HEMAGGLUTINATION ASSAYS FOR THE DIAGNOSIS AND PREVENTION OF IGA ANAPHYLACTIC TRANSFUSION REACTIONS

Passive hemagglutination assays (PHA) may be used to detect IgA antibo dies to confirm clinical diagnoses of suspected IgA anaphylactic trans fusion reactions. Passive hemagglutination inhibition assays (PHIA) ma y be used to identify IgA-deficient blood donors whose plasma-containi ng components are transfused to prevent anaphylactic transfusion react ions in prospective recipients at risk because of the presence of IgA antibodies. Using a standard PHA, we detected class-specific anti-IgA in 76.3% of 80 IgA-deficient patients with a history of an anaphylacti c transfusion reaction, and in 21.7% of 97 asymptomatic IgA-deficient blood donors or their IgA-deficient family members. Using PHIA, we con firmed IgA deficiency (<0.05 mg/dL) for the donors of 525 plasma-conta ining blood components that were transfused without acute clinical rea ctions to 48 IgA-deficient recipients with anti-IgA and/or a history o f an anaphylactic transfusion reaction. The frequency of IgA-deficienc y with class-specific anti-IgA among 32,376 random blood donors was 0. 08% (1/1,200). The combined use of PHA for detecting anti-IgA and PHIA for measuring IgA concentration provides an effective and safe strate gy for the diagnosis and prevention of IgA anaphylactic transfusion re actions. However, PHA for anti-IgA lacks specificity for identifying p ersons who are truly at risk for significant anaphylactic transfusion reactions. The consequence is an overdiagnosis of IgA anaphylactic tra nsfusion reactions and an overestimation of the number of persons at r isk for IgA anaphylactic transfusion reactions because of the detectio n of an IgA antibody in their serum. (C) 1994 by The American Society of Hematology.