), and stool PCR for diagnosing Opisthorchis viverrini infection

Urine antigen testing for Opisthorchis viverrini is under consideration for screening in Thailand, yet surveys report positivity rates far exceeding stool-based prevalence. We evaluated a lateral-flow urine rapid diagnostic test (OV-RDT) among 239 men in a northern Thai correctional facility, where O. viverrini and Haplorchis taichui are co-endemic, and residents had been without raw-fish exposure for at least one month. We examined single stool specimens using Kato–Katz and phosphate-buffered saline–ethyl acetate concentration; species-differentiating ITS2-PCR served as the reference standard. PCR detected O. viverrini in 6.7% (16/239), whereas the OV-RDT was positive in 77.0% (124/161) of participants with valid urine. Sensitivity was 75.0% (95% CI 42.8–94.5) and specificity 22.8% (16.3–30.4); likelihood ratios were close to one, and band intensity did not discriminate PCR status. Specificity was similar under composite reference definitions, after correction for imperfect PCR sensitivity, and among participants with no helminth detected (21.3%). Taenia spp. were found in 12.1% and were not associated with OV-RDT positivity. In this low-prevalence, co-endemic setting, OV-RDT positivity corresponded poorly with molecularly confirmed infection, suggesting that confirmatory testing is needed before results inform prevalence estimates or treatment decisions.