Prevalence and diagnostic evaluation of Strongyloides stercoralis infection among the Temiar Orang Asli in Kelantan, Malaysia: A Bayesian latent class analysis using molecular and serological methods.

Strongyloides stercoralis remains one of the most neglected soil-transmitted helminths because diagnosis is hindered by the lack of a reliable reference standard and the poor sensitivity of conventional parasitological methods. The true burden of infection among Malaysia's Orang Asli communities remains poorly defined. This population-based cross-sectional study determined the prevalence of S. stercoralis infection among 134 Temiar Orang Asli from two villages in Kelantan, Malaysia, and evaluated the diagnostic accuracy of molecular and serological assays using Bayesian latent class analysis (BLCA). Stool specimens were examined by direct microscopy, agar plate culture, Harada-Mori filter paper culture, and real-time PCR targeting the 18S rRNA gene, while plasma was tested using a recombinant NIE-based IgG4 rapid diagnostic test (IgG4-RDT) and the Bordier Strongyloides IgG ELISA. Because no single method was considered a gold standard, BLCA estimated the 'true' prevalence and diagnostic accuracy. Overall, 67.9% of participants had at least one intestinal parasitic infection, with polyparasitism in 38.8%, but no S. stercoralis larvae were detected by conventional methods. Crude positivity rates were 31.1% for IgG4-RDT, 34.8% for ELISA, and 46.2% for PCR. BLCA-estimated prevalence was 22.5% (95% CrI: 12.4-34.0%). The IgG4-RDT demonstrated the highest sensitivity (90.8%) and specificity (86.7%), outperforming ELISA (81.0%, 72.5%) and PCR (77.9%, 77.0%). Posterior predictive checks identified excess PCR-positive/serology-negative results, suggesting biologically meaningful diagnostic discordance. BLCA revealed a hidden burden and showed that the IgG4-RDT had the best diagnostic performance for community screening. Further investigation of PCR-serology discordance using species-specific molecular methods is warranted.