Elevated Neutrophil-Lymphocyte Ratio Predicts Mortality After Elective Endovascular Aneurysm Repair

Abstract

The neutrophil-lymphocyte ratio (NLR), computed by dividing the absolute neutrophil count by absolute lymphocyte count, is an inexpensive inflammatory marker that incorporates the balance of the innate (neutrophil) and adaptive (lymphocyte) immune responses. The objective of this study was to determine whether preoperative NLR is associated with mortality after elective endovascular aneurysm repair (EVAR). A retrospective review of patients who underwent elective EVAR between 2010 and 2017 and had a preoperative complete blood count with differential within 30 days of repair was conducted. A receiver operating characteristic curve was used to determine the optimal cutoff value of NLR most predictive of mortality. NLR was therefore dichotomized so that patients above the threshold were at increased risk of mortality compared with those below it. Continuous variables were analyzed using Wilcoxon nonparametric signed rank test and categorical variables with the Fisher exact test. Kaplan-Meier survival analysis was used to compare NLR and mortality. Overall, 108 patients were included. An NLR of ≥4.0 was found to be predictive of mortality (P < .0001); 32 patients composed the high NLR (≥4.0) group, and the remaining 76 patients formed the low NLR (<4.0) group. Baseline characteristics were similar between groups, except that the high NLR group was older. At a mean of 36.4 months of follow-up, the overall mortality rate was 34.3%. Perioperative mortality was similar between groups. However, mortality rates were significantly greater in the high NLR group at 1 year (28.1% vs 3.9%; P = .0008), 2 years (43.8% vs 9.2%; P < .0001), and 5 years (71.9% vs 15.8%; P < .0001; Fig). The mean preoperative NLR of the deceased was higher (5.94 ± 5.20) than the NLR of those who survived (2.87 ± 1.61; P < .0001). Secondary interventions and sac enlargement rates were similar between groups. Patients with an elevated preoperative NLR, irrespective of other comorbidities, may represent a previously unrecognized subset of patients at heightened risk of mortality after elective EVAR. A complete blood count with differential is an inexpensive test that may be used as a prognostic indicator for outcome after EVAR. Further research is warranted to identify clinical, pathologic, and anatomic factors associated with elevated NLR and to determine the modifiable factors of it, which may help improve survival.