Circulating interleukin-23 levels in ankylosing spondylitis and their correlation with disease activity

Objective: To systematically investigate the relationship between circulating interleukin-23 (IL‑23) levels and ankylosing spondylitis (AS) and establish a correlation between these hematological indices and AS activity/severity. Methods: We searched the Medline, Embase, and Cochrane databases; performed a meta-analysis comparing serum/plasma IL‑23 levels in patients with AS to those of controls; and examined the correlation coefficients between serum/plasma IL‑23 levels and AS activity. Results: Ten studies including 1724 patients with AS and 1589 controls were included in this meta-analysis. This meta-analysis showed that circulating IL‑23 levels were significantly higher in the AS than in the control group (standardized mean difference [SMD] 1.479; 95% confidence interval [CI] 0.308–2.650; p= 0.013). Stratification by ethnicity showed a significantly increased IL‑23 level in the AS group in an Asian population (SMD 1.551; 95% CI 0.543–2.558; p= 0.003). Stratification by adjustment for age and sex revealed significantly higher IL‑23 levels in the AS adjustment group. Subgroup analysis of sample size showed a significantly higher IL‑23 level for a small (n< 150) sample number in the AS group. Meta-analysis of correlation coefficients revealed that the IL‑23 level was positively associated with the Bath Ankylosing Spondylitis Metrology Index (BASMI; correlation coefficient 0.464; 95% CI 0.027–0.752; p= 0.038), erythrocyte sedimentation rate (ESR; correlation coefficient 0.258; 95% CI 0.076–0.422;p= 0.006), and C‑reactive protein (CRP; correlation coefficient 0.291; 95% CI 0.053–0.498;p= 0.017). Conclusion: This meta-analysis demonstrated that the circulating IL‑23 level is significantly higher in patients with AS, and a significant positive correlation exists between the circulating IL‑23 level and BASMI, ESR, and CRP.