Comparison of the erythropoietin response in children with aplastic anemia, transient erythroblastopenia, and iron deficiency.

To assess the effects of decreased erythrocyte production on the levels of serum erythropoietin in children, we measured simultaneous hemoglobin concentrations and erythropoietin in 18 children with iron deficiency anemia, 17 children with transient erythroblastopenia of childhood (TEC), and 7 children with aplastic anemia. In all but two patients (one with TEC; one with aplastic anemia), erythropoietin was measured at diagnosis, before institution of specific therapy for the anemia. There was a statistically significant inverse linear correlation between log10 erythropoietin and hemoglobin values for all patient groups (r = 0.904 to 0.912; p less than 0.005). A comparison of the slopes of the regressions for each patient group by analysis of covariance revealed a significantly steeper slope for the iron deficiency group (-0.553) versus the TEC (-0.287) and aplastic anemia (-0.256) groups (p = 0.0001). The difference in erythropoietin levels appeared greatest in patients whose presenting hemoglobin level was greater than 5 gm/dl. Decline in serum erythropoietin levels was more precipitous in the less severely anemic patients with iron deficiency anemia than in the patients with TEC or aplastic anemia. These data reveal quantitative and qualitative differences in the relationship between serum erythropoietin and hemoglobin levels when children with severe iron deficiency anemia versus those with TEC or aplastic anemia are considered, even though all three conditions are characterized by hypoproliferation of erythrocytes.