A simple and economical direct agglutination test for serodiagnosis and sero-epidemiological studies of visceral leishmaniasis

Abstract
A simple and economical direct agglutination test for the detection of visceral leishmaniasis is described. Trypsin-treated, Coomassie Brilliant Blue-stained, formalin-preserved promastigotes were used as antigen in re-usable V-well microtitre plates. In 21 patients with recent kala-azar, titres of 1:51200 or higher were found. Cured kala-azar patients treated 4 to 14 months before testing, showed titres in the range of 1:3,200 to >1:51,200. Healthy and diseased controls had titres below 1:1,600 with the exception of African trypanosomiasis patients who showed titres of 1:200 to 1:12,800, overlapping with the titres of cured kala-azar patients. Where trypanosomiasis is not a consideration, a titre of 1:1,600 could be considered indicative of visceral leishmaniasis, the sensitivity and specificity were then 100%. The test was applied to sera of 280 inhabitants of Baringo District, a known focus of visceral leishmaniasis in Kenya. When treated cases were included, the test showed a sensitivity of 100% and specificity of 99·3%. This test could be used in district hospitals and health centres in endemic areas as an aid in diagnosis of kala-azar and in the field for sero-epidemiological studies.