Latent class analysis of diagnostic tests for visceral leishmaniasis in Brazil

Abstract

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: 71.5-81.5) and specificity of 99.0% (CI: 94.0-99.7). The IFAT and the DAT showed similar sensitivities, 88.3% (CI: 84.0-92.0) and 88.5% (CI: 84.1-92.0), respectively, but the DAT had a higher specificity (95.4%, CI: 89.2-98.1) than did the IFAT (83.0%, CI: 75.0-88.2). The rK39-ELISA and the rK39 rapid test showed sensitivities of 99.0% (CI: 96.3-99.6) and 94.0% (CI: 90.1-96.3), and specificities of 82.5% (CI: 75.0-88.3) and 100% (CI: 97.0-100.0%), 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.

Keywords: Leishmaniasis visceral; analyse de classe latente; análisis de clase latente; diagnosis; diagnostic; diagnóstico; latent class analysis; leishmaniose viscérale; visceral leishmaniasis.