Serum DKK-1 level in the development of ankylosing spondylitis and rheumatic arthritis: a meta-analysis

To explore the association of serum Dickkopf-1 (DKK-1) levels with the development of ankylosing spondylitis (AS) and rheumatic arthritis (RA) in humans, databases including PubMed, EBSCO, Springerlink, Ovid, WANFANG and China National Knowledge Infrastructure (CNKI) were searched to identify relevant studies. On the basis of rigorous inclusion and exclusion criteria, case-control studies of the relationships between serum DKK-1 levels and AS and RA published before December 2014 were enrolled. Statistical analyses were performed using Comprehensive Meta-analysis 2.0 (CMA 2.0). Seven case-control trials with a total of 300 AS patients, 136 RA patients and 232 healthy controls were included in this study. Meta-analysis results revealed that DKK-1 serum levels were significantly higher in AS patients than in normal controls (standard mean differences (s.m.d.)=0.301, 95% confidence interval (CI)=0.094-0.507, P=0.004), whereas no significant difference in DKK-1 serum levels was observed between RA patients and healthy controls (s.m.d.=0.798, 95% CI=-2.166-3.763, P=0.598). Serum DKK-1 level may be closely related to the development of AS but not of RA.