SERUM ERYTHROPOIETIN AND ERYTHROID ACTIVITY IN VITAMIN-B-12 DEFICIENCY

We studied erythropoiesis in 31 patients with vitamin B-12 deficiency by measuring serum erythropoietin (s-Epo), serum transferrin receptor (s-TfR, taken as an index of: total erythroid activity), reticulocyte count, and;the reticulocyte maturation index (RMI). s-Epo and s-TfR we re measured with commercial immunoassays, whereas reticulocyte count a nd RMI were determined by flow cytometry. s-Epo (123+/-196 U/L) and s- TfR (4.1+/-2 mg/L) levels were increased in patients with vitamin B-12 deficiency. The absolute reticulocyte counts were decreased (29+/-18x 10(9)/L) with a relative increase in the most immature fractions (RMI: 29.6+/-18%). A significant negative relationship was found between s- Epo and Hb level (r = -0.65, p < 0.0001). On the average, however, s-E po was inappropriately low for the degree of anemia, since the observe d/predicted (O/P) s-Epo ratio was 0.80+/-0.28 in vitamin B-12 deficien cy vs 1.00+/-0.16 in a group of patients with iron deficiency anemia. It is concluded that at least a portion of patients with vitamin B-12 deficiency have serum erythropoietin levels that are inappropriately l ow for the degree of anemia. (C) 1997, Ferrata Storti Foundation.