Perianal fistulising Crohn's disease (PFCD) affects up to 20% of patients with Crohn's disease (CD) and is a complex and challenging form of CD that can result in a significant illness burden 1, 2. Despite recent advances in PFCD classification systems, disease activity can be challenging to monitor on an ongoing basis when compared to luminal CD where biomarkers, imaging and colonoscopy are readily utilised in a “treat to target” approach 3. Currently, assessment of fistulas is achieved through a combination of clinical and magnetic resonance imaging (MRI) evaluations 4. However, radiological resolution generally lags months post clinical improvement and there is a lack of robust biomarkers of PFCD activity 5, 6. We read with interest the recent article by Wang et al. which presents a novel investigation into the use of fistula calprotectin as a biomarker of disease activity and treatment response in PFCD 7. In this single-centre observational study, Wang et al. demonstrate a novel use of the neutrophil cytosolic protein, calprotectin, as a biomarker of fistula activity 7. Fistula calprotectin (FiCP) concentrations obtained from scrapings of the fistula tract under local anaesthesia were correlated with histological inflammation, and clinical and radiological indices. These promising initial results highlight the potential for FiCP to be further studied as a marker of local inflammatory activity in PFCD. Furthermore, in this study, FiCP appeared to be a sensitive and specific marker of treatment response. Given the growing burden of inflammatory bowel disease worldwide, the use of cost effective and readily available biomarkers for monitoring of PFCD is an important consideration given the potential resource constraints associated with access to repeated MRI in this disease 8. The promising initial findings related to FiCP presented by Wang et al. require additional validation in multi-centre cohorts prior to any potential clinical use 7. The reproducibility of FiCP measurements, including day-to-day and inter- and intra-operator variability, and the impact of surgical management of PFCD requires assessment. Comparison of FiCP with longer term follow up and fibrosis of fistula tracts would allow for more insightful longitudinal interpretations of biomarker concentrations. Furthermore, if FiCP appears to be a reliable biomarker in additional cohorts, patient acceptability of the fistula curettage/scraping techniques used in this study to obtain samples for FiCP assessment requires consideration. In summary, tract-specific inflammation by assessment of FiCP may be a potentially useful marker for monitoring of PFCD as shown by the preliminary analyses of Wang et al. 7 However, caution should be advised before there can be any clinical application of these findings, which remains a research tool prior to the reproduction of similar results in larger, well defined validation studies. Ali Alsoudani: conceptualization, writing – original draft. Akhilesh Swaminathan: conceptualization, writing – review and editing. The authors have nothing to report. A.S. has received honoraria for educational activities from Janssen and Celltrion, and travel assistance from Dr. Falk Pharma (unrelated to this manuscript). This article is linked to Wang et al. paper. To view this article, visit https://doi.org/10.1111/apt.70600. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.
Alsoudani et al. (Mon,) studied this question.
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