Updated Evidence on Perioperative Neutrophil-to-Lymphocyte Ratio in Cardiac Surgery: A Dual Analysis of Prognostic and Diagnostic Value for Postoperative Atrial Fibrillation.

Background: Post-operative atrial fibrillation (POAF) is a frequent complication after cardiac surgery, increasing morbidity. The neutrophil/lymphocyte ratio (NLR), a simple marker of systemic inflammation, has been studied as a predictor.

Objective: Assess association between NLR and new-onset POAF.

Methods: We systematically searched PubMed, Scopus, Web of Science, and Embase through June 2025 for studies reporting preoperative or postoperative NLR and incidence of POAF in adult cardiac surgery patients. Diagnostic test accuracy (DTA) was assessed to evaluate the predictive performance of preoperative NLR for postoperative atrial fibrillation, using pooled sensitivity, specificity, and likelihood ratios. Subgroup analyses and meta-regression were conducted to explore sources of heterogeneity.

Results: Thirty-two studies (20,056 patients) were included. In 27 studies excluding preoperative AF (13,630 patients), POAF was associated with significantly higher preoperative NLR (SMD = 0.51; 95% CI: 0.34-0.67; p < 0.001; I² = 94.0%). Postoperative NLR was also elevated in POAF patients (SMD = 0.30; 95% CI: 0.13-0.47; p < 0.001; I² = 70.7%). Among four studies including patients with prior AF (6,364 patients), no significant association was observed (SMD = 0.04; p = 0.21). DTA analysis of 12 studies showed pooled sensitivity of 0.52, specificity of 0.71, and diagnostic odds ratio of 3.74 (AUC = 0.713), indicating moderate diagnostic accuracy.

Conclusion: Elevated NLR is associated with increased risk of POAF. Distinguishing new-onset POAF and accounting for surgical type are essential when evaluating NLR as a predictive biomarker.