Comparative Evaluation of Aqueous and Freeze Dried Antigen for Sero-diagnosis of VL and PKDL Cases by DAT

The efficacy of aqueous and freeze dried (FD) antigen was evaluated by direct agglutination test (DAT) for sero-diagnosis of visceral leishmaniasis. A total of 16 samples collected from 5 confirmed Kala-azar (KA) cases, 6 cases 2 each of filariasis, malaria, leprosy and 5 non-endemic healthy subjects were used in determination of cut off titre of both the antigens in DAT. A 1:800 for aqueous and 1:400 dilution for FD DAT antigen was found as cutoff values for differential diagnosis of KA cases from control subjects. Both antigens revealed 100% correlation in terms of sensitivity and specificity in diagnosis of KA cases and healthy subjects at these titres. Using both antigens and the cut off titres, sera from 26 individuals collected from different categories of leishmaniasis viz. Kala-azar pre-treatment 10, Kala-azar post-treatment 10, HIV-KA co-infection 1 and PKDL 5 were evaluated by DAT. Both the antigens showed equal sensitivity and specificity in diagnosis of different categories of leishmaniasis. The study concludes that though aqueous antigen showed equal sensitivity and specificity but FD antigen which is stable at 56^oC do not require cold chain whereas aqueous antigen is unstable at room temperature and require proper cooling to retain its antigenic activity as studied in between day 1 and day 14, so the FD antigen should be used for routine diagnosis of KA cases particularly in field condition.