Elfadil Abass; Abdelhafeiz Mahamoud; Durria Mansur; Mehdi Mohebali; Abdollah el Harith
Volume 8, Issue 3 , September 2011, , Pages 150-158
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 ...
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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.
Durria Mansour; Elfadil M. Abass; Abdelhafeiz Mahamoud; Abdallah el Harith
Volume 6, Issue 4 , December 2009, , Pages 208-215
Abstract
Background: Until now, the comparison of the rK39 strip test (RKT) and direct ag-glutination test (DAT) for detection of visceral leishmaniasis (VL) is exclusively based on either positive or negative qualification of the reaction outcome. Objective: In this study, we compared the diagnostic performance ...
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Background: Until now, the comparison of the rK39 strip test (RKT) and direct ag-glutination test (DAT) for detection of visceral leishmaniasis (VL) is exclusively based on either positive or negative qualification of the reaction outcome. Objective: In this study, we compared the diagnostic performance of RKT and DAT for VL both qualitatively and semi-quantitatively. Methods: For comparison based on semi-quantitative grounds, the execution of RKT and DAT was according to the standard procedures. For comparison on semi-qualitative grounds with DAT, the RKT was ap-plied to aliquots from positive samples that were two-fold serially diluted in saline to determine, as for the DAT, the end-point reaction in RKT. Results: While qualita-tively both RKT and DAT demonstrated comparable reliability for VL detection (sen-sitivity = 96% and specificity = 98.7% or 99.3%), no significant correlation (r = 0.13) could be established between intensities of their positive reactions in 25 cases studied. A negative correlation was further determined in those 25 VL cases between the posi-tive intensities of the RKT and antibody levels measured semi-quantitatively with the same procedure (r = -0.36) or the DAT (r = -0.30). Irrespective of the low, moderate or high antibody levels measured with RKT (<1:8 and 1:16-1:32 >1:256) or DAT (< 1:25,600 and 1:51,200- 1:409,600 > 1:3,276,800) in patients with confirmed or uncon-firmed VL infection, exclusively strong positive intensities were obtained with RKT. Conclusion: For further optimizing diagnosis and simultaneously assessing magni-tude of immune response to L. donovani infection in Sudanese patients, the combined application of RKT and DAT is recommended.
