THE LATEX AGGLUTINATION-TEST - STANDARDIZATION AND COMPARISON WITH DIRECT AGGLUTINATION AND DOT-ELISA IN THE DIAGNOSIS OF VISCERAL LEISHMANIASIS IN INDIA

Laboratory diagnosis of visceral leishmaniasis (VL) is usually based o n the detection of Leishmania amastigotes in samples of bone marrow or splenic aspirate obtained by invasive procedures. Serological tests s erve as a useful adjunct and are especially valuable in early or highl y immune cases where amastigotes may be too scanty to be seen easily. The direct agglutination test (DAT) is generally considered the most s uitable of the four types of tests currently employed (IFAT, counter i mmuno-electrophoresis, ELISA and DAT). However, the latex agglutinatio n test (LAT) was recently reported to be a rapid and sensitive screeni ng tool for VL and one which could be carried out at the patient's bed side. Further standardization and evaluation of LAT has now revealed t hat although it is comparable with DAT and dot-ELISA in terms of sensi tivity it is far inferior because of cross-reactivity with other infec tions. This lack of specificity makes LAT unsuitable for routine diagn osis of VL even though it is rapid and sensitive. DAT still appears to be the best choice as a diagnostic tool, as it is very specific and d oes not require expensive equipment or reagents or much technical comp etence and the result can be visually I interpreted. These merits make DAT very suitable for the diagnosis of VL in endemic areas of India.