S1572 Evaluation of Rectal Swabs as a Viable Alternative to Faecal Sampling for Calprotectin Measurement in IBD Patients

Introduction: Faecal calprotectin (FC) is a validated, non-invasive biomarker widely used in the diagnosis and monitoring of inflammatory bowel disease (IBD). Faecal specimen collection, however, poses practical challenges for patients, contributing to poor return rates. This study aimed to evaluate patient perspectives on self-administered rectal swabs (RS) as an alternative to conventional faecal sampling and assess their performance in FC quantification. Methods: Adult IBD patients on biologic therapy requiring regular FC monitoring were recruited. For each participant, a conventional faecal sample produced within the preceding 24 hours, and 2 COPAN Floqswabs were collected: a faecal sample swab (FSS, swab dipped into stool) and an RS. A survey was distributed to gather views on RS usage. FC analysis was performed using a Bülhmann FCAL Turbo assay and Abbott Architect C8000 analyser, with protocol modifications for FC extraction from swabs. Statistical analyses were conducted using Graphpad Prism (ver10.3.1). Results: Twenty patients were included in the study (11 ulcerative colitis [UC], 9 Crohn’s disease [CD]; 12M, 8F). The majority (89.5%, 15/17) found RS easy to use, and 84.2% (14/17) preferred it over faecal sample collection. Responses pertaining to comfort level were equivocal, with approximately half (41.2%, 7/17) finding it comfortable. The diagnostic accuracy of RS was evaluated against matched faecal samples (gold standard). Using ≥250 μg/g as the threshold for active IBD, 20% (4/20) of patients had a positive FC test from their faecal sample. FSS showed a strong correlation with FC values from the faecal samples (r = 0.78, P < 0.0001), with a sensitivity of 75% (95% CI 30.1%-98.7%) and a specificity of 87.5% (95% CI 64%-97.8%). Even though the RS had similar sensitivity (75%, 95% CI 30.1-98.7%), it had a lower specificity of 50% (95% CI 28%-72%). Pairwise comparison revealed no significant difference in FC levels from FSS and faecal samples; FC levels yielded by RS were however significantly different from the FSS (P = 0.001) and faecal samples (P = 0.006). Conclusion: Overall, participant responses conveyed high levels of acceptability for rectal swabbing as a method of sample collection for FC testing. Whilst faecal swabs are comparable to conventional stool samples for quantification of FC levels, self-administered rectal swabs are less reliable. Their high sensitivity does however warrant further research into various collection and sample processing techniques, given strong patient preference for alternatives to traditional faecal sampling.