Direct Agglutination Test Based on Freeze Dried Antigen from Leishmania donovani : Development and Comparative Evaluation with Aqueous Antigen and Recombinant rK_<39> Antigen for Sero-diagnosis of Visceral Leishmaniasis

Direct Agglutination Test (DAT) and rK_ strip tests have been considered useful for the diagnosis of Visceral Leishmaniasis (VL). DAT with aqueous (AQ) antigen has drawbacks like limited stability and requirement of uninterrupted cold chain till its end use. The present study describes the development of modified DAT based on freeze-dried (FD) antigen from L. donovani promastigotes. FD antigen was found to be stable for 24 months at 56℃. FD antigen, AQ antigen and rK_ strips were evaluated with 708 serum samples of different disease spectrum of VL. Findings revealed that both FD as well as AQ antigen showed 96.5% sensitivity and 100% specificity, where as rK_ strip test exhibited 86% sensitivity and 100% specificity. Statistically the performance of FD and AQ antigen was better than rK_ (P