Frisell T, et al. - Researchers sought to investigate the impact of patient characteristics on the selection of biological disease-modifying anti-rheumatic drugs (bDMARDs) in rheumatoid arthritis (RA) in clinical practice. They also intended to quantify the extent to which this would bias direct comparisons of treatment outcome. Findings demonstrated a significant channelling of older and less healthy patients with RA to non-necrosis factor inhibitor (TNFi) bDMARDs, in particular as first bDMARD, although it remained unclear if this channelling represents a maximised benefit/risk ratio. Differences in age, medical history and disease activity need to be accounted for in order to prevent substantial confounding by these in non-randomised comparative studies of available bDMARDs’ safety and effectiveness.