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Almost all colorectal polyps ≤5 mm are benign, yet current practice requires costly pathologic analysis. Dr Douglas Rex and colleagues from Indiana, USA developed and evaluated the validity of a simple narrow-band imaging (NBI)-based classification system for differentiating hyperplastic from adenomatous polyps. The team conducted a study in 4 phases. The first phase included the evaluation of accuracy and reliability of histologic prediction by NBI-experienced colonoscopists. The second phase involved the development of a classification based on color, vessels, and surface pattern criteria, using a modified Delphi method.  | | When all 3 criteria were used, the specificity ranged from 95% to 100% | | Gastroenteorlogy |
The third phase included validation of the component criteria by people not experienced in endoscopy or NBI analysis using 118 high-definition colorectal polyp images of known histology. Phase 4 included validation of the classification system by NBI-trained gastroenterology fellows, using still images. The researchers performed a pilot evaluation during real-time colonoscopy. The team developed a classification system for the endoscopic diagnosis of colorectal polyp histology, and established its predictive validity. When all 3 criteria were used, the specificity ranged from 95% to 100%, and the combined sensitivity ranged from 9% to 61%. The specificities of the individual criteria were lower although the sensitivities were higher. During real-time colonoscopy, endoscopists made diagnoses with high confidence for 75% of consecutive small colorectal polyps, with 89% accuracy, 98% sensitivity, and 95% negative predictive values. Dr Rex's team concluded, "We developed and established the validity of an NBI classification system that can be used to diagnose colorectal polyps." "In preliminary real-time evaluation, the system allowed endoscopic diagnoses of colorectal polyp histology."
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