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Aim: To study the association between hemoglobin, endogenous erythropoietin (EPO) levels and ferric parameters in kidney recipients not treated with EPO-stimulating agents., Materials and Methods: Transverse study of 219 kidney transplant outpatients. The median time after transplantation was 54 months (P(25-75), 23-107). We assessed blood counts, ferric parameters, EPO levels, renal function (MDRD-4), and adjuvant treatment. We performed a linear regression analysis to predict hemoglobin., Results: Median EPO values were 14.05 mUI/mL (P(25-75) = 10.2-19.7). Applying the formulas described by Beguin, kidney transplant recipients showed a low observed/expected ratio of erythropoietin and of transferrin. Considering anemia to be an hemoglobin of < 12 g/dL in women and < 13 g/dL in men, 24.2% of subjects were anemic (n = 53), including 2.3% with hemoglobin < 11 g/dL. Anemic patients displayed worse renal function (49.2 ± 18.5 versus 55.46 ± 16.58 mL/min/1.73 m(2) in nonanemic; P = .021). There were no differences in C-reactive protein. The patients receiving a combination of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARB) showed the highest prevalence of anemia compared with other groups (42.9%, P = .027). EPO levels were significantly lower among patients treated with these drugs (P = .041), without differences in transferrin and ferritin. The percentage of anemic patients treated with mammalian target of rapamycin inhibitors (mTORi) was 31% versus 22.2% among those not receiving these immunosuppressants (P = .23). Although there were no differences in hemoglobin levels, patients treated with mTORi, showed higher EPO levels (P = .005) and lower mean corpuscular volume (P < .001). Regarding the etiology of chronic kidney disease, less frequently anemic patients were those with polycystic kidney disease (8.6% versus 26.7% in the rest, P = .021). The formula obtained by multiple linear regression to calculate hemoglobin was: hemoglobin = 11829-0909 log (EPG level) - 0455 (if female) + 0.010 0.013 transferrin + 0.013 creatinine clearance (r = .424, P < .001)., Conclusions: Treatment with ACEI and/or ARBs seemed to produce a defect in the synthesis of EPO, while those treated with mTORi, a hyporesponsive state., (Copyright © 2012 Elsevier Inc. All rights reserved.)