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

Abstract

Abstract. 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.

Validation of in-house liquid direct agglutination test antigen: the potential diagnostic test in visceral Leishimaniasis endemic areas of Northwest Ethiopia

“…Our in-house AQ-DAT had a sensitivity (97.3%) comparable to FD-DAT (99.1%) and rK39-ICT (96.5%), taking microscopy as gold standard. This is similar to a study done in Sudan in which AQ-DAT, FD-DAT, and rK39 showed a sensitivity of 99, 95.8, and 79.2%, respectively [14]. Similarly, studies conducted in Brazil and Sudan documented better sensitivity of FD-DAT (98-100%) compared to rK39-ICT (85.7-90%) [20,21].…”

“…In contrast, another study from the Northeast of Sudan showed, lower sensitivity for FD-DAT (84%) compared with rK39-ICT (93%) [22]. Overall, the observed differences in sensitivity among studies could be due to the strain variation that affects the gene expression level of The specificity of the in-house AQ-DAT, FD-DAT and rK39-ICT were 98.8, 97.5 and 93.2%, respectively, which is in line with findings of the studies done in Sudan which revealed 100, 100 and 97.6%, respectively [14,21]. The AQ and FD-DAT, also showed similar specificity with the findings reported from the United Kingdom, Brazil and Sudan [20,21,23].…”

“…Among them, DAT was shown to be more sensitive, specific and reproducible [12,13]. The production technique of the DAT antigen is not patented, and elsewhere the use of local strains of VL causing strain makes it even more sensitive and specific [14,15]. Yet, the national program is highly dependent on foreign aid to purchase DAT and this leads for unnecessary delays due to import regulations and processes.…”

The Diagnostic Accuracy of Direct Agglutination Test for Serodiagnosis of Human Visceral Leishmaniasis: A Systematic Review with Meta-analysis

“…Some studies performed DAT using both freeze-dried (FD) and aqueous (AQ) antigen (18,19). No signi cant difference in the sensitivity of the DAT (FD and AQ) was found.…”

“…In overall, studies had a wide geographical distribution and were carried out in different countries including Brazil (20)(21)(22), Ethiopia (14,16,23), India (19,(24)(25)(26)(27)(28)(29), Iraq (30), Iran (31-33), Saudi Arabia (15), Sudan (18,(34)(35)(36)(37), Turkey (17) and Venezuela (38).…”