The neutrophil-to-lymphocyte ratio is associated with adverse outcomes in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis

Background The neutrophil-to-lymphocyte ratio (NLR) is a convenient biomarker reflecting systemic inflammation and immune balance. While its prognostic value is established in other diseases, its role in predicting long-term outcomes in patients with ANCA-associated vasculitis (AAV) remains unclear. This study aimed to investigate the association between NLR and organ involvement, all-cause mortality, and end-stage renal disease (ESRD) in AAV patients. Methods We conducted a retrospective study of 532 patients first diagnosed with AAV at Tianjin Medical University General Hospital between June 2012 and June 2024. The primary outcome was all-cause mortality, and the secondary outcome was ESRD. Logistic regression was used to assess associations between NLR and organ involvement. Restricted cubic spline (RCS), Cox proportional hazards regression, Kaplan-Meier survival analysis, time-dependent receiver operating characteristic (ROC) and subgroup analysis were employed to analyze the association between NLR and outcomes in AAV patients. Results At baseline, patients with higher NLR level exhibited more severe inflammation, worse renal function, and higher disease activity (all P < 0.05). After adjustment for age and sex, NLR was independently associated with the presence of fever (adjusted OR 1.03, 95% CI 1.00–1.06, P = 0.042) and renal dysfunction (adjusted OR 1.04, 95% CI 1.01–1.07, P = 0.021) at diagnosis. RCS analysis revealed a nonlinear relationship between NLR and all-cause mortality, with a threshold of 10. After multivariable adjustment, patients in the high NLR group (NLR > 10) had a 77% increased risk of mortality compared to those in the low NLR group (adjusted HR 1.77, 95% CI 1.17–2.68, P = 0.007). NLR was not significantly associated with the risk of ESRD (adjusted HR 1.26, 95% CI 0.73–2.18, P = 0.400). The difference in the proportion of infection-related mortality between the high and low NLR groups was not statistically significant (60.0% vs 50.4%, P > 0.05). Conclusion A nonlinear relationship with a saturation effect was observed between NLR and all-cause mortality in AAV patients. An elevated NLR served as an independent risk factor for adverse outcomes. This simple biomarker could be valuable for risk stratification in AAV patients.