Plasma thrombopoietin levels in marrow transplant patients with veno-occlusive disease of the liver

Platelet transfusion requirements are higher among patients with veno-occlusive disease (VOD), compared to patients without VOD. One possible explanation is inadequate production of thrombopoietin (TPO), a protein synthesized in the liver. We prospectively studied 28 patients to test the hypothesis that plasma TPO levels were decreased in patients who developed VOD. Plasma TPO levels to day +30 were measured by ELISA (normal, 0.36 +/- 0.15 fmol/ml), VOD developed in 18/28 patients. Platelet transfusion requirements were significantly different in patients with and without VOD (97 +/- 46.1 units vs 51 +/- 33.2 units, P = 0.008). Plasma TPO levels were elevated at baseline (10.8 +/- 13.0 fmol/ml) and increased after transplant, with peak values of 32.3 +/- 10.3 fmol/ml at day +7. TPO levels were significantly higher at days +7 and +17 among patients with VOD than among those without VOD (P < 0.01). Regression analysis of TPO levels as platelet counts showed a significant inverse relationship. We conclude that TPO levels were higher in patients with VOD and were inversely correlated with platelet counts, suggesting that regulation of TPO levels was related to platelet mass. Thrombocytopenia in patients with VOD cannot be explained by inadequate hepatic synthesis of TPO.