To study the association between adalimumab serum levels at week 4 and the development of anti‐adalimumab drug antibodies and long‐term outcome in anti‐TNF naive Crohn's disease patients. Serum samples from 116 biologically naive Crohn's disease patients with active disease were prospectively collected at baseline, week 4 and 12. Adalimumab serum levels were measured using the RIDA®QUICK adalimumab lateral flow assay and anti‐adalimumab drug antibodies were determined using a drug‐resistant assay.
