According to a recent Systematic Review and Meta-Analysis, the patients with rheumatoid arthritis (RA) exhibited significant serum/plasma levels of osteopontin (OPN) which may become an essential factor to distinguish RA from OA. Before this analysis, the association of osteopontin (OPN) and other proteins, osteocalcin (OCN) and osteoprotegerin (OPG) with RA and OA were not well understood. Therefore, this analysis was conducted to obtain clarity.

The Embase, the Cochrane Library and PubMed were electronically searched to identify literature comparing plasma/serum OCN, OPN and OPG levels. The quality of the study was estimated using the Newcastle-Ottawa Scale. The random-effect model analysis was used to determine the pooled standard mean difference (SMD) with 95% confidence interval (CI) and Q statistic and quantified using I2 for Heterogeneity test determination.

A total of nine studies with 255 OA and 438 RA patients were selected. RA patients exhibited higher serum/plasma OPN levels than OA patients. No difference was noticed for OCN and OPG levels between OA and RA patients. The RA patients and OA patients in Europe and Asian also exhibited no difference in the OPG plasma/serum levels as per subgroup analysis. On the basis of these findings, only OPN plasma/serum levels found to have variations which help to distinguish RA from OA.