Outcome measurement in perianal Crohn's disease

Perianal Crohn's disease (pCD) is a distinct and debilitating phenotype of Crohn's disease and an independent predictor of long-term adverse outcomes. Traditionally, outcome measurement has focused on fistula healing to assess treatment success; however, as we recognise distinct classes of patients and shift towards shared decision making, healthcare professionals are increasingly acknowledging the importance of assessing more nuanced outcomes such as downstaging, quality of life, sex and intimacy and the impact on family, education or work. Current challenges in outcome measurement include substantial heterogeneity in definitions, measurement tools and time points used. This review will cover the current landscape, reporting on historical measurement instruments, such as the fistula drainage assessment (FDA), perianal disease activity index (PDAI) and the collective move towards patient-centred and patient-developed tools, such as the Crohn's anal fistula quality of life scale (CAF-QoL). It will also assess the value of core outcome measurement sets, which provide a uniform but flexible framework to standardise outcome reporting across studies and support comparison of interventions in clinical practice. Importantly, the incorporation of patient perspectives within their methodology ensures that their recommendations reflect outcomes that truly matter to those with pCD. The contemporary need is for novel clinical and radiological tools to monitor perianal disease activity that are predictive, preventative and provide treatment thresholds, so that patients can live well with their fistulising disease, if it cannot be eradicated. There will no doubt also be a role for digital applications and artificial intelligence in enhancing outcome measurement further for perianal Crohn's disease.