Prognostic value of alkaline phosphatase-to-albumin ratio in critically ill patients with atrial fibrillation: A MIMIC-IV retrospective study

OBJECTIVE: Atrial fibrillation (AF) is a prevalent arrhythmia associated with elevated risks of cardiovascular events and all-cause mortality. Identifying reliable prognostic biomarkers is essential for outcome assessment in AF patients. The alkaline phosphatase-to-albumin ratio (APAR), which integrates inflammation, vascular calcification, and nutritional status, has shown independent prognostic value in various conditions, yet its role in AF remains underexplored. METHODS: This retrospective cohort study utilized the MIMIC-IV database and included 676 adult (≥18 years) AF patients. Participants were divided into two groups based on their APAR threshold inflection point: APAR <4 and APAR ≥4. Restricted cubic spline (RCS) regression and Cox proportional hazards models assessed the association between APAR and mortality at 60, 365, and 1460 days. Predictive performance was evaluated using the receiver operating characteristic (ROC) curve and the corresponding area under the curve (AUC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI). RESULTS: RCS analysis revealed a nonlinear association between APAR and mortality in AF patients. The receiver operating characteristic (ROC) curve shows that it has some predictive value, with AUC values of 0.6331 (60 days), 0.6477 (365 days), and 0.6424 (1460 days). Kaplan-Meier survival curves showed that the survival rate of the APAR ≥ 4 group was significantly lower than that of the APAR < 4 group at all three time points. Cox regression confirmed APAR as an independent predictor of mid-to long-term mortality, with sustained prognostic significance at 365-day and 1460-day follow-up. CONCLUSION: In conclusion, APAR represents an easily obtainable independent prognostic biomarker for mid- to long-term mortality in critically ill patients with AF, displaying a nonlinear association with mortality. These findings suggest the potential clinical utility of APAR in guiding patient management.