Superiority of dat over elisa as a diagnostic and seroepidemiological tool for the diagnosis of Indian kala-azar.

ABSTRACT

The aim of this study was to evaluate two methods for the diagnosis of Kala-azar. The sera of 160 individuals were evaluated by ELISA using soluble antigen and direct agglutination test (DAT) for Kala-azar. These were categorized as 100 cases of clinically and parasitologically confirmed Kala-azar and 60 controls. The controls included clinically suspected but parasitologically not confirmed Kala-azar patients (10), endemic normals (15), non-endemic normals (19), typhoid fever (10) and malaria (15). The positivity rate amongst the clinically and parasitologically confirmed Kala-azar patients by ELISA and DAT were 93% and 98% respectively. Out of 10 clinically suspected Kala-azar cases three showed positive reaction in ELISA and two in DAT. Of the endemic normals, one case was found positive by both the tests whereas ELISA was found positive in one additional case. DAT did not show any cross reactivity with malaria while ELISA was found positive in one case. Both endemic normals and typhoid fever cases showed no reaction by both tests. ELISA showed a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 93%, 90%, 93% and 90% respectively while for DAT these values were 98%, 95%, 98 and 95% respectively. The diagnostic accuracy for ELISA and DAT was found to be 91.9% and 96.9%, respectively. The present study shows that DAT is a simple, sensitive, specific and cost effective test with high PPV and NPV along with approximately 97% diagnostic accuracy and is comparable to ELISA. It may be applied for the routine diagnosis as well as seroepidemiological study of Kala-azar.