Use of a platelet filter test in patients with thrombocytosis

In the differential diagnosis of primary and secondary thrombocytosis plate let function tests may play an important role. We examined the applicabilit y of a platelet filter test (shear-dependent platelet aggregation) as a too l, to differentiate primary thrombocytosis (cases with myeloproliferative d isorders) from secondary (reactive) thrombocytosis, The test was carried ou t in 53 patients suffering from myeloproliferative disorders associated wit h primary thrombocytosis and in 21 patients with other diseases complicated by secondary thrombocytosis. Using citrate as anticoagulant, the sensitivi ty of the O'Brien's test proved to be 77.1%, and its specificity 94.4%. Usi ng heparin as anticoagulant the sensitivity and specificity of the test wer e found to be also reliably high. Based on these studies we suggest the use of the O'Brien's filterometer as a screening test in the differential diag nosis in patients with elevated platelet count. In the case of normal resul ts, the causes of reactive thrombocytosis should be clarified first, while with abnormal results, haematological examination of the patients should be performed.