DIAGNOSTIC AND DIFFERENTIAL CRITERIA OF ESSENTIAL THROMBOCYTHEMIA ANDREACTIVE THROMBOCYTOSIS

Among the chronic myeloproliferative disorders essential thrombocythem ia (ET) is known to be a distinct clinical entity in which an excessiv e number of morphologically and functionally abnormal platelets are pr oduced. The clonal nature of the disease is well established. Based on a review of the literature the present authors propose the following novel criteria for the diagnosis of ET: A1. Platelet count in excess o f 600 x 10(9)/L. A2. No increase in red-cell mass (RCM) in the presenc e of stainable iron in the bone marrow or failure of iron trial (RCM < 36mL/kg in males and <32mL/kg in females; or RCM <25% above mean norma l predicted value). A3. No Philadelphia chromosome. A4. Megakaryocyti c hyperplasia (=increased megakaryocyte number and size) in histologic al sections of bone marrow and/or increased megakaryocytic ploidy (two -color flow cytometry); no collagen fibrosis. B1. Splenomegaly on isot opic scan or echogram. B2. Unstimulated growth of BFU-E and/or CFU-Meg present. B3. Normal ESR/fibrinogen. The diagnosis of ET is considered to be established if A1 + A2 + A3 + A4 or A1 + A2 + A3 + two B-criter ia are fulfilled.