The CALLY index as a novel predictor of long-term mortality after coronary artery bypass grafting: an international multicenter retrospective cohort study

Abstract

Despite advances in perioperative care, risk stratification following cardiac surgery remains inaccurate. The C-reactive protein–albumin–lymphocyte (CALLY) index integrates inflammatory burden, nutritional reserve, and immune status. We aimed to evaluate the association between the CALLY index and short- and long-term all-cause mortality following coronary artery bypass grafting (CABG). We conducted an international, multicenter retrospective cohort study including 6,883 consecutive adult patients undergoing isolated CABG. The CALLY index was calculated using preoperative serum albumin, lymphocyte count, and C-reactive protein levels and analyzed as predefined tertiles and as a continuous variable. The primary endpoint was long-term all-cause mortality, and the secondary endpoint was 30-day mortality. Associations were assessed using Cox proportional hazards regression models stratified by center and adjusted for clinically relevant covariates. Restricted cubic spline analyses were performed to explore potential non-linear associations. Restricted mean survival time (RMST) was estimated at 5 and 10 years to quantify adjusted absolute survival differences. During a median follow-up of 79.7 months (interquartile range, 43.6–120.9), 623 long-term deaths (9.1%) and 96 30-day deaths (1.4%) occurred. 30-day mortality decreased progressively across increasing CALLY tertiles (low: 2.1%, middle: 1.2%, high: 0.6%). After multivariable adjustment, the high CALLY group had significantly lower 30-day mortality than the low CALLY group (adjusted hazard ratio [HR], 0.40; 95% confidence interval [CI], 0.21–0.75). For long-term mortality, adjusted HRs were 0.60 (95% CI, 0.49–0.72) for the middle CALLY group and 0.50 (95% CI, 0.40–0.62) for the high CALLY group. Restricted mean survival time analyses showed longer adjusted survival in the middle and high CALLY groups compared with the low CALLY group at 10 years (+0.64 and +0.76 years, respectively; both P < 0.001). Restricted cubic spline analysis demonstrated a significant non-linear inverse association between the continuous CALLY index and long-term mortality risk. The CALLY index is a strong and independent predictor of 30-day and long-term all-cause mortality after cardiac surgery. As a simple and readily available biomarker, it may provide valuable incremental prognostic information for perioperative risk stratification.16AFor image description, please refer to the figure legend and surrounding text.16BFor image description, please refer to the figure legend and surrounding text.