Predictive value of systemic immune inflammation index for the inflammatory status and prognosis in patients with anti-neutrophil cytoplasmic antibody associated vasculitis

Abstract

Introduction: The systemic immune-inflammation index (SII) has been explored in a few studies involving patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), yielding conflicting results. Objectives: We aimed to evaluate the role of SII in differentiating and predicting the inflammatory status and prognosis of AAV patients. Materials and methods: This study included 39 AAV patients diagnosed through renal biopsy and 39 age- and sex-matched healthy controls. Patients were divided into subgroups based on ANCA positivity and glomerular filtration rate (GFR) at the time of diagnosis. They were followed up until death, progression to end-stage renal disease (ESRD), or outcome. SII, platelet lymphocyte ratio (PLR), and neutrophil-lymphocyte ratio (NLR) were calculated. Receiver operating characteristic curve (ROC) analysis was used to evaluate the diagnostic value of SII. Spearman's correlation analysis was used to examine the relationship between NLR, PLR, SII, and inflammatory status. Results: All indices were significantly higher in the patient group (p<0.05). Regarding the area under the curve (AUC) values: SII was 0.904 (p=0.001); NLR was 0.940 (p=0.001), and PLR was 0.757 (p=0.001). While ANCA-positive patients had higher levels of SII compared to ANCA-negative patients, we found no difference between the patients with different eGFR levels and among outcome groups. Moreover, Spearman's analysis showed no correlation between SII and C-reactive protein (CRP), CRP/albumin, and the percentage of the crescent. Conclusion: SII and NLR appear to be valuable markers for predicting AAV. Unfortunately, SII failed to demonstrate any correlation with inflammatory status or prognosis. Further prospective studies on this subject will contribute to this area of research.