The relationship between HbE/HbF ratio and Epo and sTfR in regularly transfused HbE/β thalassemics. In both cases, the ratio decreases with increasing sTfR and Epo levels, suggesting that the degree of reduction of HbF synthesis is proportional to the degree of erythroid suppression. The dotted lines follow 95% CI for the slope. The vertical line in (B) denotes in mean log sTfR in HbE trait (0.18). (A) %HbE/HbF = 5.6 − (1.41 × log Epo), R = −.44,P = .065. (B) %HbE/%HbF = 6.4 − (3.43 × log sTfR),R = −.53, P = .022.