OP17 Defining radiological healing in perianal fistulising Crohn’s Disease: a global modified Delphi consensus
Authors: Anand Mr E , Devi J , Joshi S , Antoniou A , Ballard D H , Deepak P , Stoker J , Lung P , Hart A , Tozer P ,   TOpCLASS consortium
Published: January 2025

Abstract

Background
Perianal fistulizing Crohn’s disease (pfCD) poses a significant challenge, requiring precise endpoints in clinical trials to evaluate the effectiveness of therapies. While Magnetic Resonance Imaging (MRI) is the gold standard for assessing fistula healing, variability in radiological definitions complicates clinical trial design and real-world treatment evaluations. This study aimed to achieve international consensus on the definition of radiological healing in pfCD.

Methods
This two-phase study was conducted by the Treatment Optimisation and CLASSification of perianal Crohn’s Disease (TOpCLASS) consortium.
Phase 1 involved a systematic review to identify MRI-based variables and indices used to define radiological healing in pfCD, with the protocol registered on PROSPERO (CRD42024504334). The methodological quality of these indices was assessed using the COnsensus-based standards for the selection of Measurement INstruments (COSMIN) framework. A comprehensive list of variables was generated for the subsequent questionnaire.
In Phase 2, an online modified Delphi consensus process was used, involving international pfCD experts. Two rounds of surveys were conducted, followed by a final stakeholder meeting to achieve consensus. An agreement threshold of &gt;80% was set for consensus items, with results reported according to Accurate Consensus Reporting Document (ACCORD) guidelines.

Results
Eighty-four experts from 16 countries participated in the Delphi process. A strong consensus (&gt;95%) was reached on defining a radiologically healed fistula as the absence of T2-weighted hyperintensity, a completely fibrotic fistula tract and, when contrast is used, the absence of contrast enhancement on post-contrast T1-weighted images (Table 1).
Radiological improvement was defined (80% consensus) as an unequivocal reduction in one or more of the following: T2-weighted hyperintensity, fistula diameter, length, abscess size, or a predominantly fibrous fistula tract. A reduction in hyperintensity on contrast-enhanced T1-weighted images also indicated improvement (Table 1).
Other findings on MRI timing, surgical interventions, advanced therapies, MRI sequences, and central reading recommendations are shown in Figure 2.

Conclusion
This international consensus represents a major step toward standardizing radiological endpoints in pfCD. Adoption of this definition will improve the consistency and reliability of pfCD assessments in clinical care and research. Future studies are underway to validate the definition and examine how changes in MRI variables predict long-term outcomes and quality of life improvements.

References
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