Red blood cell alloantibodies after transfusion: factors influencing incidence and specificity.

BACKGROUND: Alloimmunization after exposure to red cell (RBC) alloantigens depends on genetic and acquired patient-related factors, dose and route of administration, and the immunogenicity of the antigen, but exact kinetics are still unknown. STUDY DESIGN AND METHODS: A 5-year retrospective multicenter study analyzing factors influencing the rate and specificity of RBC alloimmunization was performed, with special emphasis on the time interval between transfusion event and antibody detection. Included were clinically significant alloantibodies against the Rhesus, Kell, Duffy, Kidd, and MSs blood group systems.
RESULTS: Multivariate analysis involving 1710 immunized patients revealed that time interval between transfusion and antibody tests was strongly associated with the antibody specificity. Anti-Jk(a) and anti-Jk(b) were predominantly found in patients tested within 3 months, whereas anti-K and anti-Fy(a) were the most encountered antibodies at more than 5 years after transfusion. Of all immunized patients, new antibodies were detected within 14 days after transfusion in 299 patients (16.8%) and in 1479 patients (83.2%) after more than 14 days. Fifty percent of transfusion recipients were retested for alloimmunization because of a new transfusion indication. Eleven of 2932 patients (0.4%) retested up to 3 days after transfusion had formed new antibodies.
CONCLUSION: The time interval between transfusion and antibody test was associated with RBC antibody specificity. Because RBC antibody tests after transfusion are not routinely performed, many antibodies may (not) be detected at the time of a new transfusion event, posing the transfusion recipient at risk for transfusion delay or a (delayed) hemolytic transfusion reaction. Routine RBC antibody screening at set time intervals after transfusion would reduce these risks.