Association between baseline systemic immune-inflammation index and subsequent stroke in ANCA-associated vasculitis

The systemic immune-inflammation index (SII) is reportedly an effective predictor of poor outcomes in malignancies and inflammatory diseases. Therefore, this study investigated the association between baseline SII and subsequent stroke in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV).

We selected 339 immunosuppressive drug-naïve patients newly diagnosed with AAV from an observational AAV cohort and retrospectively reviewed their medical records. The baseline Birmingham Vasculitis Activity Score (BVAS) was reviewed, and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels were recorded. Baseline SII was calculated thus: SII = neutrophil count × platelet count/lymphocyte count. Subsequent stroke was defined as ischaemic or haemorrhagic stroke that occurred after diagnosis.

The 339 AAV patients had a median age of 61.0 years; the majority were women. The median baseline BVAS and SII were 12.0 and 1229.9, respectively. Of the 339 patients, 20 (5.9%) experienced a subsequent stroke. Baseline SII was significantly correlated with ESR (r = 0.361) and CRP levels (r = 0.485). Baseline SII (standardised β 0.117) was independently correlated with BVAS, as seen on multivariable linear regression analysis. Baseline SII showed modest discrimination for subsequent stroke (AUC 0.662, 95% CI 0.532-0.793), and a cohort-derived cutoff of 2390.5 was identified. Patients with baseline SII ≥ 2390.5 and those in the upper half of baseline SII showed significantly lower cumulative stroke-free survival rates. However, baseline SII was not independently associated with subsequent stroke in the primary multivariable Cox analyses.

To the best of our knowledge, this is the first study to demonstrate an association between baseline SII and subsequent stroke in patients with AAV. Further studies are required to establish its independent and incremental prognostic value. Key Points • Baseline SII was significantly correlated with cross-sectional BVAS, ESR, and CRP levels. • Individuals with baseline SII ≥ 2390.5 and those with the upper half of baseline SII showed significantly reduced cumulative stroke-free survival rates compared to those without. • Higher baseline SII was associated with subsequent stroke in patients with AAV; however, its independent and incremental prognostic value remains to be established.