RELIABILITY OF A CROHNS-DISEASE CLINICAL CLASSIFICATION SCHEME BASED ON DISEASE BEHAVIOR

Classification of Crohn's disease (CD) by disease behavior-either infl ammatory (INF), fibrostenotic (FS), or fistulizing/perforating (FP)-ha s been proposed as a means of assisting management decisions and predi cting outcomes for subgroup analysis in clinical trials and for making phenotype/genotype associations in molecular genetic studies. Accurat e and reproducible classification of CD patient subgroups is of paramo unt importance in such studies but to be useful, the classification sc heme must have good interrater agreement. We sought to assess the inte rrater agreement associated with the disease-behavior classification s cheme of CD. Twelve patients with CD were randomly selected from a dat abase of 964 patients with CD undergoing medical or surgical treatment or both. Clinical details of the 12 cases, along with their radiograp hs and surgical and pathological reports, were presented to a panel of 20 experts who were asked to classify each case based on the patient' s overall disease course (scenario A) and as if the patient were being entered into a clinical trial on that day (scenario B). Calculations of strength of interrater agreement were made and were expressed as th e kappa statistic (kappa), with kappa <0.2 = poor strength of agreemen t; kappa 0.21-0.4 = fair; kappa 0.41-0.6 = moderate; kappa 0.61-0.8 = good; and kappa 0.81-1.0 = very good. Five panel participants did not complete the study, and three clinical vignettes were excluded because of incomplete scoring, leaving a total of 15 panel experts assessing nine cases. Overall interrater agreement was only fair with kappa = 0. 353 for scenario A and kappa = 0.291 for scenario B. Interrater agreem ent was less when only the most straightforward case in each disease c ategory was evaluated. Classification of CD by pattern of disease beha vior yields only fair interrater agreement. This raises concerns regar ding its applicability, particularly in ongoing studies of genotype/ph enotype associations. Further refinement of disease subtypes and clear operational definitions are required.