Serum erythropoietin concentrations in patients with anemia--preliminary hemoglobin-related reference ranges.

Serum erythropoietin (EPO) determination is useful in the diagnosis of renal anemia. In anemic patients with normal renal function increased EPO concentrations are typically found, however, so far hemoglobin-related reference ranges for serum EPO had not been established. In a cross-sectional manner we determined serum EPO in 280 patients with anemia and normal serum concentrations of creatinine and urea. Each 70 consecutive anemic patients with hemoglobin concentrations within four intervals were included (<8 g/dL; 8.1-9.0 g/dL; 9.1-10.0 g/dL; 10.1-11.0 g/dL). 97 patients were from surgical disciplines, 183 were from internal disciplines. Serum EPO was determined by use of an automated sandwich immunoassay that is standardized according to the WHO 2nd IRP 67/343. The ranges between the 20th and 80th percentile of EPO concentrations for the four specified hemoglobin intervals were as follows: Hb <8 g/dL, EPO 61.8-366 IU/L; Hb 8.1-9.0 g/dL, EPO 43.3-242 IU/L; Hb 9.1-10.0 g/dL, EPO 31.8-113 IU/L; Hb 10.1-11.0 g/dL, EPO 22.3-71.2 IU/L. Since no complete diagnostic evaluation of the patients' renal and respiratory functions was performed in this cross-sectional study we propose the 20th percentile of EPO concentrations as a preliminary hemoglobin-related reference range; serum EPO concentrations below this percentile speak for a contribution of EPO deficiency in the individual etiology of anemia.