Subtherapeutic concentrations of infliximab and adalimumab are associated with increased disease activity in Crohn’s disease:

Background:Low anti-tumor necrosis factor α (TNFα) serum concentrations may result in lack of treatment response in patients with inflammatory bowel disease. We determined the anti-TNFα drug concentrations in patients with inflammatory bowel disease and investigated whether or not subtherapeutic drug concentrations were associated with increased levels of disease activity.Methods:In a single-center cross-sectional study, we included patients with ulcerative colitis or Crohn’s disease who were receiving infliximab or adalimumab maintenance therapy. Demographic data, disease activity symptom scores (Partial Mayo Score, Harvey Bradshaw Index), inflammatory markers [C-reactive protein (CRP), fecal calprotectin], antidrug antibodies and serum drug concentrations were recorded. Therapeutic drug concentrations were defined as 3–8 mg/liter for infliximab and 5–12 mg/liter for adalimumab.Results:Of 210 patients included, 137 (65.2%) had Crohn’s disease. In the adalimumab group, subtherapeutic drug concentrations w...