ESSENTIAL THROMBOCYTHEMIA AT DIAGNOSIS - CAUSES OF DIAGNOSTIC EVALUATION AND PRESENCE OF POSITIVE DIAGNOSTIC-FINDINGS

The reasons for diagnostic evaluation and the clinical and laboratory data at diagnosis of 170 patients with essential thrombocythemia (ET) were studied retrospectively. The age distribution was 19-88 years (me dian 52 years), and 52 patients were under the age of 45 years. In 111 patients (65%) thrombocytosis was a chance finding, but the past hist ory of 37 of these patients revealed symptoms known to be related to E T. The diagnosis was based on a chance finding in a significantly high er proportion of female (74%) than male (53%) patients. The diagnosis of ET is based mostly on negative findings, i.e., on the exclusion of other causes of thrombocytosis, and positive diagnostic tests would be useful. We evaluated the presence of positive diagnostic findings of myeloproliferative disorders in ET. Splenomegaly was seen in 26% and a n abnormal karyotype in 5% of the patients. Abnormal megakaryocyte mor phology was seen in 80%, abnormal in vitro growth of hematopoietic pro genitors in 74%, and abnormal platelet function in 83% of the patients . Both in vitro cultures of hematopoietic progenitors and platelet fun ctions were studied in 36 patients, and in only two of these were both tests normal. We conclude that in most patients with ET the diagnosis can be strongly supported by positive findings, especially by in vitr o cultures of hematopoietic progenitors and studies of platelet functi on.