Red cell distribution width to albumin ratio may be a useful prognostic marker in the critical care setting

1. Higher red cell distribution width to albumin ratio (RAR) values were associated nonlinearly with a higher mortality risk.

2. The predictive power of RAR alone was moderate but increased when combined with Sequential Organ Failure Assessment (SOFA) scores. 

Evidence Rating Level: 2 (Good)

Current scoring systems, such as the Sequential Organ Failure Assessment (SOFA), can help predict intensive care unit (ICU) mortality but are often complex and require multiple clinical inputs. Simpler prognostic markers are needed to complement existing tools to improve risk stratification. Red cell distribution width (RDW)-to-albumin ratio (RAR) is a novel composite marker with emerging evidence as a potential predictor of mortality across patients with diseases. However, its role in predicting mortality in the diverse ICU population remains unclear. This study thus examined the role of RAR as a predictor of mortality in ICU patients. This retrospective cohort study used data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database and included ICU patients aged 18-90 who were admitted between 2008 and 2022. The primary outcome was all-cause mortality within 28 days after ICU admission. In total, 24,568 ICU patients were included in the study (median [IQR] age = 66 [54-76] years; females [%] = 10,484 [42.67]). Higher RAR values were nonlinearly associated with a higher 28-day mortality risk (adjusted HR = 1.06, 95% CI 1.05–1.07, P < 0.001) and a significant nonlinear relationship (P < 0.001), with a sharp increase in mortality risk observed when RAR values exceeded approximately 5.0 (P for nonlinearity < 0.001). The predictive power of RAR for 28-day mortality was moderate (area under the curve (AUC) = 0.66, 95% CI 0.65–0.67) but improved when combined with SOFA scores (AUC = 0.74, 95% CI 0.72–0.76). Overall, this study found RAR alone has moderate predictive ability for mortality but increases prognostic accuracy when combined with SOFA scores, highlighting RAR’s potential as an adjunct to mortality risk assessment in the ICU setting. Future studies are needed to validate these findings across diverse populations.

Click to read the study in EJMR

Image: PD

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