The neutrophil-to-lymphocyte ratio as a marker of vasculitis activity, severe infection and mortality in anca-associated vasculitis: A retrospective study.

Introduction: Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is a multisystemic disease. Despite the improvement in mortality rate since the introduction of immunosuppression, long-term prognosis is still uncertain not only because of the disease activity but also due to treatment associated adverse effects. The neutrophil-to-lymphocyte ratio (NLR) has been demonstrated as an inflammatory marker in multiple settings. In this study, we aimed to investigate the prognostic ability of the NLR in AAV patients.

Methods: We conducted a retrospective analysis of the clinical records of all adult patients with AVV admitted to the Nephrology and Renal Transplantation Department of Centro Hospitalar Universitário Lisboa Norte from January 2006 to December 2019. NLR was calculated at admission. The outcomes measured were severe infection at 3 months and one-year mortality. The prognostic ability of the NLR was determined using the receiver operating characteristic (ROC) curve. A cut-off value was defined as that with the highest validity. All variables underwent univariate analysis to determine statistically significant factors that may have outcomes. Only variables which significantly differed were used in the multivariate analysis using the logistic regression method.

Results: We registered 45 cases of AVV. The mean age at diagnosis was 67.5±12.1 years and 23 patients were male. The mean Birmingham Vasculitis Activity Score (BVAS) at presentation was 26.0±10.4. Twenty-nine patients were ANCA-MPO positive, 7 ANCA-PR3 positive and 9 were considered negative ANCA vasculitis. At admission, mean serum creatinine (SCr) was 4.9±2.5mg/dL, erythrocyte sedimentation rate (ESR) was 76.9±33.8mm/h, hemoglobin was 9.5±1.7g/dL, C-reactive protein was 13.2±5.8mg/dL and NLR was 8.5±6.8. Thirty-five patients were treated with cyclophosphamide, eight patients with rituximab for induction therapy. Twenty patients developed severe infection within the first three months after starting induction immunosuppression. In a multivariate analysis, older age (73.6±10.5 vs. 62.6±11.3, p=0.002, adjusted OR 1.08 [95% CI 1.01-1.16], p=0.035) and higher NLR (11.9±7.4 vs. 5.9±5.0, p=0.002, adjusted OR 1.14 [95% CI 1.01-1.29], p=0.035) were predictors of severe infection at 3 months. NLR ≥4.04 predicted severe infection at 3 months with a sensitivity of 95% and specificity of 52% and the AUROC curve was 0.0794 (95% CI 0.647-0.900). Nine patients died within the first year. Severe infection at 3 months was independently associated with mortality within the first year (OR 6.19 [95% CI 1.12-34.32], p=0.037).

Conclusions: NLR at diagnosis was an independent predictor of severe infection within the first 3 months after immunosuppression start, and severe infection within the first three months was consequently correlated with one-year mortality. NLR is an easily calculated and low-cost laboratory inflammation biomarker and can prove useful in identifying AAV patients at risk of infection and poorer prognosis.