Validation of Red Dichromatic Imaging Score (RDI Score) to Evaluate the Severity of Ulcerative Colitis

Red dichromatic imaging (RDI) is a new imaging technology that has been closely correlated with the activity index of ulcerative colitis (UC). Although the RDI score has been developed no study has validated a correlation between the RDI score and the activity index of UC. Therefore, this study aims to validate the RDI score prospectively. A total of 34 patients with UC in whom colonoscopy was scheduled between May 2019 and October 2021 at our hospital were enrolled prospectively. MES, UCEIS, RDI scores, and Nancy index were evaluated in a blinded fashion. We evaluated the correlation between RDI and WLI scores using still images with histology. We analyzed 191 sites of colorectum. RDI score showed the positive correlation with UCEIS (r = 0.74 P < 0.0001) and MES (r = 0.78 P < 0.0001). RDI score also showed the positive correlation with Nancy index (r = 0.63 P < 0.0001). RDI score was more strongly correlated with Nancy index than UCEIS (r = 0.51) and MES (r = 0.48). When comparing still images of RDI and WLI scores, we showed RDI had a higher correlation to histology than WLI. The University Hospital Medical Information Network (UMIN000041750)