Stability across time of the neutrophil-lymphocyte and lymphocyte-neutrophil ratios and associations with outcomes in cardiac surgery patients

BACKGROUND: Elevated white blood cell counts and leukocyte ratios are recognized markers of systemic inflammation associated with poor surgical outcomes. We analyzed the temporal stability and prognostic value of the preoperative Neutrophil-to-Lymphocyte ratio (NLR) and Lymphocyte-to-Neutrophil ratio (LNR) in patients undergoing coronary artery bypass grafts and/or valve surgery. METHODS: We retrospectively reviewed 558 patients who underwent elective cardiac surgery between July 2014 and December 2016, excluding patients with immunosuppressed status. The stability of NLR and LNR was evaluated using interclass correlation coefficients. The patients were dichotomized into two groups, high NLR and low NLR, based on the median value of preoperative NLR in our cohort. A logistic regression model compared preoperative NLR and LNR values to clinical outcomes, including a composite of perioperative events and mid-term mortality. RESULTS: We identified that NLR reliability over time was good (ICC = .592; R-squared = .351), and LNR reliability over time was excellent (ICC = .761; R-squared = .601). Furthermore, an increased duration between collection dates was not significantly correlated with increased variability in NLR (Pearson Correlation Coefficient: −.111, p = .117). On multivariate model, neither high NLR (OR = .879, p = .168) nor low LNR (OR = 3.30, p = .214) was significantly associated with a composite of perioperative events, but increased LNR was associated with lower mid-term mortality (HR .001, p = .026). CONCLUSIONS: Both NLR and LNR were stable over time, up to 100 days, but LNR values were more consistent compared to NLR. High LNR was significantly associated with decreased risk of mid-term mortality, and LNR showed a stronger relationship with mid-term mortality than its NLR counterpart. Both of these findings indicate that LNR may be a more useful and valuable clinical marker.