SOST and rheumatoid arthritis: Among the three studies of serum sclerostin in RA, the heterogeneity was not significant (P = 0.41; I2 = 0), and fixed-effects model was used, and it demonstrated that serum sclerostin levels between RA patients and HC were not significantly different (SMD = −0.10; 95% CI = [−0.34,0.15]; P = 0.43) (Figure 5).