title: Therapeutic drug monitoring of infliximab in inflammatory bowel disease patients in a teaching hospital setting: results of a prospective cohort study.
abstract: OBJECTIVE
  Therapeutic drug monitoring (TDM) of infliximab (IFX) is not routinely implemented in our clinical practice. We therefore carried out a prospective cohort study measuring IFX trough levels in our total inflammatory bowel disease (IBD) population in relation to remission.
  
  
  METHODS
  Patient demographics, and medication and clinical history were collected from the electronic hospital information system. Blood was drawn at one time point for the determination of IFX trough levels and antibodies to IFX (ATI). Disease activity indices [Crohn's disease activity index (CDAI) and the Truelove-Witts disease activity index (TWDAI) for Crohn's disease and ulcerative colitis, respectively] and quality-of-life scores (Visual Analog Scale) were obtained.
  
  
  RESULTS
  We included 107 patients. IFX levels varied from less than 0.02 to 21.9 μg/ml. The median IFX level was 2.8 μg/ml [interquartile range (IQR) 1.37-5.13]. The IFX level was associated significantly with remission (P=0.007). The median IFX level was 3.9 μg/ml (IQR 1.9-6.53) in patients in remission and 2.1 μg/ml in patients with active disease (IQR 0.77-4.38) (P=0.074). Receiver operating charecteristic curve analysis indicated a cutoff value of 2.18 μg/ml for CD and 6.26 μg/ml for UC. Eleven patients (10.3%) had developed ATI. The appearance of ATI was associated with the disappearance of IFX [relative risk: 2.2 (95% confidence interval: 1.368-3.610) P<0.0001], but not with relapse. The presence of ATI induced more infusion reactions [relative risk: 11.7 (95% confidence interval: 2.74-49.60) P<0.001].
  
  
  CONCLUSIONS
  TDM of IFX in IBD outpatients in a teaching hospital setting showed large interindividual differences in IFX trough levels. Despite this, we still found a significant association between remission and IFX trough levels. We determined cutoff values for both IBD modalities. IFX trough levels were not detectable in a significant proportion of IBD patients; TDM is indicated to identify this group of patients.
authors.affiliation: Departments of aClinical Pharmacy bGastroenterology & Hepatology, Máxima Medical Center, Veldhoven, The Netherlands.
authors.forename: Andrea
authors.initials: A
authors.lastname: Warman
authors.forename: Jan Willem A
authors.initials: JW
authors.lastname: Straathof
authors.forename: Luc J J
authors.initials: LJ
authors.lastname: Derijks
mesh_terms: D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood* / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000097:blood* / Q000627:therapeutic use; D003093:Colitis, Ulcerative / Q000097:blood / Q000188:drug therapy; D003424:Crohn Disease / Q000097:blood / Q000188:drug therapy; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D005765:Gastrointestinal Agents / Q000097:blood / Q000627:therapeutic use; D006784:Hospitals, Teaching; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000097:blood* / Q000188:drug therapy; D000069285:Infliximab; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012074:Remission Induction; D012720:Severity of Illness Index
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000911:Antibodies, Monoclonal; D005765:Gastrointestinal Agents; D000069285:Infliximab