Systemic immune-inflammation index could estimate the cross-sectional high activity and the poor outcomes in immunosuppressive drug-naive patients with antineutrophil cytoplasmic antibody-associated vasculitis

Objectives We investigated whether systemic immune-inflammation index (SII) at diagnosis can estimate the cross-sectional high activity and predict the poor outcomes in immunosuppressive drug-naive patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Methods We retrospectively reviewed the medical records of 163 patients with AAV and obtained clinical and laboratory data. We calculated Birmingham vasculitis activity score (BVAS) as well as five-factor score (FFS) (2009) at diagnosis. SII at diagnosis was calculated by the equation of (SII at diagnosis = platelet count x neutrophil count/lymphocyte count at diagnosis). Severe AAV was defined as BVAS at diagnosis >= 16. The odds ratio was assessed using the multivariable logistic regression analysis and cumulative survival rates were compared by the Kaplan-Meier survival analysis. Results The median age at diagnosis was 58.0 years old and 51 patients were men. The median BVAS was 12.0. Fifty-seven patients had severe AAV. The median SII at diagnosis was 1349.6. In the multivariable analysis, only SII exhibited a significant odds ratio for the cross-sectional severe AAV (P = 0.043). We obtained the cut-off of SII at diagnosis for severe AAV as 1573.56. Patients with SII at diagnosis >= 1573.56 exhibited a significantly high relative risk of the cross-sectional severe AAV compared to those without (relative risk 4.625). Furthermore, patients with SII at diagnosis >= 1573.56 exhibited significantly the lower cumulative relapse free and renal survivals than those without. Conclusion Systemic immune-inflammation index at diagnosis could estimate the cross-section severe AAV and predict the poor outcomes in AAV patients.