Blood urea nitrogen-to-creatinine ratio and prognosis of acute heart failure: more confounding factors should be considered

As blood urea nitrogen (BUN) and creatinine (Cr) are well-recognized biomarkers for estimation of glomerular filtration rate (GFR) since they are freely filtered at the glomerulus due to their small size. Cr is more preferred in clinical practice for this purpose because it is not reabsorbed in the renal tubules of the nephron, while approximately half of the BUN is reabsorbed after filtration (1). The magnitude of BUN reabsorption is greatly affected by neurohormonal activity. Therefore, BUN to Cr ratio (BUN/Cr) is usually regarded as a metric of neurohormonal activity. Since neurohormonal activity is associated with prognosis of acute heart failure (AHF) (2), it is reasonable to hypothesize that BUN/Cr is a potential prognostic factor for AHF.