Development and Investigation of a Non-invasive Disease Severity Index for Inflammatory Bowel Disease

Abstract

Introduction: The disease severity index [DSI] encapsulates the inflammatory bowel disease [IBD] burden but requires endoscopic investigations.This study developed a non-invasive DSI using faecal calprotectin [DSI-fCal] and faecal myeloperoxidase [DSI-fMPO] instead of colonoscopy. Methods: Adults with IBD were recruited prospectively. Baseline biomarker concentrations were used to develop DSI-fCal and DSI-fMPO, and these were correlated with the original DSI, IBD symptoms, endoscopic activity, and quality of life [QoL]. Areas under the receiver operating characteristic curves [AUROC] assessed DSI-fCal and DSI-fMPO as predictors of clinical and biochemical remission at 6 months [symptom remission and fCal < 150 μg/g, respectively], and a complicated IBD-course at 24 months [disease relapse needing escalation of biologics or immunomodulators, recurrent corticosteroids, IBD hospitalisations, and/or surgeries]. Multivariable logistic regression assessed the utility of DSI-fCal and DSI-fMPO in predicting a complicated IBD course at 24 months. Results: In total, 171 patients were included (Crohn’s disease = 99, female = 90, median age = 46 years, interquartile range [IQR] 36–59]). DSI-fCal and DSI-fMPO correlated with the original DSI [r > 0.9, p < 0.001], endoscopic indices [r = 0.45–0.49, p < 0.001], IBD symptoms [r = 0.53–0.58, p < 0.001] and QoL [r = -0.57–0.58, p < 0.001]. Baseline DSI-fCal [AUROC = 0.79, 95% CI 0.65–0.92] and DSI-fMPO [AUROC = 0.80, 95% CI 0.67–0.93] were associated with 6-month clinical and biochemical remission. DSI-fCal [AUROC = 0.83, 95% CI 0.77–0.89] and DSI-fMPO [AUROC = 0.80, 95% CI 0.73–0.87] performed similarly in predicting a complicated IBD course to the original DSI [pdifference > 0.05]. The non-invasive DSI was independently associated with a complicated IBD course on multivariable analyses [DSI-fCal28, aOR = 6.04, 95% CI 2.42–15.08; DSI-fMPO25, aOR = 7.84, 95% CI 2.96–20.73]. Conclusions: The DSI-fCal and DSI-fMPO perform similarly in prognosticating the longitudinal disease course as the original DSI, whilst avoiding a need for an endoscopic assessment.