Clinical use of beta-thromboglobulin levels in diagnosing and treating consumptive and immune thrombocytopenia.

Plasma beta-thromboglobulin (beta-TG), a platelet-specific protein, is a marker of intravascular platelet degranulation. We measured plasma beta-thromboglobulin by radioimmunoassay in 13 patients with thrombocytopenia of various etiologies to determine whether or not the test is clinically useful in the differential diagnosis of thrombocytopenia. Four patients with intravascular platelet consumption (three with thrombotic thrombocytopenic purpura and one with vasculitis) had significantly higher plasma beta-thromboglobulin levels than four patients with extravascular platelet destruction due to idiopathic thrombocytopenic purpura. Five patients with thrombocytopenia and decreased numbers of megakaryocytes in the bone marrow also had beta-thromboglobulin levels that were not elevated. Two patients with thrombotic thrombocytopenic purpura achieved clinical remission associated with a decrease in beta-TG level to the normal range. Plasma beta-thromboglobulin determination can be useful in determining the mechanism of thrombocytopenia when bone marrow examination demonstrates adequate megakaryocyte numbers.