A comparative evaluation of the performance of commercially available rapid immunochromatographic tests for the diagnosis of visceral leishmaniasis in Bangladesh

Background: Accurate and early diagnosis of Visceral Leishmaniasis (VL) is a prerequisite for proper treatment and restricting disease propagation in enldemic foci. An rK39 antigen-based immunochromatographic test is now recommended for its diagnostic accuracy and operational feasibility at point of care. In endemic regions of Bangladesh, rK39 or rKE16 antigen-based Rapid Diagnostic Tests (RDTs) are routinely performed on whole blood for diagnosis of VL. However, manufacturer's instructions require use of serum. Therefore, we wanted to assess whether the diagnostic accuracy of these RDTs is as good on whole blood as on serum. Methods: We evaluated and compared the sensitivity and specificity of five different commercially available RDTs on whole blood and on serum. We enrolled 30 VL patients, 35 endemic healthy controls and 30 Tuberculosis (TB) patients in our study from Mymensingh, a hyper-endemic region in Bangladesh. Results: The sensitivity of all RDTs ranged between 96.67 % (95 % CI: 82.72-99.44 %) and 100 % (95 % CI: 96.34-100 %). The specificity ranged between 93.85 % (95 % CI: 84.97-98.26 %) and 98.46 % (95 % CI: 91.69-99.74 %), except for the Onsite leishmania Ab (Rev B) kit which showed markedly lower specificity (31.25-58.46 %). There was no significant difference in sensitivity and specificity between blood and serum. The Cohen kappa index (k >0.97) indicated excellent agreement. Conclusions: We conclude from the study that the use of blood for RDT in lieu of serum is appropriate for diagnosis of VL in peripheral endemic regions provided the manufacturer recommendations are followed and the RDT is of good quality.