HPA-1a (PLA1 Platelet Antigen) Genotyping (PLA2 Polymorphism Detection)

Whole blood

5 mL

Blue-top (sodium citrate) tube, lavender-top (EDTA) tube, or yellow-top (ACD) tube

Individuals negative for the HPA-1a (PL^A1) antigen are at risk for developing antibodies to this antigen as may occur in neonatal alloimmune thrombocytopenia and post-transfusion purpura.

Amplification refraction mutation system (ARMS) polymerase chain reaction (PCR)

This is a molecular test to genotype the HPA-1 DNA sequence. The wild-type platelet glycoprotein HPA-1a (PL^A1) is present in approximately 98% of the general population. A single nucleotide polymorphism changes the antigenic determinant from HLA-1a (PL^A1) to HPA-1b (PL^A2). Alloimmune platelet-associated immunoglobulin (PAIg) antibodies arise when there is an antigenic challenge to individuals who lack specific platelet antigens. Neonatal alloimmune thrombocytopenia is a serious, potentially fatal disease affecting fetuses and neonates. Fetal expression of platelet antibodies foreign to the mother result in maternal formation of antiplatelet antibodies with subsequent destruction of fetal platelets. Approximately 80% of these antibodies form in neonatal alloimmune thrombocytopenia anti-HPA-1a (PL^A1). This same antibody is implicated in cases of post-transfusion purpura, in which the recipient of a platelet-containing blood product develops antiplatelet antigens that destroy not only the transfused platelet, but native platelets as well. The mechanism of this destruction is poorly understood.