Abstract Background Perianal Crohn’s disease (pCD) is a challenging form of Crohn’s disease, which includes both fistulising and non-fistulising features, such as anorectal stricture, skin tags and erosive disease (1). Whilst non-fistulising pCD (nfpCD) can result in a significant disease burden for patients, these features are under-recognised in clinical practice, current guidelines and clinical research relating to pCD (2,3). Informed by a review of existing classification systems, this study aimed to develop a novel classification system to guide identification and management of non-fistulising pCD. Methods Following a systematic review to identify existing classification systems, a modified nominal group technique expert consensus process was used to develop a novel classification system for non-fistulising pCD. This process involved several phases including ideas generation, clarification of ideas, several rounds of voting and patient and public involvement (PPI). Results Twenty-two existing classification systems for non-fistulising pCD were identified, the majority (18/22, 88%) of which focused on categorising non-fistulising pCD. Participating panellists included multidisciplinary experts from the TOpClass consortium, with representation from 10 countries. The initial round of voting established a need for a novel classification system (n = 18 89% A+, 11% A), and passed a number of statements relating to the content of the classification. The final classification structure was passed with 100% consensus (n = 27, 93%,A+, 7% A) (Figure 1). The final statements to accompany the classification were passed with a mean 98% consensus (n = 28, 80% A+, 18% A) (Table 1). The novel structure classifies nfpCD according to the presence of stricturing disease, erosive disease and skin tags with severity ranging from minimal symptoms (Class 1) to severe symptoms requiring defunctioning ostomy (Class 2c), proctectomy (Class 3) or perineal symptoms after proctectomy (Class 4). The structure complements the existing TOpClass classification for fistulising pCD, to enable classification of patients with both fistulising and non-fistulising features of pCD. The classification system incorporates patient goals and symptom burden, and introduces a number of novel concepts, such as velocity and destruction to provide a clinically useful framework. Conclusion This expert consensus has developed a dynamic, comprehensive and patient-focused system for optimising the classification of patients with non-fistulising pCD for clinical and research use. Further validation in prospective cohorts is planned to ensure clinical applicability. References: 1. Singh B, McC Mortensen NJ, Jewell DP, George B. Perianal Crohn’s disease. British Journal of Surgery. 2004 June 17;91(7):801–14. 2. Bouguen G, Siproudhis L, Bretagne JF, Bigard MA, Peyrin-Biroulet L. Nonfistulizing perianal Crohn’s disease: Clinical features, epidemiology, and treatment. Inflamm Bowel Dis. 2010 Aug 1;16(8):1431–42. 3. Adamina M, Minozzi S, Warusavitarne J, Buskens CJ, Chaparro M, Verstockt B, et al. ECCO Guidelines on Therapeutics in Crohn’s Disease: Surgical Treatment. Journal of Crohn’s and Colitis. 2024 Oct 15;18(10):1556–82. Conflict of interest: Mr. Pelly, Theo: No Conflicts Geldof, Jeroen: Personal Fees: Jeroen Geldof has served as an advisory board member for Arena and as a speaker for Janssen and Galapagos. Anand, Easan: Nil Hanna, Luke: None Joshi, Shivani: Speaker Fees from Lilly Shakweh, Eathar: None. Panchal, Radha: None Kotze, Paulo Gustavo: Grant: Pfizer, Takeda Personal Fees: Abbvie, Johnson & Johnson, Ferring, Pfizer, Takeda, Celltrion Other: Abbvie, Janssen, Ferring, Pfizer, Takeda De Parades, Vincent: - Clinical research: Brothier, Sandoz, Takeda - Advisory boards: Abbvie - Courses, training, conferences: AAbbvie, Amgen, Biolitec, FCare Systems, Janssen, Takeda, THD lab, Tillots De Looze, Danny: No conflict of interest Powell, Nick: Grant: Takeda, BMS, Pfizer, Astra-Zeneca Personal Fees: Abbvie, Abivax, Allergan, Astra-Zeneca, Bristol-Myers Squibb, Celgene, Celltrion, Dr Falk Pharma UK Ltd, Ferring, Galapagos, GSK, Janssen, MSD, Roche, Pfizer, Sobi, Takeda, Tillotts Tozer, Philip: Personal Fees: Takeda - speakers fees, member of Inspire, and advisory boards Ferring - speakers fees Falk - speakers fees Tillott’s - speakers fees J & J - speakers fees Abbvie - speakers fees Hart, Ailsa: Grant: Takeda Personal Fees: Abbvie, Amgen, Arena, AZ, Falk, Celltrion, Eli Lilly, Ferring, Genentech/ Roche, GSK, Pfizer, Takeda, Napp, Pharmacosmos, Janssen (J & J), Bristol-Myers Squibb, Gilead, Galapagos, Alfasigma
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