Serum proteomic profiling at diagnosis predicts clinical course, and need for intensification of treatment in inflammatory bowel disease.

Background Success in personalised medicine in complex disease is critically dependent on biomarker discovery. We profiled serum proteins using a novel proximity extension assay (PEA) to identify diagnostic and prognostic biomarkers in inflammatory bowel disease (IBD). Methods We conducted a prospective case-control study in an inception cohort of 552 patients (328 IBD, 224 non-IBD), profiling proteins recruited across 6 centres. Treatment escalation was characterised by the need for biological agents or surgery after initial disease remission. Nested leave-one-out cross validation was used to examine the performance of diagnostic and prognostic proteins. Results A total of 66 serum proteins differentiated IBD from symptomatic non-IBD controls including MMP-12 (Holm adjusted p=4.1×10 -23 ) and OSM (p=3.7×10 -16). Nine of these proteins associate with cis- germline variation (59 independent SNPs). Fifteen proteins, all members of TNF independent pathways including IL-1 and OSM predicted escalation, over a median follow-up of 518 (IQR 224-756) days. Nested cross-validation of the entire data set allows characterisation of 5-protein-models (96% comprising five core proteins ITGAV, EpCAM, IL18, SLAMF7, and IL8) which define a high-risk subgroup in IBD (HR 3.90, CI: 2.43-6.26), or allows distinct 2, and 3 protein models for UC and CD respectively. Conclusion We have characterised a simple oligo-protein panel that has the potential to identify IBD from symptomatic controls and to predict future disease course. Further prospective work is required to validate our findings.