title: Assessment of reliability and validity of IBD phenotyping within the National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) IBD Genetics Consortium (IBDGC).
abstract: BACKGROUND
  The NIDDK IBD Genetics Consortium (IBDGC) collects DNA and phenotypic data from inflammatory bowel disease (IBD) subjects to provide a resource for genetic studies. No previous studies have been performed on the reliability and validity of phenotypic determinations in either Crohn's disease (CD) or ulcerative colitis (UC) using primary records. Our aim was to determine the reliability and validity of these phenotypic assessments.
  
  
  METHODS
  The de-identified records of 30 IBD patients were reviewed by 2 phenotypers per center using a standard protocol for phenotypic assessment. Each phenotyper evaluated 10 charts on 2 occasions 5 months apart. Reliability was expressed as the kappa (kappa) statistic. Performance characteristics were determined by comparison to a consensus-derived "gold standard" and by generation of receiver operating characteristic (ROC) curves.
  
  
  RESULTS
  Agreement for diagnosis was excellent (kappa = 0.82; 95% confidence interval [CI]: 0.71-0.92). Agreement for CD location was good for jejunal, ileal, colorectal, and perianal disease with kappa between 0.60 and 0.74 but was fair for esophagogastroduodenal (kappa = 0.36). Agreement for UC extent (kappa = 0.67; 95% CI: 0.48-0.85), and CD behavior (kappa = 0.67; 95% CI: 0.49-0.83) were very good. Area under the ROC curves was greater than 0.84 for diagnosis, CD behavior, UC extent, and ileal and colonic CD location.
  
  
  CONCLUSIONS
  IBD phenotype classification using a standard protocol exhibited very good to excellent inter- and intrarater agreement and validity. This study highlights the importance of standard protocols in generating reliable and valid phenotypic assessments. The data will facilitate estimates of phenotyping misclassification rates that should be considered when making inferences from IBD genotype-phenotype studies.
authors.affiliation: Johns Hopkins University Meyerhoff Inflammatory Bowel Disease Center, Baltimore MD, USA.
authors.forename: Themistocles
authors.initials: T
authors.lastname: Dassopoulos
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Nguyen
authors.forename: Alain
authors.initials: A
authors.lastname: Bitton
authors.forename: Gillian P
authors.initials: GP
authors.lastname: Bromfield
authors.forename: L Philip
authors.initials: LP
authors.lastname: Schumm
authors.forename: Yahong
authors.initials: Y
authors.lastname: Wu
authors.forename: Abdul
authors.initials: A
authors.lastname: Elkadri
authors.forename: Miguel
authors.initials: M
authors.lastname: Regueiro
authors.forename: Benjamin
authors.initials: B
authors.lastname: Siemanowski
authors.forename: Esther A
authors.initials: EA
authors.lastname: Torres
authors.forename: Federico J
authors.initials: FJ
authors.lastname: Gregory
authors.forename: Sunanda V
authors.initials: SV
authors.lastname: Kane
authors.forename: Laura E
authors.initials: LE
authors.lastname: Harrell
authors.forename: Denis
authors.initials: D
authors.lastname: Franchimont
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Achkar
authors.forename: Anne
authors.initials: A
authors.lastname: Griffiths
authors.forename: Steven R
authors.initials: SR
authors.lastname: Brant
authors.forename: John D
authors.initials: JD
authors.lastname: Rioux
authors.forename: Kent D
authors.initials: KD
authors.lastname: Taylor
authors.forename: Richard H
authors.initials: RH
authors.lastname: Duerr
authors.forename: Mark S
authors.initials: MS
authors.lastname: Silverberg
authors.forename: Judy H
authors.initials: JH
authors.lastname: Cho
authors.forename: A Hillary
authors.initials: AH
authors.lastname: Steinhart
mesh_terms: D003093:Colitis, Ulcerative / Q000235:genetics; D003424:Crohn Disease / Q000235:genetics; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000145:classification / Q000235:genetics*; D015588:Observer Variation; D010641:Phenotype; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity