Detection and identification of platelet antibodies in clinical disorders.

Serologic assays to detect and identify platelet-reactive antibodies have progressed from less sensitive and specific Phase I tests based on platelet functional endpoints through more sensitive Phase II assays that detect platelet-associated immunoglobulins, to highly specific Phase III assays that detect antibodies bound to alloantigens located on isolated platelet surface glycoproteins. Phase II and III assays are useful in the evaluation of patients with suspected platelet alloimmune syndromes neonatal alloimmune thrombocytopenia (NATP) and post-transfusion purpura (PTP) as well as in platelet crossmatching. Flow cytometry, a Phase II assay, can be modified to detect drug-dependent platelet-reactive antibodies. 14C-serotonin release, a Phase I assay and the platelet factor 4 ELISA, a Phase III assay, are now used to diagnose patients with heparin-induced thrombocytopenia (HIT). A sufficiently sensitive and specific assay to diagnose idiopathic (autoimmune) thrombocytopenia (ITP) remains elusive.