Platelets and Thrombosis

To the Editor.— Dr Gurewich's article in the OctoberArchives(137:1362-1363, 1977) discussed the value of the detection of thrombosis stimulating the various products of the fibrinogen-thrombin interaction. Since the editorial is entitled Laboratory Diagnosis of Thrombosis, the contribution of platelets cannot be ignored. When platelets undergo the release reaction in vitro, they release, among other substances, β-thromboglobulin (βTG) and platelet factor 4 (PF4), which neutralizes heparin. These proteins come uniquely from platelets. How these substances are liberated in vivo is not known, but their presence in the plasma clearly indicates that platelets have undergone the release reaction or have been otherwise activated. Just as the products of clotting can be generated in clinical conditions, so it also is with platelets. Platelets are involved regularly in diffuse intravascular coagulation, in thrombosis, and usually in infection. The products of platelet activation might be expected in the plasma. A new radioimmunological assay