A blood-based prognostic biomarker in IBD

Abstract

Objective: We have previously described a prognostic transcriptional signature in CD8 T cells that separates patients with IBD into two phenotypically distinct subgroups, termed IBD1 and IBD2. Here we sought to develop a blood-based test that could identify these subgroups without cell separation, and thus be suitable for clinical use in Crohn's disease (CD) and ulcerative colitis (UC).

Design: Patients with active IBD were recruited before treatment. Transcriptomic analyses were performed on purified CD8 T cells and/or whole blood. Phenotype data were collected prospectively. IBD1/IBD2 patient subgroups were identified by consensus clustering of CD8 T cell transcriptomes. In a training cohort, machine learning was used to identify groups of genes ('classifiers') whose differential expression in whole blood recreated the IBD1/IBD2 subgroups. Genes from the best classifiers were quantitative (q)PCR optimised, and further machine learning was used to identify the optimal qPCR classifier, which was locked down for further testing. Independent validation was sought in separate cohorts of patients with CD (n=66) and UC (n=57).

Results: In both validation cohorts, a 17-gene qPCR-based classifier stratified patients into two distinct subgroups. Irrespective of the underlying diagnosis, IBDhi patients (analogous to the poor prognosis IBD1 subgroup) experienced significantly more aggressive disease than IBDlo patients (analogous to IBD2), with earlier need for treatment escalation (hazard ratio=2.65 (CD), 3.12 (UC)) and more escalations over time (for multiple escalations within 18 months: sensitivity=72.7% (CD), 100% (UC); negative predictive value=90.9% (CD), 100% (UC)).

Conclusion: This is the first validated prognostic biomarker that can predict prognosis in newly diagnosed patients with IBD and represents a step towards personalised therapy.

Keywords: Ibd basic besearch; Ibd clinical; crohn’s disease; gene expression; ulcerative colitis.

Figure 1

Development of a qPCR-based whole blood prognostic biomarker. (A) Schematic depicting the workflow for the development, optimisation and validation of the whole blood qPCR-based classifier with separate training and validation cohorts. (B) Distribution of correlation coefficients between microarray and qPCR-based measurements of gene expression for 39 genes. (C) Confidence of assignments to IBD1 and IBD2 subgroups in the training cohort using the qPCR classifier (15 informative and 2 reference genes). Colours indicate actual IBD1/IBD2 assignments based on CD8 T cell transcriptomic analysis (red=IBD1, blue=IBD2). Inset summary table depicts results using 0.5 cut-off for group assignment. CD, Crohn’s disease.

Figure 2

Validation of qPCR-based classifier in independent cohorts. (A and B) Kaplan-Meier plots of escalation-free survival for the CD validation cohort (A; n=66) and the UC validation cohort (B; n=57) as stratified by the IBDhi (IBD1 equivalent) and IBDlo (IBD2 equivalent) patient subgroups. Data are censored at 18 months. Statistical significance assessed by log-rank test. (C and D) Stacked density plots demonstrating the maximum medical therapy that was required during the first 2.5 years’ prospective follow-up of the IBDhi and IBDlo subgroups in CD (C) and UC (D). Treatments were plotted hierarchically (no treatment

Figure 3

The clinical course of Crohn’s disease (CD) is different in IBD1 and IBD2 patients. (A) Kaplan-Meier plot of escalation-free survival for CD patients in the IBD1 and IBD2 subgroups. Data are censored at 18 months. Statistical significance assessed by log-rank test. (B and C) Kaplan-Meier plots in the same format as figure part A with patients subdivided according to clinical risk (high risk=2 or more of: age <40 years at diagnosis, early need for steroids and perianal disease; B) and presence of severe features at index endoscopy (deep and extensive ulceration in at least one colonic segment or endoscopist’s global assessment; C). (D) Stacked density plots demonstrating the maximum medical therapy that was required during 5 years’ prospective follow-up in the IBD1 and IBD2 subgroups. Treatments were plotted hierarchically (no treatment

Figure 4

The clinical course of UC is different in IBD1 and IBD2 patients. (A) Kaplan-Meier plot of escalation-free survival for UC patients in the IBD1 and IBD2 subgroups. Data are censored at 18 months. Statistical significance assessed by log-rank test. (B) Kaplan-Meier plot in the same format as figure part A with patients subdivided according to endoscopic disease severity at index colonoscopy. P value calculated by comparing mild and severe cases. (C) Stacked density plots demonstrating the maximum medical therapy that was required during the first 5 years’ prospective follow-up in the IBD1 and IBD2 subgroups. Treatments were plotted hierarchically (5-ASA only