Perioperative Neutrophil-Lymphocyte Ratio Predicts Mortality After Cardiac Surgery: Systematic Review and Meta-Analysis

Objectives: Neutrophil-lymphocyte ratio (NLR) is an inflammatory biomarker that has been evaluated across a variety of surgical disciplines and is widely predictive of poor postoperative outcome, but its value in cardiac surgery is unclear. The authors did this systematic review and meta-analysis to determine the impact of elevated perioperative NLR on survival after cardiac surgery. Design: Systematic review and meta-analysis of study-level data. Setting: Multiple hospitals involved in an international pool of studies. Participants: Adults undergoing cardiac surgery. Interventions: None. Measurements and Main Results: The authors searched multiple databases from inception until November 2020. They generated summary hazard ratios (HR) and odds ratios (OR) for the association of elevated preoperative NLR with long-term and short-term mortality following cardiac surgery. They separately reported on elevated postoperative NLR. Between-study heterogeneity was explored using metaregression. The authors included 12 studies involving 13,262 patients undergoing cardiac surgery. Elevated preoperative NLR was associated with worse long-term (>30 days) (hazard ratio [HR] 1.56; 95% CI [confidence interval], 1.18-2.06; 8 studies) and short-term (<30 days) mortality (OR 3.18; 95% CI, 1.90-5.30; 7 studies). One study reported the association of elevated postoperative NLR with long-term mortality (HR 8.58; 95% CI, 2.55-28.85). There was considerable between-study heterogeneity for the analysis of long-term mortality (I² statistic 94.39%), which mostly was explained by study-level variables, such as the number of variables adjusted for by included studies and how many of these significantly increased the risk of long-term mortality, high risk of bias, and number of study centers, as well as participant level factors, such as average participant age and hypertension prevalence. Conclusions: Perioperative NLR is an independent predictor of short-term and long-term postoperative mortality following cardiac surgery. Further research is required to determine which patient-level factors modify the prognostic value of NLR and to evaluate its role in routine clinical practice.