title: C-reactive protein is an indicator of serum infliximab level in predicting loss of response in patients with Crohn's disease.
abstract: BACKGROUND
  The ability of serum infliximab level to predict clinical outcome in infliximab therapy in Crohn's disease is unclear. Here, we aimed to clarify the correlation between the timing of loss of response (LOR) to treatment and a decrease in serum infliximab level, and, in addition, to identify an indicator of infliximab level.
  
  
  METHODS
  The study used data from a previous clinical study of infliximab for Crohn's disease, in which infliximab was initially given at 0, 2, 6 weeks at 5 mg/kg, and then at 8-week intervals to 62 week-10 responders. Of these 62, here we analysed data from 57 in whom Crohn's disease activity index and serum infliximab level were evaluated at week 14.
  
  
  RESULTS
  Twelve patients showed a clinical response despite an infliximab level <1 μg/mL at week 14; of these, 8 (67 %) experienced LOR by week 54. A decrease in infliximab level preceded LOR in 6 (75 %). In receiver operating characteristic curve analysis, C-reactive protein (CRP) showed better performance in detecting an infliximab level <1 μg/mL. Infliximab level was <1 μg/mL in 60-80 % of patients with CRP >0.5 mg/dL. Time to LOR (median: 22.0 weeks) was significantly longer than that to a decrease in infliximab level to <1 μg/mL (14.0 weeks, p < 0.05) or to an increase in CRP to >0.5 mg/dL (14.0 weeks, p < 0.01).
  
  
  CONCLUSIONS
  A decrease in serum infliximab level preceded LOR, and was easily detected by an increase in CRP. The CRP may be an indicator of serum infliximab level in predicting LOR.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan, thibi@z5.keio.jp.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Hibi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sakuraba
authors.forename: Mamoru
authors.initials: M
authors.lastname: Watanabe
authors.forename: Satoshi
authors.initials: S
authors.lastname: Motoya
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ito
authors.forename: Noriko
authors.initials: N
authors.lastname: Sato
authors.forename: Toru
authors.initials: T
authors.lastname: Yoshinari
authors.forename: Kenta
authors.initials: K
authors.lastname: Motegi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kinouchi
authors.forename: Masakazu
authors.initials: M
authors.lastname: Takazoe
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kawakami
authors.forename: Takayuki
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hirata
authors.forename: Shinji
authors.initials: S
authors.lastname: Tanaka
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Ashida
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Matsui
mesh_terms: D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood* / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000097:blood* / Q000627:therapeutic use; D019540:Area Under Curve; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D003424:Crohn Disease / Q000097:blood* / Q000188:drug therapy*; D004351:Drug Resistance; D005260:Female; D006801:Humans; D000069285:Infliximab; D008297:Male; D011237:Predictive Value of Tests; D012372:ROC Curve; D012720:Severity of Illness Index; D013997:Time Factors; D055815:Young Adult
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000911:Antibodies, Monoclonal; D015415:Biomarkers; D002097:C-Reactive Protein; D000069285:Infliximab