Usefulness of thrombopoietin in the diagnosis of peripheral thrombocytopenias.

BACKGROUND AND OBJECTIVE Thrombocytopenia of peripheral origin is basically due to platelet destruction or splenic sequestration. Thrombopoietin (TPO) regulates platelet production stimulating megakaryocyte proliferation and maturation. The evaluation of TPO levels may be a useful tool in the diagnosis of thrombocytopenias of unknown origin. We tried to determine the value of TPO levels in some thrombocytopenias classically considered as peripheral. DESIGN AND METHODS Serum TPO levels and platelet counts were measured in 32 thrombocytopenic patients with liver cirrhosis (LC) and 23 with chronic hepatitis C (CHC) viral infection, in 54 patients with a clinical and serological diagnosis of autoimmune thrombocytopenic purpura (AITP), and in 88 patients infected with the human immunodeficiency virus (HIV). RESULTS Patients with LC, AITP and HIV had lower platelet counts than patients with CHC. The degree of thrombocytopenia did not, however, correlate with the TPO levels. HIV infected patients (246+/-304 pg/mL) and AITP patients (155+/-76 pg/mL) had higher TPO levels than controls (121+/-58 pg/mL). TPO levels in patients with CHC (125+/-40 pg/mL) did not differ from those in control subjects, but were slightly decreased in patients with LC (104+/-56 pg/mL). INTERPRETATION AND CONCLUSIONS Reduced TPO production could be involved in the development of thrombocytopenia in LC patients, but not in patients with early stages of CHC viral infection. HIV and AITP patients had slightly raised levels of TPO. As TPO levels are normal or slightly increased in most peripheral thrombocytopenias, these data alone are not sufficient to distinguish the different types of peripheral thrombocytopenia. They may, however, be a useful tool for differentiating some central and peripheral thrombocytopenias.