Anemia and estimated glomerular filtration rates

Objective: To determine the relationship between the estimated glomerular filtration rate (eGFR) and the prevalence of anemia that has potential implications for reporting results of the eGFR. Methods: Serum creatinine and hemoglobin test results from 18,474 outpatients aged 50 years or older were reviewed. We calculated the eGFR using the Chronic Kidney Disease Epidemiology Collaboration equation (CKDEPI) and the Modification of Diet in Renal Disease equation (MDRD) and determined the odds of anemia (according to the World Health Organization definition) at various eGFR levels, adjusted for age and gender. Results: The lowest proportion of anemia was observed in those with an eGFR of 80-89 mL/min per 1.73 m² and 90-99 mL/min per 1.73 m² (MDRD and CKD-EPI respectively), with an increasing prevalence of anemia in those with either an eGFR of 60-69 mL/min per 1.73 m² or 100-109 mL/min per 1.73 m² calculated by either equation (p<0.05) with a dose-response effect. Conclusions: We found a U-shaped relationship between anemia and the eGFR, suggesting that values >60 mL per 1.73 m² should be reported. However, the clinical utility and potential side effects of reporting such values need to be determined. Also, these preliminary findings require confirmation by studies in other settings.