Serum Levels of Copper and Zinc in Patients with Rheumatoid Arthritis: a Meta-analysis

Many publications with conflicting results have evaluated serum levels of copper (Cu) and zinc (Zn) in patients with rheumatoid arthritis (RA). To derive a more precise estimation of the relationship, a meta-analysis was conducted. Relevant published data were retrieved through PubMed, Chinese National Knowledge Infrastructure (CNKI), and Chinese Biomedical Database (CBM) before September 20, 2014. Weighted mean difference (WMD) with a 95 % confidence interval (95 % CI) was calculated using STATA 11.0. A total of 26 studies, including 1444 RA cases and 1241 healthy controls, were collected in this meta-analysis. Pooled analysis found that patients with RA had a higher serum level of Cu and a lower serum Zn level than the healthy controls (Cu (μg/dl), WMD = 31.824, 95 % CI = 20.334, 43.314; Zn (μg/dl), WMD = -12.683, 95 % CI = -19.783, -5.584). Subgroup analysis showed that ethnicity had influence on the serum level of Cu (μg/dl) (Caucasian, WMD = 43.907, 95 % CI = 35.090, 52.723, P < 0.001; Asian, WMD = 14.545, 95 % CI = -12.365, 41.455, P = 0.289) and Zn (μg/dl) (Caucasian, WMD = -11.038, 95 % CI = -23.420, 1.344, P = 0.081; Asian, WMD = -14.179, 95 % CI = -18.963, -9.394, P < 0.001) in RA and healthy controls. No evidence of publication bias was observed. This meta-analysis suggests that increased serum level of Cu and decreased serum level of Zn are generally present in RA patients.