P0449 qFIT as a predictor of relapse in quiescent Crohn’s disease – initial results from the Stratifying Crohn’s Using Biomarker Assessment (SCUBA) study
Authors: Palmer J , Catchpole A , Talwar D , Veryan J , Colbert R , Seenan J P , Macdonald J , Gerasimidis K , Gaya D R 
Published: January 2025

Abstract

Background
The Stratifying Crohn’s Using Biomarker Assessment (SCUBA) study assessed a number of biomarkers (Faecal Calprotectin (FCP), quantitative faecal immunochemical testing (qFIT), C reactive protein (CRP), plasma and faecal zinc) in their ability to predict relapse in quiescent Crohn’s disease (CD). FCP is widely utilised as a surrogate marker in the monitoring of CD but is labour intensive and expensive. Population qFIT testing is established in colorectal cancer screening and is relatively cheap and simple to analyse. qFIT has been shown to predict relapse in ulcerative colitis1. Here we present a comparison of qFIT and FCP at predicting relapse in quiescent luminal CD.

Methods
A single centre prospective cohort study was performed. Patients with clinically quiescent CD (Harvey Bradshaw Index ≤3) were identified and provided paired, baseline FCP, qFIT and routine biochemical workup. Patients over 50 years were excluded due to overlay with bowel cancer screening programmes as were those with isolated upper GI or perianal disease. Patients were followed up over 1 year or until relapse defined by need for escalation of CD related treatment, steroids, surgery or hospitalisation for CD.

Results
274 patients were recruited with 211 returning paired baseline faecal samples. Median age was 34 years (range 18-49) and 108/211 (51.1%) were female. Median HBI at submission was 1 and median FCP, qFIT and CRP was 61µg/g stool, 9 µg Hb/g and 2 mg/l respectively. 42/211 (19.9%) experienced a relapse during follow up. Both FCP and qFIT showed good ability to predict relapse at 1 year, performing comparably, with the area under the receiver operating characteristic curves (AUROC) 0.80 (95% CI 0.74- 0.85) vs 0.75 (95% CI 0.68-0.80)(p=0.28). Combination biomarker use did not significantly improve performance, AUROC 0.82 (95%CI 0.76- 0.87) p=0.34 and p=0.07 respectively. Optimal threshold for prediction of relapse was &gt;180 µg/g stool for FCP (sensitivity 0.69 and specificity 0.85) and &gt;9 µg Hb/g for qFIT (sensitivity 0.65 and specificity 0.82). Utilising these thresholds (figure 1) patients with both FCP and qFIT above threshold had a probability of relapse free survival of 16.7% (95% CI 0.20%-31.6%) at 1 year vs 95.4% (95% CI 91.7%-99.0%, p&lt;.0001) in patients under threshold. In combination, FCP and qFIT had a positive predictive value of 50.1% and negative predictive value (NPV) of 97.6%.

Conclusion
qFIT performs well and comparably to FCP in predicting relapse in clinically quiescent luminal CD and may be used in preference to FCP being an easier and cheaper test to undertake. When combined at optimal thresholds, qFIT & FCP show significant discriminatory ability in prediction of CD relapse-free survival with an excellent NPV.

References
1.S H, J K, A N, et al. Consecutive Measurements by Faecal Immunochemical Test in Quiescent Ulcerative Colitis Patients Can Detect Clinical Relapse - PubMed. Journal of Crohn’s & colitis. 2016 Jun;10(6)doi:10.1093/ecco-jcc/jjw025