Preclinical protein signatures in blood predict Crohn's disease and Ulcerative colitis several years before the diagnosis

Background: We aimed to identify protein signatures predictive of a future diagnosis of inflammatory bowel disease (IBD). Methods: We conducted a case-control study, nested within large population-based cohorts with biorepositories. Samples were obtained from individuals who later in life were diagnosed with IBD (preclinical cases) and compared with age and sex-matched individuals who remained free from IBD during follow-up (controls). Using proximity extension assays (Olink, Uppsala), we measured 176 proteins. We applied regularized logistic regression to identify protein signatures of preclinical disease in serum from the discovery cohort (n=312). Their performance was validated in an external preclinical cohort (n=222). The biological relevance of identified proteins was further assessed in an inception cohort (n=144). Finally, we used an IBD twin cohort (n=327) to examine the impact of genetic and shared environmental factors on identified proteins. Results: We identified 34 proteins associated with preclinical Crohn’s disease (CD) in the discovery cohort (Pfalse discovery rate <0.10), with 9 confirmed in the validation cohort (Pfalse discovery rate <0.05). For preclinical ulcerative colitis (UC), 45 proteins were identified and 12 validated (Fig. 1A-B). In the discovery cohort, a signature of 29 proteins differentiated preclinical CD cases from controls with an AUC of 0.85 (Fig. 1G). Its performance was confirmed when applied to the preclinical validation cohort (AUC=0.84, Fig. 1H). Moreover, the signature had excellent capacity to differentiate newly diagnosed CD from healthy controls in the inception cohort (AUC = 0.99, Fig. 1I). The preclinical UC signature had a significant, but albeit lower, predictive capacity in the discovery (AUC=0.77), validation (AUC=0.67) and inception cohort (AUC=0.90, Fig. 1G-I).15 of 17 proteins associated with preclinical IBD demonstrated significantly higher intra-pair correlation coefficients in healthy monozygotic- compa