Latent class analysis of diagnostic tests for visceral leishmaniasis in Brazil

Objective To estimate the sensitivities and specificities of different diagnostic tests for visceral leishmaniasis (VL) using latent class analysis (LCA). Methods This study was performed using data from a prospective study conducted in four Brazilian states from May 2004 to May 2007. Five diagnostic tests for VL were evaluated in 285 VL cases and 119 non-cases: microscopy, indirect fluorescence antibody test (IFAT), enzyme-linked immunosorbent assay using recombinant K39 antigen (rK39-ELISA), direct agglutination test (DAT) and the rK39 rapid test. Results Microscopy showed sensitivity of 77.0% (CI: 71.581.5) and specificity of 99.0% (CI: 94.099.7). The IFAT and the DAT showed similar sensitivities, 88.3% (CI: 84.092.0) and 88.5% (CI: 84.192.0), respectively, but the DAT had a higher specificity (95.4%, CI: 89.298.1) than did the IFAT (83.0%, CI: 75.088.2). The rK39-ELISA and the rK39 rapid test showed sensitivities of 99.0% (CI: 96.399.6) and 94.0% (CI: 90.196.3), and specificities of 82.5% (CI: 75.088.3) and 100% (CI: 97.0100.0%), respectively. Conclusions Considering the lack of an adequate reference standard, LCA proved to be a useful tool in validating diagnostic methods for VL. The DAT and the rK39 rapid test showed better performance. Thus, clinically suspected cases of VL in a Brazilian endemic area could be treated based on the positivity of one of these tests.