Abstract
Background and study aim Advanced endoscopic imaging has revolutionized the characterization of lesions during
colonoscopy. The aim of this study was to create a new classification for differentiating
subcentimetric hyperplastic and adenomatous polyps, and deeply invasive malignant
lesions using blue-light imaging (BLI) with high definition, with and without optical
magnification, as well as to assess its interobserver concordance.
Methods A video library consisting of 48 videos/still images (with/without optical magnification)
from 24 histologically verified polyps/cancer with BLI was prospectively created.
In the first step, seven endoscopists with experience in electronic chromoendoscopy
reviewed 12 BLI videos/still images with/without magnification representative of the
different histotypes, and individually identified possible descriptors. In the second
step, these descriptors were categorized and summarized with a modified Delphi methodology.
In the third step, the seven endoscopists independently reviewed the remaining 36
videos/still images with/without optical magnification, and the interobserver agreement
for the new descriptors was assessed. The interobserver agreement between endoscopists
was assessed using Gwet’s AC1.
Results By reviewing the initial 12 videos/still images, 43 descriptors were proposed. By
a modified Delphi process, the endoscopists eventually agreed on summarizing 12 descriptors
into three main domains. The main domains identified were: polyp surface (mucus, yes/no;
regular/irregular; [pseudo]depressed, yes/no), pit appearance (featureless, yes/no;
round/nonround with/without dark spots; homogeneous/heterogeneous distribution with/without
focal loss), and vessels (present/absent, lacy, pericryptal, irregular). Interobserver
agreement for the polyp surface domain appeared to be almost perfect for mucus (AC1
0.92 with and 0.88 without optical magnification), substantial for the regular/irregular
surface (AC1 0.67 with and 0.66 without optical magnification). For the pit appearance
domain, interobserver agreement was good for featureless (AC1 0.9 with and 0.8 without
optical magnification), and round/nonround (AC1 0.77 with and 0.69 without optical
magnification) descriptors, but less consistent for the homogeneity of distribution
(AC1 with/without optical magnification 0.58). Agreement was almost perfect for the
vessel domain (AC1 0.81 – 0.85).
Conclusions The new BASIC classification takes into account both morphological features of the
polyp, as well as crypt and vessel characteristics. A high concordance among the observers
was shown for most of the summarized descriptors. Optical magnification had a beneficial
effect in terms of interobserver agreement for most of the descriptors.
