The Prognostic Value of Elevated Perioperative Neutrophil-Lymphocyte Ratio in Predicting Postoperative Atrial Fibrillation After Cardiac Surgery: A Systematic Review and Meta-Analysis

Background: The neutrophil-lymphocyte ratio (NLR) is an emerging inflammatory perioperative biomarker which has been studied to predict the incidence of postoperative atrial fibrillation (POAF) after cardiac surgery. This systematic review and meta-analysis aimed to evaluate the prognostic accuracy of elevated perioperative NLR in predicting POAF after cardiac surgery. Methods: Multiple databases were searched from inception to May 2019 for prognostic studies on perioperative NLR and POAF following cardiac surgery. Maximally adjusted odds ratios (OR) with associated confidence intervals were obtained from each included study and pooled using random effects inverse variance modelling for preoperative NLR measurements, while standardised mean differences were pooled for postoperative NLR values. The significance of inter- and intra-study heterogeneity was explored using meta-regression. Results: 1,799 unique studies satisfied selection criteria, from which 12 studies incorporating 9,262 participants were included. Elevated preoperative NLR significantly predicted POAF, with a pooled OR of 1.42 (95% CI 1.16–1.72). Multiple predefined covariates contributed to inter-study heterogeneity; however, only prevalence of hypertension (p=0.0055), history of congestive cardiac failure (p=0.0282) and average ejection fraction (p=0.0359) were significant effect modifiers. Elevated postoperative NLR was not a significant predictor of POAF (standardised mean difference 1.60 [95% CI -0.56–3.77] between POAF+ and POAF- groups). Conclusions: Elevated preoperative NLR is a promising prognostic biomarker for POAF, but residual sources of heterogeneity remain. Larger scale validation studies are required to justify the integration of preoperative NLR testing into routine clinical practice.