THROMBOCYTOSIS IN ADULTS - ANALYSIS OF 777 PATIENTS

A total of 777 patients with thrombocytosis, defined as a platelet count of > 500 x 10(9) l-1, seen in a University hospital over a 1-year period, were studied prospectively for aetiology. The most frequent causes of thrombocytosis were infection (21.9 %), rebound thrombocytosis (19.4 %), tissue damage (17.9 %), chronic inflammatory disorders (13.1 %) and malignancy (5.9 %). Thrombocytosis associated with multiple causative factors, occurring simultaneously, was seen in 6.1 % of cases. Thrombocytosis of greater-than-or-equal-to 1 million x 10(9) l-1 was found most frequently in patients with multiple aetiological factors occurring at the same time, in myeloproliferative disorders, or in postsplenectomy patients.