Objective To identify predictors of response to tumor necrosis factor (TNF) antagonists in ankylosing spondylitis (AS) and psoriatic arthritis (PsA).

Methods Systematic review and meta-analysis of clinical trials and observational studies based on a systematic search. Meta-analyses of similar observations were performed using random effects computing summary OR. Heterogeneity was tested using I², and risks of bias using funnel plots and the Egger test. Meta-regression was used to explore causes of heterogeneity.

Results The electronic search captured 1340 references and 217 abstracts. 17 additional articles were identified after searching by hand. A total of 59 articles meet the purpose of the study and were reviewed. 37 articles (33 studies) included 6736 patients with AS and 23 articles (22 studies) included 4034 patients with PsA. 1 article included data on AS and PsA. Age (OR (95% CI) 0.91 (0.84 to 0.99), I²=84.1%), gender (1.57 (1.10 to 2.25), I²=0.0%), baseline BASDAI (1.31 (1.09 to 1.57), I²=0.0%), baseline BASFI (0.86 (0.79 to 0.93), I²=24.9%), baseline dichotomous C reactive protein (CRP) (2.14 (1.71 to 2.68), I²=22.3%) and human leucocyte antigen B27 (HLA-B27) (1.81 (1.35 to 2.42), I²=0.0%) predict BASDAI50 response in AS. No factor was identified as a source of heterogeneity. Only meta-analysis of baseline BASFI showed risk of publication bias (Egger test, p=0.004). Similar results were found for ASAS criteria response. No predictors of response were identified in PsA.

Conclusions Young age, male sex, high baseline BASDAI, low baseline BASFI, high baseline CRP and HLA-B27 predict better response to TNF antagonists in AS but not in PsA.