Clinical use of β‐thromboglobulin levels in diagnosing and treating consumptive and immune thrombocytopenia

Plasma β-thromboglobulin (β-TG), a platelet-specific protein, is a marker of intravascular platelet degranulation. We measured plasma β-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 β-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 β-thromboglobulin levels that were not elevated. Two patients with thrombotic thrombocytopenic purpura achieved clinical remission associated with a decrease in β-TG level to the normal range. Plasma β-thromboglobulin determination can be useful in determining the mechanism of thrombocytopenia when bone marrow examination demonstrates adequate megakaryocyte numbers.