Dot enzyme-linked immunosorbent assay (Dot-ELISA): Comparison with standard ELISA and complement fixation assays for the diagnosis of human visceral leishmaniasis

Abstract

The dot enzyme-linked immunosorbent assay (Dot-ELISA), standard ELISA and the complement fixation (CF) tests were compared in the serodiagnosis of African visceral leishmaniasis (kala-azar). Assay sensitivity was determined using sera from 44 patients with parasitologically confirmed kala-azar. Using the Dot-ELISA, 42 of 44 patients (95%) were positive at a reciprocal titer of ⩾ 32 (titer range 512–524 288). In the standard ELISA technique, 43 of 44 patients (98%) were positive (titer range 32–32 768). At a reciprocal titer of ⩾ 8 in the CF test, 35 patients (80%) were positive, 1 (2%) was negative and 8 patients (18%) showed anticomplemenatry (AC) activity (titer range 8–2048). Specificity, determined using 33 sera from healthy individuals not living in endemic areas, was 97% in both the Dot-ELISA and the standard ELISA (32 of 33 sera); in the CF test, all sera were negative except 1 (3%) which showed AC activity. Sera from patients with Chagas' disease cross-reacted in the Dot-ELISA up to a titer of 512. In the standard ELISA, cross-reactions occurred mainly using sera from patients with Chagas' disease, malaria and syphilis, and to a lesser extent with sera from amebiasis, schistosomiasis and trichinosis patients. Overall titer agreement in replicate experiments was highest in the Dot-ELISA (89%), followed by the standard ELISA (80%) and the CF test (72%).