Is the erythropoietin-hematocrit feedback control operative in chronic renal failure?

Transfusion studies in 23 chronic uremic patients with low hematocrit (HCT) values showed that (1) the pretransfusional immunodetectable (id) serum erythropoietin (EP) levels were within the normal range for healthy people; (2) the posttransfusional idEP levels remained unchanged; (3) 3 patients with analgesic nephropathy and high pretransfusional bioassayed (bio) EP levels had markedly suppressed posttransfusional bioEP, 6 patients with other kidney diseases had undetectable bioEP levels; (4) the raised pretransfusional reticulocyte (RETI) counts were markedly reduced by transfusions in all patients. We conclude that, in chronic uremic patients with elevated pretransfusional levels of bioEP, the bioEP is positively correlated with the kinetics of RETI and negatively correlated with the HCT. This correlation was not found for idEP.