Detection of antibodies to malaria: comparison of results with ELISA, IFAT, and crossed immunoelectrophoresis.

194 sera from Vietnamese refugees and 100 pairs of corresponding maternal and cord sera from Liberia were examined for malaria-IgG antibodies by enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence microscopy (IFAT). For both tests the antigen was prepared from P. falciparum cultures. 44% of the Vietnamese sera were positive in the ELISA and 36% in the IFAT, but results were discordant in 36% of cases. The Liberian sera were all reactive in the IFAT and 95% were reactive in the ELISA. Overall, there was a significant correlation (p less than 0.001) between reciprocal IFAT titer and ELISA extinction value. With both tests, cord serum was generally slightly less reactive than corresponding maternal serum. Results of the two tests on 19 pairs of maternal and cord sera were compared with the number of anti-malaria precipitins detected by crossed immunoelectrophoresis. A positive correlation (p less than 0.01) between ELISA extinction values and numbers of precipitating antibodies was found. It is concluded that ELISA is at least as useful as IFAT for epidemiology and blood donor screening.