Association between C‐reactive protein gene variant and treatment efficacy of etanercept in ankylosing spondylitis patients receiving hip arthroplasty

BACKGROUND: C‐reactive protein (CRP) level is one of the most widely used parameters to assess ankylosing spondylitis (AS), since CRP is associated with poor radiographic progression of AS patients. Recent studies have investigated the association between CRP gene variants and AS risk, but with conflicting findings. MATERIAL AND METHODS: We enrolled 232 AS cases and 314 controls in this case‐control study. Next, we assessed the association of CRP gene rs3091244 polymorphism with the efficacy of etanercept for AS. Genotyping was done using a custom‐by‐design 48‐Plex SNP scanTM Kit. RESULTS: CRP gene rs3091244 polymorphism was associated with an increased risk of AS in this Chinese population. Clinical indicators of AS patients including morning stiffness time, Bath AS function index (BASFI), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Visual Analogue Scale (VAS), erythrocyte sedimentation rate (ESR), and CRP were significantly decreased after 12 weeks of etanercept treatment. Furthermore, AA genotype carriers showed higher values of VAS, BASDAI, BASFI, and CRP before etanercept treatment. AA genotype or A allele of rs3091244 polymorphism was associated with Ankylosing Spondylitis Assessment Study group response criteria 20 scores (ASAS20) and Assessment in SpondyloArthritis international Society 40 response (ASAS40) improvement. In addition, AA genotype carriers showed significantly higher CRP levels compared with genotype GG carriers (16.3 vs 8.8 mg/L). CONCLUSION: CRP gene rs3091244 polymorphism is associated with an increased risk of AS. Additionally, rs3091244 polymorphism could serve as a biomarker for good response to etanercept treatment in AS.