Elaboration and validation of Crohn's disease anoperineal lesions consensual definitions.

Aim: To establish consensual definitions of anoperineal lesions of Crohn's (APLOC) disease and assess interobserver agreement on their diagnosis between experts.

Methods: A database of digitally recorded pictures of APLOC was examined by a coordinating group who selected two series of 20 pictures illustrating the various aspects of APLOC. A reading group comprised: eight experts from the Société Nationale Française de Colo Proctologie group of study and research in proctology and one academic dermatologist. All members of the coordinating and reading groups participated in dedicated meetings. The coordinating group initially conducted a literature review to analyse verbatim descriptions used to evaluate APLOC. The study included two phases: establishment of consensual definitions using a formal consensus method and later assessment of interobserver agreement on the diagnosis of APLOC using photos of APLOC, a standardised questionnaire and Fleiss's kappa test or descriptive statistics.

Results: Terms used in literature to evaluate visible APLOC did not include precise definitions or reference to definitions. Most of the expert reports on the first set of photos agreed with the main diagnosis but their verbatim reporting contained substantial variation. The definitions of ulceration (entity, depth, extension), anal skin tags (entity, inflammatory activity, ulcerated aspect), fistula (complexity, quality of drainage, inflammatory activity of external openings), perianal skin lesions (abscess, papules, edema, erythema) and anoperineal scars were validated. For fistulae, they decided to follow the American Gastroenterology Association's guidelines definitions. The diagnosis of ulceration (κ = 0.70), fistulae (κ = 0.75), inflammatory activity of external fistula openings (86.6% agreement), abscesses (84.6% agreement) and erythema (100% agreement) achieved a substantial degree of interobserver reproducibility.

Conclusion: This study constructed consensual definitions of APLOC and their characteristics and showed that experts have a fair level of interobserver agreement when using most of the definitions.