title: Predicting Endoscopic Disease Activity in Crohn's Disease: A New and Validated Noninvasive Disease Activity Index (The Utrecht Activity Index).
abstract: BACKGROUND
  Mucosal healing is presently considered one of the primary goals in treatment of Crohn's disease (CD), but this can only be confirmed by endoscopy. We aimed to design and validate a new disease activity index based on a combination of clinical characteristics and readily available laboratory parameters, which reliably predicts the presence and severity of endoscopic disease activity in patients with CD.
  
  
  METHODS
  Thirteen clinical characteristics and laboratory variables were selected for analysis. Endoscopic disease activity was assessed by the Crohn's disease Endoscopic Index of Severity. A linear regression model was based on 93 ileocolonoscopies performed in 82 patients with CD and internally validated by bootstrap resampling. Subsequently, the newly developed model was validated in a cohort of 99 patients.
  
  
  RESULTS
  The number of liquid stools during 1 day × 0.25 + C-reactive protein (in milligrams per liter) × 0.1 + platelet count (× 10(9)/L) × 0.01 + fecal calprotectin (in milligrams per liter) × 0.001 - mean platelet volume (in femtoliters) × 0.2 optimally predicted the severity of endoscopic disease activity (bootstrap adjusted R2 = 0.50). The model demonstrated good agreement in the external validation (r = 0.7), especially for (ileo)colonic CD (r = 0.8). Using receiver operator characteristic statistics, a cutoff point of 3 on the new index indicated endoscopic disease activity with a sensitivity of 80% and a specificity of 92%.
  
  
  CONCLUSIONS
  This newly developed, noninvasive, index was found to reliably predict endoscopic disease activity in patients with CD. This tool can facilitate clinical decision making and might prove valuable in clinical trials.
authors.affiliation: *Department of Internal Medicine and Gastroenterology, Tergooi Hospital, Hilversum, the Netherlands; †Center for Medical Decision Making, Department of Public Health, Erasmus Medical Center Rotterdam, Rotterdam, the Netherlands; ‡Department of Gastroenterology, VU Medical Center, Amsterdam, the Netherlands; §Department of Gastroenterology, Erasmus Medical Center Rotterdam, Rotterdam, the Netherlands; ‖Center for Inflammatory Bowel Diseases, UCLA Health System, Los Angeles, California; ¶Department of Gastroenterology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands; **Department of Gastroenterology, University Medical Center Utrecht, Utrecht, the Netherlands; and ††Department of Gastroenterology, Meander Medical Center, Amersfoort, the Netherlands.
authors.forename: Itta M
authors.initials: IM
authors.lastname: Minderhoud
authors.forename: Ewout W
authors.initials: EW
authors.lastname: Steyerberg
authors.forename: Ad A
authors.initials: AA
authors.lastname: van Bodegraven
authors.forename: C Janneke
authors.initials: CJ
authors.lastname: van der Woude
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Hommes
authors.forename: Gerard
authors.initials: G
authors.lastname: Dijkstra
authors.forename: Herma H
authors.initials: HH
authors.lastname: Fidder
authors.forename: Matthijs P
authors.initials: MP
authors.lastname: Schwartz
authors.forename: Bas
authors.initials: B
authors.lastname: Oldenburg
mesh_terms: D000328:Adult; D002097:C-Reactive Protein / Q000032:analysis; D003106:Colon / Q000473:pathology; D003113:Colonoscopy / Q000706:statistics & numerical data; D003424:Crohn Disease / Q000097:blood / Q000473:pathology*; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D007082:Ileum / Q000473:pathology; D039841:Leukocyte L1 Antigen Complex / Q000032:analysis; D016014:Linear Models; D008297:Male; D010976:Platelet Count; D011237:Predictive Value of Tests; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D039841:Leukocyte L1 Antigen Complex; D002097:C-Reactive Protein