Circulating osteoprotegerin levels are elevated in rheumatoid arthritis: a systematic review and meta-analysis.

This study aimed to systemically review the evidence regarding the relationship between the circulating blood osteoprotegerin (OPG) level and rheumatoid arthritis (RA), as well as the potential influential factors. Research related to plasma/serum OPG levels in RA patients and healthy controls were gathered using PubMed, EMBASE, and The Cochrane Library database (up to Jan. 1, 2017). Pooled standard mean difference (SMD) with 95% confidence interval (CI) was calculated by fixed-effects or random-effect model analysis. Heterogeneity test was performed by the Q statistic and quantified using I 2, and publication bias was evaluated using a funnel plot and Egger's linear regression test. After searching databases, 443 articles were obtained, and 11 studies with 710 RA patients and 561 controls were finally included. Meta-analysis revealed that, compared with the control group, the OPG level was significantly higher in the RA group (P < 0.001), with the SMD of 1.02 and 95%CI (0.20, 1.84). Subgroup analyses showed that race, disease duration, body mass index (BMI), and disease activity score based on the assessment of 28 joints (DAS28) were positively associated with OPG level in RA patients. Our meta-analysis revealed a significantly higher circulating OPG level in RA patients, and it was influenced by race, disease duration, BMI, and DAS28.