CRP and rheumatoid arthritis: In meta-regression, there were non-significant associations between the effect size and age (t = 0.50, p = 0.62), sex distribution (t = − 0.81, p = 0.43), publication year (t = − 0.81, p = 0.43), number of participants (t = − 1.29, p = 0.21), CRP (t = 1.41, p = 0.19), ESR (t = 1.08, p = 0.31), RA duration (t = − 1.20, p = 0.25), or use of methotrexate (t = − 0.96, p = 0.36), and DMARDs (t = − 0.49, p = 0.63).