Age-related changes in thrombopoietin in children: reference interval for serum thrombopoietin levels

We studied thrombopoietin (TPO, Mpl ligand) values using a sensitive ELISA in 254 serum samples obtained from disease-free children and adult voluntee rs. TPO was detected in all samples, and its values ranged widely from 0.25 to 9.18 fmol/ml. When analysed by dividing the subjects into 11 age groups , the mean TPO levels from birth to 1 month of age were increased (3.73-5.9 2 fmol/ml), The highest values were found 2 d after birth: TPO levels then gradually decreased to adult levels (0.83 fmol/ml). The relationship betwee n TPO values and platelet counts was not significant in all subjects (r = 0 .27) or in children alone (r = 0.12). in children >1 month of age a 95% ref erence interval for serum TPO values was determined from 0.58 to 3.27 fmol/ ml. A significant correlation was found between TPO values in serum and pla sma: serum TPO values = -0.257 + 4.039 x plasma TPO values (r = 0.951, P < 0.001, n = 22). This study is the first to report age dependent changes in blood TPO levels throughout child development. Serum TPO values were signif icantly high up to 1 month of age and were correlated with plasma TPO level s.