Evaluation of rK28 antigen for serodiagnosis of visceral Leishmaniasis in India.

Antibody detection is a safely applied method at the wide scale in diagnosis of visceral Leishmaniasis (VL). In order to further advance serodiagnosis, the rK28 antigen has been recently introduced as a candidate for diagnosis of VL. We evaluated the sensitivity and specificity of the rK28 antigen in a micro-ELISA format in comparison to the rk39 antigen. The test was conducted on 252 parasitologically confirmed VL cases, 103 endemic healthy controls, 95 non-endemic healthy controls, 88 other infectious disease and 53 follow-up cases. Of 252 parasitologically confirmed VL cases, 251 cases were reported positive by rK28 antigen, yielding 99.6% sensitivity (95% CI, 0.97-0.99), which was similar to the sensitivity of rK39 ELISA (99.6%) (95% CI, 0.97-0.99). Specificity of the rK28 antigen in non-endemic and endemic healthy controls was 100% (95% CI 0.96-1) and 94.17% (95% CI, 0.88-0.97), respectively. In 88 different diseases, specificity was 95.45% (95% CI, 0.84-0.96). With the rK39 antigen, specificity of non-endemic and endemic controls and different diseases was 100% (95% CI 0.96-1), 92.23% (95% CI 0.85-0.96) and 96.59% (95% CI 0.90-0.98), respectively. Our results show that rK39 and rK28 antigens have similar sensitivity and specificity and rK28 can also be used as a serodiagnostic tool in the endemic population of Bihar.