Background and aims: No endoscopic examination has been able to evaluate severity of ulcerative colitis (UC) by quantification. This prospective study investigated the efficacy of quantifying autofluorescence imaging (AFI) to assess the severity of UC, which captures the fluorescence emitted from intestinal tissue and then quantifies the intensity using an image-analytical software program.
Materials and methods: Eleven endoscopists separately evaluated 135 images of conventional endoscopy (CE) and AFI from a same lesion. A CE image corresponding to Mayo endoscopic subscore 0 or 1 was defined as being inactive. The fluorescence intensities of AFI were quantified using an image-analytical software program (F index; FI). Active inflammation was defined when Matts' histological grade was 2 or more. A cut-off value of the FI for active inflammation was determined using a receiver operating characteristic (ROC) analysis. The inter-observer consistency was calculated by unweighted kappa statistics.
Results: The correlation coefficient for the FI was inversely related to the histological severity (r = -0.558, p < 0.0001). The ROC analysis showed that the optimal cut-off value for the FI for active inflammation was 0.906. The average diagnostic accuracy of the FI was significantly higher than those of the CE (84.7 vs 78.5 %, p < 0.01). The kappa values for the inter-observer consistency of CE and the FI were 0.60 and 0.95 in all participants, 0.53 and 0.97 in the less-experienced endoscopists group and 0.67 and 0.93 in the expert group, respectively.
Conclusions: The quantified AFI is considered to be an accurate and objective indicator that can be used to assess the activity of ulcerative colitis, particularly for less-experienced endoscopists.
Keywords: Autofluorescence imaging; Endoscopy; Ulcerative colitis.