Moreover, significant RD-associated elevations in periostin concentrations were observed in studies of patients with systemic sclerosis (SMD = 1.13, 95% CI 0.48 to 1.78, p = 0.001; I2 = 89.6%, p < 0.001) and rheumatoid arthritis (SMD = 1.26, 95% CI 0.36 to 2.16, p = 0.006; I2 = 87.9%, p < 0.001) whereas no significant between-group differences were observed in studies of patients with osteoarthritis (SMD = −0.01, 95% CI −0.38 to 0.36, p = 0.96; I2 = 0.0%, p = 0.70), with a virtually absent heterogeneity observed in the last subgroup. The gene discussed is POSTN; the disease is systemic sclerosis.