BACKGROUND Patients with advanced renal dysfunction have comorbidities, including anemia, as a consequence of reduced production of erythropoietin. However, little is known about the renal response to early decreases in estimated glomerular filtration rate (eGFR) before the onset of anemia. We therefore investigated the hemoglobin concentration across subtle declines in renal function stratified by cardiorenal risk factors, in subjects with eGFR ≥50 mL/min/1.73 m(2).

METHODS Based on the data from routine health checkups in tertiary university hospitals during the last 15 years, 145 865 adult subjects were identified.

RESULTS Hemoglobin levels among eGFR Groups 2-6 (50 ≤ eGFR < 100 mL/min/1.73m(2)) were significantly higher compared to eGFR group ≥100 mL/min/1.73m(2) (P < 0.001), and the highest level of mean hemoglobin was seen at eGFR 50-59 mL/min/1.73m(2). The mean hemoglobin level of subjects with eGFR 50-59 mL/min/1.73m(2) and eGFR ≥ 100 mL/min/1.73m(2) were 13.36 [95% confidence interval (CI): 13.33-13.40] g/dL versus 12.92 (95% CI: 12.88-12.95) g/dL in women (P < 0.001); in men, 15.60 (95% CI: 15.57-15.63) g/dL versus 15.15 (95% CI: 15.11-15.18) g/dL (P < 0.001). Among each eGFR group, hemoglobin levels were higher in subjects with hypertension (P < 0.001 in both genders), diabetes mellitus (P < 0.001 in both genders) and components of MS (P < 0.003 in both genders) compared to subjects without these conditions.

CONCLUSION Hemoglobin concentration may be slightly higher across subtle declines in renal function and the presence of cardiorenal risk factors in early CKD stages.