Pre-operative Neutrophil to Lymphocyte Ratio is Associated With 30 Day Death or Amputation After Revascularisation for Acute Limb Ischaemia

Abstract

Objective: Inflammation is an early feature of acute limb ischaemia (ALI), hence the potential prognostic significance of inflammatory biomarkers. This study aimed to assess the value of pre-operative inflammatory biomarkers, specifically the neutrophil to lymphocyte ratio (NLR) and the platelet to lymphocyte ratio (PLR), for predicting an adverse outcome after revascularisation for ALI.

Methods: All patients submitted to lower limb revascularisation for Rutherford IIa or IIb ALI at the authors' institution between 2009 and 2019 were screened retrospectively. Pre-operative NLR and PLR were analysed, along with other known prognostic factors. Primary outcome was the composite endpoint of 30 day death or amputation.

Results: A total of 345 patients were included, 84 of whom suffered the primary outcome (24.3%). The median follow up was 23.1 months (3.1 - 52.2). Higher age (OR 1.05 per year increase, 95% CI 1.01 - 1.09), diabetes (OR 2.63, 95% CI 1.14 - 6.06), Rutherford grade IIb vs. IIa (OR 5.51, 95% CI 2.11 - 14.42), higher NLR (OR 1.28 per unit increase, 95% CI 1.12 - 1.47), and fasciotomy need (OR 3.44, 95% CI 1.14 - 10.34) were independently associated with 30 day death or amputation, whereas pre-operative statin or anticoagulant medication were associated with a risk reduction (OR 0.23, 95% CI 0.53 - 0.96 and OR 0.20, 95% CI 0.05 - 0.84, respectively). PLR did not show an independent effect on this population. Pre-operative NLR presented a good discriminative ability (AUC 0.86, 95% CI 0.82 - 0.90). A cut off NLR level ≥ 5.4 demonstrated a 90.5% sensitivity and 73.6% specificity for 30 day death or amputation. Kaplan-Meier analysis showed that patients with pre-operative NLR ≥ 5.4 had significantly lower 30 day, six month and one year amputation free survival when compared with those with NLR < 5.4 (64.8 ± 4.0%, 44.1 ± 4.1%, and 37.5 ± 4.1% vs. 98.5 ± 0.9%, 91.9 ± 2.0%, and 85.9 ± 2.5%, log rank p < .001).

Conclusion: In this study, higher pre-operative NLR was associated with 30 day death or amputation following intervention for Rutherford grade IIa or IIb ALI. NLR potentially stands as a simple, widely available and inexpensive biomarker that can refine decision making and possibly contribute to ALI morbidity and mortality reduction.

Keywords: Acute limb ischaemia; Amputation; Biomarkers; Mortality; Neutrophil-lymphocyte ratio; Prognosis.