Improvement of direct agglutination test (DAT) for laboratory diagnosis of visceral leishmaniasis in Brazil.

We previously standardized the direct agglutination test (DAT) to detect anti-Leishmania chagasi promastigote antibodies (DAT-LPC) with good sensitivity and specificity for diagnosing visceral leishmaniasis (VL). In this paper, we present a technical upgrade by introducing some modifications into the antigen preparation. This antigen was evaluated in DAT (DAT-Mod) using 61 sera samples from VL patients and 96 samples from patients with other diseases. The DAT-Mod presented a cut-off of 1:100, satisfactory reproducibility (VC <5.8), sensitivity of 93.4%, specificity of 96.9%, and diagnostic efficiency of 95.5%. The improvement in antigen preparation reduced inter-batch variations and resulted in a high test performance.