Platelet Thromboplastic Function in Polycythæmia and Thrombocythæmia

SUMMARY The platelet thromboplastic function levels in patients with primary disease of the bone marrow (polycythæmia vera and primary thrombocythæmia) were compared with the findings in patients whose polycythæmia or thrombocytosis was due to a definable underlying disorder. Of the patients with untreated polycythæmia vera, irrespective of the platelet count, 71% showed reduced platelet thromboplastic function, compared with only 12% of patients with secondary polycythæmia which was uncomplicated by either renal or liver disease. Similarly, the platelet thromboplastic function level was reduced in 100% of patients with untreated primary thrombocythæmia, compared with 47% of patients with elevated platelet numbers secondary to other associated diseases. The platelet thromboplastic function test was therefore useful in differentiating between primary and secondary polycythæmia. Normal platelet thromboplastic function virtually excluded a myeloproliferative disease (thrombocythæmia) in patients with raised platelet counts, irrespective of other hæmatological changes. The effect of 32 P in the two conditions due to primary disease of the bone marrow was to produce a rise towards normal platelet thromboplastic function. It is considered that the platelet defect in primary thrombocythæmia is a qualitative one, and not, as has been reported by others, a quantitative anticoagulant effect of high in‐vitro platelet numbers.