Platelet Antibodies, Indirect

This is the primary test for detection of platelet-specific antibodies. It is not recommended for the diagnosis of immune thrombocytopenic purpura (ITP). This test will detect both allo and autoantibodies, but will not distinguish between them. Results of this test should be used in conjunction with clinical findings and other serological tests. Antibodies directed to antigens found on platelets are associated with many different clinical situations. Immune thrombocytopenic purpura (ITP) is a destructive thrombocytopenia caused by autoantibodies. Neonatal alloimmune thrombocytopenia (NATP) and post-transfusion purpura (PTP) are diseases where thrombocytopenia is caused by platelet-specific alloantibodies. HLA alloantibodies do not cause thrombocytopenia, but are commonly associated with refractoriness to platelet transfusions.

This test is designed to detect antibodies to platelet glycoproteins IIb/IIIa (HPA-1a/1b [PlA1 and PlA2], HPA-3a/3b, and HPA-4a), Ia/IIA (HPA-5a/5b), Ib/IX, and IV. In addition, this test will also detect antibodies to HLA Class I antigens (HLA-A-B).

Testing for neonatal alloimmune thrombocytopenia should be performed using a maternal serum, since platelet antibody may not be detected in a neonatal serum. False negative results are common in infant samples.