Elevated circulating asymmetric dimethylarginine levels in rheumatoid arthritis: a systematic review and meta-analysis.

Rheumatoid arthritis (RA) patients have increased risk of cardiovascular disease (CVD) death. Elevated asymmetric dimethylarginine (ADMA) levels have been reported to be an independent predictor of CVD morbidity and mortality, however, the role of ADMA in RA remains undetermined. To derive a more accurate estimation on circulating ADMA levels in RA patients, a meta-analysis was performed. Embase, PubMed, and The Cochrane Library database (up to October 7 2018) were used to acquire published literatures. Heterogeneity test was performed by the Q statistic and quantified using I. Publication bias was evaluated using a funnel plot and Egger's linear regression test. A total of 174 articles were identified, 16 studies with 1365 subjects (666 RA patients and 699 healthy individuals) were ultimately included. Plasma/serum ADMA levels appeared to be higher in RA patients than healthy controls (SMD = 0.84, 95% CI 0.32, 1.35). By assessing the BMI, age, disease duration and disease activity as subgroups, BMI ≥ 24 and BMI < 24 groups both showed elevated ADMA levels than controls, disease duration ≥ 8, age < 50 and disease activity ≥ 3.2 and < 5.1 group had a higher ADMA level than control groups. However, disease duration < 8, disease activity ≥ 5.1 and age ≥ 50 groups showed no difference between two groups. Circulating ADMA levels are higher in RA patients compared with healthy controls. In addition, ADMA levels are influenced by age, disease duration and disease activity.