The Relationship Between Systemic Immune Inflammation Index and Disease Activity in Ankylosing Spondylitis Patients

Aim: This study aimed to investigate the relationship between the systemic immune inflammation index (SII), platelet-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio (NLR), and disease activity and functional status in patients with ankylosing spondylitis (AS). Method: This cross-sectional clinical study included a total of 90 patients diagnosed with AS according to the Modified New York Criteria, aged between 18 and 65, who presented to our outpatient clinics. Demographic data and laboratory parameters, including platelet, neutrophil, basophil, eosinophil, and lymphocyte counts, mean platelet volume (MPV), red blood cell distribution width (RDW), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR), were recorded. NLR, PLR and SII values were calculated. Results: The mean age of the AS patients included in the study was 42.9±11.3 years. Positive correlations were observed between SII and CRP (p=0.010, r=0.269) and ESR (p=0.007, r=0.282). No significant correlations were found between SII and BASDAI, BASFI, or BASMI (p>0.05). NLR and PLR values didn't differ significantly between active and inactive disease groups (p>0.05). There was a significant correlation between SII and Ankylosing Spondylitis Disease Activity Score with erythrocyte sedimentation rate (ASDAS-ESR) (rho=0.282, p=0.007). Conclusion: The study suggests that SII correlates positively with CRP and ESR, common inflammatory markers in AS. SII could be a potential marker for assessing inflammation, especially in patients with higher disease activity.