Evaluation of indirect immunofluorescent antibody test for detection of IgM specific antibodies in malaria.

Indirect immunofluorescent antibody test using Plasmodium falciparum antigen from in vitro culture was evaluated for detecting IgM antibodies in order to determine the feasibility of its application in serodiagnosis of malaria. Test was compared with the already adapted IgG-IIF test using the same antigen. It was found that none of the healthy controls and slide negative fever cases had malaria IgM antibodies whereas 8 per cent of healthy controls and 49.01 per cent of the slide negative fever cases had malaria IgG antibodies. The sensitivity of IgM-IIF test was 94.68 per cent and that of IgG-IIF test was 96.81 per cent. IgM antibodies could be detected very early even on the first day of fever and titre rose gradually with increasing number of days of illness before institution of treatment. The IgM antibodies, being short lasting are able to reflect recent infection. The test although highly sensitive and specific is laborious and expensive. Therefore, it may be used as a serodiagnostic test in advanced laboratories only for confirmation of selected slide negative cases.