Relationship of sEpo to Hb observed in 27 patients with hypoproliferative anemia having erythroid activity <0.6 times normal (○) versus 28 patients with β-thalassemia intermedia having erythroid activity >2 times normal (•). (A) Relationship of measured sEpo to Hb level. Multivariate ANOVA showed that, at any given Hb level, sEpo was higher in patients with low versus those with high erythroid activity (P < .0001). (B) Relationship of corrected sEpo to Hb level. Data are those of (A), but corrected sEpo levels have been used instead of the measured ones. Multivariate ANOVA showed no significant difference between the relationship in patients with low erythroid activity and that in subjects with high erythroid activity (P > .05).