Strong inverse correlation between serum TPO level and platelet count in essential thrombocythemia

Serum thrombopoietin (TPO) levels in 50 essential thrombocythemia (Ei) pati ents were measured using a highly sensitive sandwich ELISA, In nine cases, TPO levels were measured at two points with different platelet counts. ET p atients showed significantly higher serum TPO levels (n = 59, 2.70 +/- 2.74 fmol/ml, P < 0.0001) than those of normal individuals (n = 29, 0.83 +/- 0. 36 fmol/ml). Twenty-three previously untreated ET patients also showed sign ificantly higher serum TPO levels (1.33 +/- 0.75 fmol/ml, P = 0.0066) than normal individuals. Extremely high serum TPO levels (5.46 +/- 3.68 fmol/mL) were observed in ET patients with normal platelet counts. Furthermore, a s trong inverse correlation was found between serum TPO levels and platelet c ounts in ET patients (R = -0.729, P < 0.0001), This inverse correlation als o held for each of nine cases with two-point TPO measurements, In the clini cal course of ET, megakaryocyte mass may parallel the platelet mass before and after chemotherapy. Although it is unknown whether overproduction of TP O exists or not in ET, total platelet and megakaryocyte mass, i.e., the tot al number of c-Mpl, may play a role to regulate serum TPO levels, Am. J, He matol, 63:131-135, 2000. (C) 2000 Wiley-Liss, Inc.