Objective To measure serum thrombopoietin(TPO)levels in thrombocytopenic conditions of aplastic anemia(AA)and idiopathic thrombocytopenic purpura(ITP)and explore the clinical significance of the changes of TPO levels.Methods Serum TPO concentration was determined in AA(n=13),ITP(n=20)and normal controls(n=17)by using an enzyme linked immunosorbent assay(ELISA).Results Serum TPO level in AA patients was much higher than that in normal controls[(683\^48?414\^73)ng/L vs (99\^41?73\^84)ng/L,P0 05].Furthermore,there was an inverse correlation between TPO concentration and platelet count in AA patients(r=-0\^71,P