SERUM THROMBOPOIETIN (TPO) LEVELS IN PATIENTS WITH AMEGAKARYOCYTIC THROMBOCYTOPENIA ALE MUCH HIGHER THAN THOSE WITH IMMUNE THROMBOCYTOPENICPURPURA

We assayed serum thrombopoietin (TPO) levels in amegakaryocytic thromb ocytopenia (AMT) and immune thrombocytopenic purpura (ITP) patients by using a newly established enzyme-linked immunosorbent assay (ELISA). TPO levels in AMT patients were quite high (mean +/- SD = 13.7 +/- 11. 2 fmoles/ml, n = 4), whereas those in ITP patients were only slightly higher (1.25 +/- 0.39, n = 12) than those of the healthy donors (0.55 +/- 0.2, n = 20). Furthermore, in ITP patients no correlation was obse rved between platelet counts and serum TPO levels (correlation coeffic ient = 0.14). We further assayed serum TPO levels sequentially during steroid treatment in patients with AMT and ITP. In one AMT patient ser um TPO levels started to decrease in accordance with the increase of m egakaryocyte counts, which preceded the increase in platelet counts. H owever, in ITP patients serum TPO levels did not change significantly throughout the course of the treatment despite the recovery of platele t counts. Based on these findings, we conclude that serum TPO levels m ay be regulated al least in part by megakaryocyte counts.