Serum albumin and albumin-based inflammatory-nutritional ratios as predictors of mortality in acute coronary syndrome: an updated systematic review and meta-analysis

Abstract Background Serum albumin is emerging as a useful marker for predicting outcomes in acute coronary syndrome (ACS). Considerable new evidence has appeared since the last review in 2020. We aimed to update the evidence on albumin and mortality. We also examined albumin-based inflammatory-nutritional ratios in ACS. Methods We searched PubMed, Embase, and Scopus from March 2019 through October 2025. We included studies examining serum albumin or albumin-based ratios (The Glasgow Prognostic Score GPS, red cell distribution width/albumin ratio RAR, blood urea nitrogen/albumin ratio BAR, and CRP/albumin ratio CAR) and mortality in ACS patients. We used random-effects meta-analysis with Hartung-Knapp adjustment. Study quality was assessed using the Newcastle–Ottawa Scale. The primary outcome was all-cause mortality assessed using categorical albumin comparisons. Results We included 17 studies with a total of 24,714 patients, of which 17,689 patients for categorical serum albumin outcome, 3,311 patients for continuous serum albumin outcome, and 3,714 patients for albumin-based inflammatory-nutritional ratios outcome. Low categorical serum albumin was associated with increased mortality (pooled effect of 2.06; 95% CI 1.40–3.03; P = 0.003; prediction interval 0.86–4.95; I 2 = 67.7, τ 2 = 0.122), with a single outlying study identified through heterogeneity quantification and influence diagnostics as the main contributor to between-study variance in the primary outcome. The association varied by ACS subtype (p = 0.034) and geographical regions (p < 0.001). Results remained consistent across sensitivity analyses (pooled effect range 1.73–2.27). Few studies examined albumin-based ratios, but individual ratios showed promising results. Conclusions Low categorical serum albumin approximately doubles mortality risk in ACS patients, reinforcing previous evidence. Albumin-based inflammatory-nutritional ratios represent a promising approach for enhanced risk stratification warranting further investigation. Review Registration PROSPERO Registration ID: CRD420251274883