Blood urea nitrogen (BUN) levels may be better indicators of anemia risk than estimated glomerular filtration rate (eGFR) in patients with nondialysis-dependent chronic kidney disease (NDD-CKD), according to investigators.

Dong-Wan Chae, MD, of Seoul National University in Korea and colleagues studied the independent effects of BUN. Among 2196 patients in the KoreaN Cohort Study for Outcome in Patients With Chronic Kidney Disease (KNOW-CKD), 1169 had no anemia at baseline. Over a follow-up period of 37.5 months, new cases of anemia developed in 414 patients in this group (35.4%). In an adjusted multivariable Cox regression analysis, each 1 mg/dL increase in BUN level and BUN residual both were significantly associated with a 2% increased risk for anemia, the investigators reported in PLoS One. (BUN residuals were obtained from the fitted curve between BUN and eGFR.) In patients with stage 3 CKD, BUN, but not eGFR, was significantly associated with increased anemia risk.

BUN and BUN residuals both showed relationships with daily protein intake in patients with NDD-CKD. Patients with high BUN might have higher levels of protein-derived uremic toxins that interfere with erythropoiesis.

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“This study is the first study to demonstrate the effects of BUN independent of eGFR on anemia in [NDD-CKD] using data from large numbers of [patients] spanning all CKD stages in a prospective CKD cohort,” Dr Chae’s team stated.

“Higher BUN levels derived from inappropriately high protein intake relative to renal function were associated with low hemoglobin levels and the increased risk of anemia independent of eGFR in patients [with NDD-CKD],” the investigators explained.


Kim HJ, Kim TE, Han M, et al. Effects of blood urea nitrogen independent of the estimated glomerular filtration rate on the development of anemia in non-dialysis chronic kidney disease: The results of the KNOW-CKD study. PLoS One. 2021;16(9). Published online September 10, 2021. doi:10.1371/journal.pone.0257305