Author(s): Abass E, Mahamoud A, Mansour D, Mohebali M, El Harith A
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Abstract BACKGROUND: A β-mercaptoethnol (β-ME)-treated promastigote antigen of L. donovani was successfully employed in direct agglutination test (DAT) for the diagnosis of visceral leishmaniasis (VL). OBJECTIVE: The β-ME-treated antigen was further incorporated into an enzyme-linked immunosorbent assay set-up (β-ME ELISA) and evaluated for VL diagnosis against outcome of reference freeze-dried DAT (FD-DAT) and rK39 strip test (RKT) commercial kits. METHODS: Two-hundred and ninety-two sera from patients with high VL suspicion of whom 105 had confirmed L. donovani infection were tested. RESULTS: Relatively higher sensitivities of 93.3\% (95\% CI: 88.4-98.2) and 92.4\% (95\% CI: 87.3-97.5) were determined for β-ME ELISA and FD-DAT as compared to 83.8\% (95\% CI: 76.7-90.8) for RKT. Of 73 VL sera that scored maximum absorbance values (>0.81) in β-ME ELISA, 66 (90.4\%) tested at the highest agglutination titres (>1:51200) in FD-DAT as did 56 (76.7\%) also at comparable reaction intensities (3 + colour intensity) in RKT. Compared with FD-DAT (94.7\%, 95\% CI: 91.5-97.9) or RKT (93.0\%, 95\% CI: 89.3-96.6), lower specificity was estimated for β-ME ELISA (90.4\%, 95\% CI: 86.1-94.6). Based both on positive and negative microscopy for L. donovani in organ aspirates of all VL suspects enrolled (292), significantly higher correlation (p<0.01, 0.919) was established between β-ME ELISA and FD-DAT than between β-ME ELISA and RKT (p<0.01, 0.824). Taking into calculation the combined estimates of sensitivity, specificity, positive and negative predictive values, higher agreement (94.8\%) was determined between total performance of β-ME ELISA and FD-DAT than between that of β-ME ELISA and RKT (90.7\%). CONCLUSION: Based on results and merits discussed, we recommend application of this β-ME ELISA both for diagnosis of VL at laboratory level and confirmation of results obtained with DAT or RKT in the field.
This article was published in Iran J Immunol
and referenced in Journal of Clinical & Experimental Pathology