Local Production of a Liquid Direct Agglutination Test as a Sustainable Measure for Control of Visceral Leishmaniasis in Sudan.

A prerequisite for the control of visceral leishmaniasis (VL) is the accessibility to reference diagnostics. The high price of the freeze-dried direct agglutination test (FD-DAT) and the short shelf-life time of the rK39 strip test (rK39) have limited the application of these tests in Sudan. An original liquid DAT (LQ-DAT) with high reproducibility compared with the FD-DAT and rK39 has been routinely produced in our laboratory since 1999. In this study, a 3.4-year-old batch (of more than 90 test batches produced to date) was chosen to validate the diagnostic performance of this test against microscopy, FD-DAT, and rK39 in 96 VL and 42 non-VL serum samples. Relatively higher sensitivity (95/96, 99.0%) was recorded for the LQ-DAT than for the FD-DAT (92/96, 95.8%) and rK39 (76/96, 79.2%), probably because of the use of the endemic autochthonous Leishmania donovani isolate as the antigen. Experience with the LQ-DAT, its low cost of production, ease of providing this test, and diagnostic reliability compared with the FD-DAT suggest that widescale implementation of the LQ-DAT can contribute to sustainable VL control in Sudan.