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Reference - VALID trial (Gut 2015 Oct;64(10):1569) (level 3 [lacking direct] evidence)
Most polyps detected in asymptomatic patients during screening colonoscopy are diminutive (≤ 5 mm) and have a very low risk of having advanced histology, yet they are routinely removed for pathology (Gastroenterology 2008 Oct;135(4):1100, Clin Gastroenterol Hepatol 2006 Mar;4(3):343, Gastroenterology 2012 Sep;143(3):844). Newer equipment and image enhancement techniques such as narrow-band imaging may increase the ability to optically diagnose diminutive polyps, but the adoption of such techniques in place of pathology has been slow (Gut 2013 Dec;62(12):1704). The European Society of Gastrointestinal Endoscopy (ESGE) has recently given a weak recommendation to the use of optical diagnosis of diminutive polyps using virtual chromoendoscopy under strictly controlled conditions with validated scales and adequate photodocumentation performed by experienced endoscopists in place of conventional histopathological testing (Endoscopy 2014 May;46(5):435). In order to not obtain a pathology evaluation, the endoscopist must have high confidence in the diagnosis. A recent randomized trial compared endoscopic confidence in optical diagnosis of diminutive polyps using near-focus view (65X) on dual-focus colonoscope vs. standard-focus view (30X) on standard colonoscope in 558 patients having routine high-definition colonoscopy. Exclusion criteria included referral for polypectomy, colitis, personal or family history of polyposis or hereditary colorectal cancer syndrome, and coagulopathy or thrombocytopenia.
All colonoscopies included an initial examination with high definition white light colonoscopy in the standard view and once polyps were detected, optical diagnosis was made using the narrow-band imaging mode. Endoscopists diagnosed each diminutive polyp as either neoplastic (tubular adenoma, villous adenoma, high-grade dysplasia, cancer) or non-neoplastic (hyperplastic, sessile serrated adenoma/polyp or inflammatory) and assigned low or high confidence levels to their diagnosis. High confidence was defined as a polyp with ≥ 1 Narrow-band Imaging International Colorectal Endoscopic (NICE) classification type 2 (neoplasia) or type 1 (non-neoplasia) feature and no features of the alternative classification type. Low confidence was assigned to polyps with features suggestive of sessile serrated adenoma/polyp and all polyps not fulfilling the high confidence criteria. All endoscopic diagnoses were compared to histopathology performed by a blinded pathologist. Overall, 975 diminutive polyps were identified in 66.1% of patients. High-confidence diagnoses were reported in 85.1% of polyps with near-focus viewing vs. 72.6% with standard-focus viewing (p < 0.0001). Compared to histopathology, high-confidence diagnoses with both near-focus and standard-focus views had high sensitivity (98.2% and 95.2%, respectively) and negative predictive values (96.4% and 92%, respectively) for the diagnosis of neoplastic diminutive polyps. Correct surveillance interval recommendations based on optical diagnoses were made in 93.5% of patients in the near-focus viewing group and 92.2% of patients with standard-focus viewing group.
The results of this trial confirm previous studies finding that narrow-banded imaging can be used to optically diagnose diminutive polyps in patients presenting for routine screening colonoscopy. Both types of viewing resulted in high-confidence diagnoses with high sensitivity and negative predictive values, indicating either protocol can help rule out neoplasia in diminutive polyps. The American Society for Gastrointestinal Endoscopy (ASGE) has proposed that diminutive polyps may be resected and discarded without histopathology if endoscopic diagnosis and histopathology are shown to have ≥ 90% agreement in surveillance interval. The ASGE has also proposed that non-neoplastic diminutive rectosigmoid polyps could be left without removal if endoscopic diagnosis had ≥ 90% negative predictive value. High-confidence diagnoses made using near-focus and standard-focus views fulfill both these criteria, although near-focus viewing was associated with a greater rate of high-confidence diagnoses than standard focus viewing. This increase in confidence translates into a greater number of polyps adequately diagnosed by endoscopists with the near-focus view compared to the standard-focus view and limits the need for pathology to low-confidence diagnoses.
Based on the results of this trial, endoscopists making high-confidence optical diagnoses can recommend surveillance intervals of 5 years for patients with neoplastic diminutive polyps and 10 years for patients with non-neoplastic polyps without confirmatory pathological testing . One caveat, however, is that if clinicians doubt the validity of this approach, they may have a tendency to recommend more frequent follow-up colonoscopies for diminutive polyps than they would for pathology-confirmed non-neoplastic polyps. If this were the case, the cost savings produced by avoiding unnecessary biopsies might be negated by an increase in colonoscopy frequency.
For more information, see the Colonoscopy topic in DynaMed and DynaMed Plus.