Is the thrombopoietin assay useful for differential diagnosis of thrombocytopenia? Analysis of a cohort of 160 patients with thrombocytopenia and defined platelet life span

Background: Thrombopoietin (TPO), the major hormone controlling platelet pr oduction, has been measured in thrombocytopenias with discordant results. T he aim of our work was to assess the value of the TPO assay for differentia l diagnosis of thrombocytopenias in a large cohort of patients classified a ccording to the results of their platelet isotopic study. Methods: We measured TPO (R&D Systems) in serum of 160 thrombocytopenic pat ients referred to our department for platelet life span isotopic studies. W e classified patients as follows: (a) idiopathic or autoimmune thrombocytop enia group (ITP, patients with increased platelet destruction and shortened platelet life span; n = 67); (b) pure genetic thrombocytopenia group (pati ents with decreased platelet production, normal platelet life span, and wit hout bone marrow aplasia; n = 55); (c) bone marrow aplasia group (BM; patie nts with decreased platelet production, normal platelet life span, and bone marrow aplasia; n = 13). Results: In patients with pure genetic thrombocytopenia, TPO (median, 55 ng /L) was not different from TPO in patients with ITP (median, 58 ng/L) or co ntrols (n = 54; median, 51 ng/L). Only in patients with bone marrow aplasia was TPO significantly higher (median, 155 ng/L) and negatively correlated to the platelet count (r(2) = 0.5014). Conclusions: Although the median serum TPO is increased in thrombocytopenia with decreased platelet production from bone marrow aplasia, it does not d ifferentiate patients with pure genetic thrombocytopenia from those with IT P. (C) 2001 American Association for Clinical Chemistry.