RESUMEN
OBJECTIVES: To determine the frequency of alloimmunization against human platelet antigens (HPAs) and human leucocyte antigen class 1 (HLA1) in multiparous women and multi-transfused patients. METHODS: This prospective study was conducted between January and August 2013, on 50 multiparous women with no history of previous blood transfusion recruited from the Obstetrics and Gynecology Clinic, and 50 patients, who received multiple platelet transfusions, recruited from the Hematology/Oncology Ward, King Khalid University Hospital, Riyadh, Saudi Arabia. RESULTS: The frequency of alloimmunization among multiparous pregnant women was 76%, as follows: 16% against HLA1 only, 8% against HPAs only, 52% against both HPAs and HLA1 antigens. In multi-transfused patients, the rate of alloimmunization was 42% as follows: 2% against HLA1 only, 22% against HPAs only, 18% against both HPAs and HLA1 antigens. The frequency of alloimmunization increases with the number of pregnancies, but not with the number of platelet transfusions. CONCLUSION: Alloimmunization against HPAs and HLA1 is very common among Saudi multiparous women and multi-transfused patients, which encourages the search for the extent of the possible complications in the fetus and newborn and in multitransfused patients and how to prevent their occurrence.