Background and Aims Perianal fistulizing Crohn’s disease (CD-PAF) is an aggressive phenotype of Crohn’s disease (CD) defined by frequent relapses and disabling symptoms. A novel consensus classification system was recently outlined by Geldof et al. that seeks to unify disease severity with patient-centered goals but has not yet been validated. We aimed to apply this to a real-world cohort and identify factors that predict transition between classes over time.

Methods We identified all patients with CD-PAF and at least one baseline and one follow-up pelvic (pMRI). Geldof Classification, disease characteristics, and imaging indices were collected retrospectively at time periods corresponding with respective MRIs.

Results We identified 100 patients with CD-PAF of which 96 were assigned Geldof Classes 1 – 2c at baseline. Most patients (78.1%) started in Class 2b, but changes in classification were observed in 52.1% of all patients. Male sex (72.0%, 46.6%, 40.0%, p = 0.03) and prior perianal surgery (52.0% vs 44.6% vs 40.0%, p = 0.02) were more frequently observed in those with improved. Baseline pMRI indices were not associated with changes in classification, however, greater improvements in mVAI, MODIFI-CD, and PEMPAC were seen among those who improved. Linear mixed effect modeling identified only male sex (−0.31, 95% CI −0.60 to −0.02) with improvement in class.

Conclusion Geldof classification highlights the dynamic nature of CD-PAF over time, however, our ability to predict transitions between classes remains limited and requires prospective assessment. Improvement in MRI index scores over time was associated with a transition to lower Geldof classification.

Matthew Schroeder: No relevant conflicts of interest exist Suha Abushamma: No relevant conflicts of interest exist Alvin T. George: No relevant conflicts of interest exist Ravella Balakrishna: No relevant conflicts of interest exist John Hickman: No relevant conflicts of interest exist Anusha Elumalai: No relevant conflicts of interest exist. Paul Wise: No relevant conflicts of interest exist Maria Zulfiqar: No relevant conflicts of interest exist Daniel R Ludwig: No relevant conflicts of interest exist Anup Shetty: No relevant conflicts of interest exist Satish E. Viswanath: Research support from an Investigator-Initiated Study from Takeda Pharmaceutical Chongliang Luo: No relevant conflicts of interest exist Shaji Sebastian: Received consulting fees and advisory board fees from Eli Lilly, BMS, Takeda, AbbVie, Merck, Ferring, Pharmacocosmos, Warner Chilcott, Janssen, Falk Pharma, Biohit, TriGenix, Celgene, and Tillots Pharma; speaker honoraria from AbbVie, Takeda, Celltrion, Pfizer, Biogen, AbbVie, Janssen, Merck, Warner Chilcott, and Falk, Research grants from Abbvie, Takeda, Pfizer, Tillots Pharma, Amgen, Janssen David H. Ballard: Research support from an Investigator-Initiated Study from Takeda Pharmaceuticals Parakkal Deepak: Consultant or on an advisory board for Janssen, Pfizer, Prometheus Biosciences, Boehringer Ingelheim, AbbVie, Arena Pharmaceuticals, Boehringer Ingelheim, CorEvitas LLC and Scipher Medicine Corporation. He has also received funding under a sponsored research agreement unrelated to the data in the paper from Takeda Pharmaceutical, Arena Pharmaceuticals, Bristol Myers Squibb-Celgene, and Boehringer Ingelheim.

Dr. Deepak is supported by a Junior Faculty Development Award from the American College of Gastroenterology and IBD Plexus of the Crohn's & Colitis Foundation. This project was supported by the NIH/National Center for Advancing Translational Sciences (NCATS), CTSA grant #UL1 TR002345 and Washington University DDRCC (NIDDK P30 DK052574).

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