EVALUATION OF A MALARIA ANTIBODY ELISA AND ITS VALUE IN REDUCING POTENTIAL WASTAGE OF RED-CELL DONATIONS FROM BLOOD-DONORS EXPOSED TO MALARIA, WITH A NOTE ON A CASE OF TRANSFUSION-TRANSMITTED MALARIA

Background and objectives: Blood donations are often wasted for lack o f a satisfactory procedure to evaluate donors potentially exposed to m alaria. Materials and methods: We evaluated a commercial ELISA for the detection of antibodies to malaria and compared it with an immunofluo rescent antibody test (IFAT). Results: When 5,311 sera from routine no n-exposed donors were tested, 24 (0.45%) were positive by the ELISA, u sing a Plasmodium falciparum antigen. Seventeen were subjected to conf irmatory testing but none were positive by IFAT. Of 1,000 donors poten tially exposed in endemic areas 15 (1.5%) were repeatably reactive by ELISA. 10 of these were tested by IFAT and 2 were positive. When 150 p atients attending the Hospital for Tropical Diseases in London with ac ute malaria were tested, 73% of those infected with P. falciparum were repeatably reactive for malarial antibodies by ELISA and 56% with Pla smodium vivax. Of 88 stored clinical sera tested by both IFAT and ELIS A 56 were positive by IFAT and of these 52 (93 degrees/0) were positiv e by ELISA. Conclusion: The ELISA is sufficiently sensitive and specif ic to screen at-risk donors. Its use could safely retrieve 40,000 red cell units currently discarded each year in Great Britain.