Validation of the Simplified Magnetic Resonance Index of Activity [sMARIA] Without Gadolinium-enhanced Sequences for Crohn's Disease

Background: Gadolinium-enhanced sequences are not included in the simplified Magnetic Resonance Index of Activity [sMARIA], but in the derivation of this index readers had access to these sequences. The current study aimed to validate the sMARIA without gadolinium-enhanced sequences for assessing disease activity, severity, and response to treatment in patients with Crohn's disease. Methods: We prospectively included patients with active Crohn's disease and at least one segment with severe inflammation [ulcers] at ileocolonoscopy, who required treatment with biologic drugs. Patients were evaluated by both magnetic resonance enterography [MRE] and ileocolonoscopy at baseline and 46 weeks after initiation of medical treatment. We compared the quantification of disease activity and response to treatment with sMARIA versus with ileocolonoscopy Crohn's Disease Index of Severity [CDEIS], considered the gold standard. Results: Data from both MRE and ileocolonoscopy 46 weeks after treatment initiation were available for 39 of the 50 patients. As in the derivation study, the optimal cutoffs were sMARIA >= 1 for predicting active disease (area under the curve [AUC] 0.92) and sMARIA >= 2 for predicting the presence of ulcers at ileocolonoscopy [AUC 0.93]. In evaluating the response to treatment, the sMARIA detected endoscopic ulcer healing at the segment level [sMARIA < 2] with 89.5% sensitivity and 87.5% specificity. The sMARIA decreased significantly [p < 0.001] in segments achieving endoscopic ulcer healing, but did not change [p = 0.222] in segments with persistent ulceration. Conclusions: The sMARIA is accurate and reliable in quantifying disease activity and response to treatment in luminal Crohn's disease, without the need for gadolinium-enhanced sequences.