Immunochromatographic strip-test detection of anti-K39 antibody in Indian visceral leishmaniasis

Stored sera from 429 Indian subjects were assayed to extend the analysis of the accuracy of immunochromatographic strip-test detection of anti-K39 antibody in the non-invasive diagnosis of visceral leishmaniasis (VL). All 225 samples from patients with proven Leishmania infection tested positive [estimated sensitivity = 100%; 95% confidence interval (CI)=98%-100%]. Sera from 99 of the 100 symptomatic patients with other diseases were non-reactive (estimated specificity = 99%; CI = 94%-100%). However, samples from 13 of the 104 apparently healthy controls showed positive strip-test results (estimated specificity = 88%; CI = 79%-93%), yielding an overall specificity of 93% (190/204; CI = 88%-96%). If applied in a practical clinical setting (on symptomatic patients in whom active VL is suspected and other common infections have been excluded), strip testing of serum for anti-K39 antibody should be both sensitive and specific for diagnosing VL in India.