Detection of leishmanial antigen in the urine of patients with visceral leishmaniasis by a latex agglutination test

Diagnosis of visceral leishmaniasis (VL) is usually done by demonstration of parasites in tissue smears. However, obtaining these smears may be risky, painful, and difficult. Antibody-based diagnostics are limited by their inability to predict active disease. In this study, a new latex agglutination test (KAtex), which detects parasite antigen in freshly voided and boiled urine, was evaluated in patients with VL before the start (n = 382) and at the end of treatment (n = 273); 185 healthy controls from leishmaniasis-endemic region were also studied. The KAtex result was positive in 87% (95% confidence interval [CI] = 83.3-90.3). However, at the end of treatment only 3% (95% CI = 1.6-6.2) patients were positive. The specificity of the test was 99% and 2 of 185 healthy controls tested positive. Positive and negative predictive values were 0.994 and 0.788, respectively. KAtex is a promising test, and in a simplified and improved format it could be applied meaningfully in the diagnosis of VL.