Background and study aims: In vivo optical diagnosis of small colorectal polyps has potential clinical and cost
advantages, but requires accuracy and high interobserver agreement for clinically
acceptability. We aimed to assess interobserver variability and diagnostic performance
of endoscopic imaging modalities in characterizing small colonic polyps.
Methods: High quality still images of 80 polyps < 1 cm were recorded using white-light endoscopy
(WLE), autofluorescence imaging (AFI) and narrow-band imaging with and without magnification
(NBI and NBImag). All images were assessed for quality, prediction of polyp histology,
and vascular pattern intensity (with NBI) by nine experienced colonoscopists (four
experts in advanced imaging) from five UK centers. Interobserver agreement (kappa
statistic), sensitivity, specificity, and accuracy were calculated compared with histopathological
findings.
Results: Interobserver agreement for predicting polyp histology using NBImag was significantly
better for experts (κ = 0.63, substantial) compared with nonexperts (κ = 0.30, fair;
P < 0.001), and was moderate for all colonoscopists with WLE, AFI and NBI. Interobserver
agreement for vascular pattern intensity using NBI was 0.69 (substantial) for experts
and 0.57 (good) for nonexperts. NBImag had higher sensitivity than WLE (experts, 0.93
vs. 0.68, P < 0.001; nonexperts, 0.90 vs. 0.52, P < 0.001) and higher overall accuracy (experts, 0.76 vs. 0.64, P = 0.003; nonexperts 0.61 vs. 0.40, P < 0.001). AFI had worse accuracy than WLE for both expert colonoscopists (0.53 vs.
0.64, P = 0.02) and nonexperts (0.32 vs. 0.40, P = 0.04).
Conclusions: Of the imaging modalities tested, NBImag appeared to have the best overall accuracy
and interobserver agreement, although not adequate for in vivo diagnosis. NBI and
AFI did not have better sensitivity, specificity, or accuracy compared with WLE.
References
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