qualitative and semi-quantitative comparison of an rk39 strip test and direct agglutination test for detection of anti-leishmania donovani antibodies in the sudan

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 (1:256) 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.