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* = Presenting author

P262 Protein biomarker measurement in non-invasively collected colonic mucus samples as a new approach to inflammatory bowel disease (IBD) detection.

A. Loktionov*1, V. Chhaya2, T. Bandaletova1, A. Poullis2

1DiagNodus Ltd, N/A, Cambridge, United Kingdom, 2St George's NHS Trust, Gastroenterology, London, United Kingdom

Background

The detection of biomarkers in non-invasively collected samples is an attractive approach to IBD diagnosis and monitoring. The only clinically accepted method of this type is calprotectin determination in stool, which requires inconvenient stool sample preparation. We have developed a new technique of non-invasive collection of material rich in colonic mucus from the surface of the anal area immediately following defaecation. Quantitative testing of a group of IBD-related protein biomarkers comprising Eosinophil-derived Neurotoxin (EDN), Calprotectin, Protein S100A12 (markers of inflammation) and Soluble Cytokeratin 18 (CK18, epithelial cell death marker) was undertaken in a pilot study addressing IBD detection and differentiation from irritable bowel syndrome (IBS). Preliminary Results of the study are presented.

Methods

Excreted colorectal mucocellular layer samples were obtained by the new technique from 58 patients with active IBD (27 CD cases and 31 UC cases), 49 patients with IBS and 33 healthy volunteers. Protein biomarkers were quantitatively analysed in the samples using ELISA assays for EDN, Calprotectin, Protein S100A12 and CK18. The Results were expressed as biomarker amount per ml of sample lysate. Result distributions and statistics by group as well as values of test sensitivity and specificity were determined for each biomarker.

Results

Patients with IBD had significantly higher mean values for all biomarkers analysed compared to both IBS and control groups. EDN appeared to be the best biomarker for IBD detection. Its average (M±SE) levels were 181.97 ± 19.18ng/ml, 15.92 ± 5.44ng/ml and 6.26 ± 2.15ng/ml for IBD, IBS and control groups respectively. For the same groups average Calprotectin levels were 14.10 ± 1.44µg/ml, 2.18 ± 0.33µg/ml and 2.15 ± 0.82µg/ml respectively. Intergroup differences detected for S100A12 and CK18 were less pronounced. ROC curve analysis for discriminating between IBD and IBS by EDN quantification produced sensitivity and specificity values of 82.8% and 91.8% respectively (AUC=0.896). Sensitivity and specificity values for Calprotectin were 75.9% and 91.8% respectively (AUC=0.893). When the Results of the EDN and Calprotectin tests were combined using a simple algorithm, the sensitivity and specificity levels for the combined test were 91.4% and 87.8% respectively (AUC=0.931).

Conclusion

The Results show that our new method of non-invasive collection of colonic mucocellular layer samples provides material suitable for quantitative analysis of biomarkers and allows efficient IBD detection and also discrimination between IBD and IBS. The best diagnostic Results were achieved by using a combined test based upon simultaneous measurement of EDN and Calprotectin.