Clinical Applications of Platelet Antibody and Antigen Testing

Immune thrombocytopenia occurs when antibodies targeting specific glycoproteins (GPs) on the platelet surface lead to their destruction. Tests of the patient’s platelets and serum for antibodies and typing of DNA for human platelet alloantigens (HPA) can be helpful in confirming a clinical diagnosis of immune thrombocytopenia. A thorough workup includes 1) serum tests using intact platelets; 2) antigen-capture assays to identify the specific HPA targeted by platelet antibodies; and 3) HPA genotyping of the patient’s DNA. For patients suspected of having autoimmune thrombocytopenia, a direct test of an eluate of the patient’s platelets for autoantibodies targeting the most common GPs can be performed. Properly interpreted platelet serologic test results, taken together with a good clinical history and other laboratory data, will ensure a more accurate diagnosis and appropriate treatment.