Thrombocytopenia due to platelet glycoprotein IIb/IIIa-reactive autoantibodies non-reactive with platelets from EDTA blood.

We describe 2 patients with thrombocytopenia and autoantibodies in the blood against platelet membrane glycoprotein (GP) IIb/IIIa, in whom reactivity of the antibodies with their antigen was greatly diminished in the presence of sodium EDTA. One patient also showed a marked thrombocytopathy, suggesting a functional blocking of GP IIb/IIIa by these autoantibodies. These observations show that some immunologically important autoantibodies can easily be missed in routine serological investigations in which EDTA blood is used, obscuring the autoimmune nature of a thrombocytopenia and possibly of a thrombopathy as well.