Immunogenicity of adalimumab could impair important treatment outcome parameters in patients with rheumatoid arthritis (RA). Patients who developed antiadalimumab antibodies (AAA) during a 3 year time period achieved less often minimal disease activity or remission and treatment failure occurred more often compared with patients without AAA.1 There were remarkable baseline differences: patients developing AAA had more long-standing, severe disease and less often used concomitant medication including lower doses of methotrexate (MTX), compared with patients not developing AAA. In literature, a favourable effect of concomitant MTX use on the immunogenicity of adalimumab for several inflammatory conditions is suggested.2

To investigate which MTX dose is sufficient to reduce immunogenicity, patients of …