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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 of a satisfactory procedure to evaluate donors potentially exposed to malaria. Materials and methods: We evaluated a commercial ELISA for the detection of antibodies to malaria and compared it with an immunofluorescent antibody test (IFAT). Results: When 5,311 sera from routine non‐exposed donors were tested, 24 (0.45%) were positive by the ELISA, using a Plasmodium falciparum antigen. Seventeen were subjected to confirmatory testing but none were positive by IFAT. Of 1,000 donors potentially 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 patients attending the Hospital for Tropical Diseases in London with acute malaria were tested, 73% of those infected with P. falciparum were repeatably reactive for malarial antibodies by ELISA and 56% with Plasmodium vivax. Of 88 stored clinical sera tested by both IFAT and ELISA 56 were positive by IFAT and of these 52 (93°/0) were positive by ELISA. Conclusion: The ELISA is sufficiently sensitive and specific to screen at‐risk donors. Its use could safely retrieve 40,000 red cell units currently discarded each year in Great Britain.