Additional Information

NIT results from maternal antibodies which cross the placenta and bind to the platelets of the fetus. The most common cause (80-90%) of this disease is maternal antibodies to the platelet antigen A1 which the mother lacks but the infant has inherited from the father. Several tests are done to investigate NAIT. The maternal platelets are screened for the presence of PLA1 (HPA-1a) antigen. In addition, the maternal serum is screened for general platelet antibodies. This screen detects antibodies to HLA antigens, which are found on platelets, and the common platelet specific antigens including A1. Maternal platelets are screened for higher then normal levels of platelet bound IgG to screen for maternal autoantibodies to platelets. Finally, if paternal blood is available, the maternal serum is tested specifically for antibodies to the paternal platelets. This will detect antibodies to antigens on the paternal platelets and potentially the baby’s platelets which may be very rare (low incidence antigens) – so rare that they are only found in a single family.