Apparent diffusion coefficient for assessing Crohn’s disease activity: a meta-analysis

PURPOSE: To analyze relationships betweenapparent diffusion coefficient (ADC) and activity parameters of Crohn’s disease, e.g., length and wall thickness, CRP, FCP, MaRIA, CDAI, SES-CD, histologic inflammatory activity score, and the histological fibrotic score, based upon published data. MATERIALS AND METHODS: MEDLINE library, Scopus, and Embase databases were screened for association between ADC and activity parameters of Crohn’s disease in patients with Crohn’s disease up to Mai 2021. Overall, 21 studies with 1053 patients were identified. The following data were extracted from the literature: number of patients, correlation coefficients between ADC and length as well as wall thickness, CRP, FCP, MaRIA, CDAI, and SES-CD, inflammatory activity score, and fibrotic score. Associations between ADC and activity parameters were analyzed by Spearman’s correlation coefficient. The studies’ methodologic quality was evaluated by using the Quality Assessment of Diagnostic Studies (QUADAS 2) instrument, revealing a low risk of bias. RESULTS: In the overall sample, the pooled correlation coefficient between ADC and CDAI was −0.8 (95% CI = [−0.94; −0.65]), between ADC and MaRIA −0.66 (95% CI = [−0.79; −0.53]). A strong association was observed between ADC and SES-CD with a pooled correlation of −0.66 (95% CI = [−0.87; −0.46]). The pooled sensitivity to discriminate between involved and non-involved bowel segments was 0.89, with an area under the curve of 0.89 CONCLUSIONS: ADC showed strong inverse correlations with CDAI, MaRIA, and SES-CD scores. However, the role of ADC in assessing fibrotic changes in the bowel wall is limited. ADC can reflect acute inflammatory reactions but not systemic inflammation. KEY POINTS: • ADC value can reflect acute inflammatory reactions but not systemic inflammation. • ADC is inversely correlated with CDAI, MaRIA, and SES-CD. • The role of ADC in assessing fibrotic changes in the bowel wall is limited.