CRP and rheumatoid arthritis: Non-significant associations were observed in the meta-regression between the effect size and age (t = − 0.86, p = 0.40), sex distribution (t = 1.38, p = 0.19), year of publication (t = 0.78, p = 0.45), sample size (t = − 0.33, p = 0.74), CRP (t = 1.03, p = 0.33), RA duration (t = − 0.10, p = 0.92), or use of methotrexate (t = − 1.62, p = 0.14) and glucocorticoids (t = − 1.05, p = 0.32).