A teaching video entitled “Optical Diagnosis of Colorectal Polyps” is available through the American Society for Gastrointestinal Endoscopy On-line Learning Center. The program outlines the steps necessary to practice the technique. It provides a review of the concepts of optical diagnosis and numerous illustrative case examples.
Documentation of competence
The documentation of successful completion of training is important. The formal training should be based on a validated tool, should be periodic, and should include an in vivo component. Ex vivo competency should be assessed before evaluation of clinical performance. After achievement of ex vivo performance thresholds, study participants should then be evaluated in real time to ensure sustained performance before study initiation. Finally, and consistent with the Plan-Do-Study-Act quality improvement model, participants should undergo additional ex vivo testing periodically throughout the study to ensure sustained performance and evaluate the need for further training. By using this approach of regular self-training and a robust teaching tool, we observed no significant difference in a group of experienced endoscopists between performance in the first and second halves of the study. Agreement in surveillance interval recommendations between optical-based and pathology-based strategies exceeded 95% in both halves of the study.7,8
Standardized optical diagnostic criteria
When feasible, investigators should use validated criteria for the endoscopic diagnosis of colorectal polyps. An example is the Narrow Band Imaging International Colorectal Endoscopic (NICE) classification by using NBI, which describes real-time differentiation of non-neoplastic (type 1) and neoplastic (type 2) colorectal polyps,9 as well as for lesions with deep submucosal invasion (type 3). Other endoscopic classifications of colorectal polyps by using NBI, i-Scan, or chromoendoscopy have been described with and without optical magnification but have not yet been validated.
Although sessile serrated adenoma/polyps exhibit features of non-neoplastic lesions, their distinction from hyperplastic polyps is challenging because of the variations in pathologic diagnoses. Until such endoscopic and pathologic distinctions are further described, investigated, and reproducible, it may be necessary to remove and submit to pathology all proximal and/or large NICE type 1 polyps.
Training should include a working definition of the application of confidence levels. The principle of confidence levels (high vs. low) is easily understood but lacks a formal operational definition. A recent study suggested that the speed of the diagnostic determination correlated with confidence, with a cutoff of 5 seconds predicting high confidence. Five expert endoscopists performed optical diagnosis of 1309 polyps in 558 patients. The average time to diagnosis was 20 seconds, and this was an independent predictor of accuracy. An optical diagnosis made in 5 seconds or less had an accuracy greater than 90%, with 90% high-confidence determinations; those made in 6–60 seconds had an accuracy of 85%, with 77% high confidence, and diagnoses that took more than 60 seconds had an accuracy of 68%, with only 64% high confidence.
Standardized pathologic diagnostic criteria
It is critically important to use a diagnostic standard for the colorectal polyp histopathology. The World Health Organization criteria have been the most used. It is key to recognize that even standardized pathology is not a gold standard but rather a reference standard, which is often less than 100% accurate. In clinical practice, many diminutive polyps are not retrieved after polypectomy (6%–13%), are unsuitable for analysis because of diathermy artifacts (7%–19%), or may be misclassified because of incorrect orientation or limited sectioning. Furthermore, errors in differentiating conventional adenomas from hyperplastic/serrated lesions by pathologists can be as high as 10%. This may be because the normal surrounding tissue in a polypectomy specimen of a diminutive lesion has been sectioned and interpreted. Efforts to strengthen pathology as a reference standard in clinical trials must be taken, including the need to have centralized blinded pathology reading and the need to perform re-cuts of the individual polyp specimens, especially those that are interpreted by pathologists as normal tissue.
Standardized outcomes
The ASGE Preservation and Incorporation of Valuable Endoscopic Innovations working group has established a priori diagnostic thresholds for real-time endoscopic assessment of the histology of diminutive colorectal polyps.10 These thresholds are meant to define clinically important roles for imaging technology and acceptable thresholds of performance for which ASGE could support their use as an alternative paradigm for management of diminutive polyps in clinical practice. These are the two proposed thresholds for optical diagnosis. (1) For colorectal polyps ≤5 mm in size to be resected and discarded without pathologic assessment, endoscopic technology (when used with high confidence) and histopathologic assessment of polyps ≤5 mm in size should provide ≥90% agreement in assignment of post-polypectomy surveillance intervals when compared with decisions that are based on pathology assessment of all identified polyps. (2) For a technology to be used to guide the decision to leave suspected rectosigmoid hyperplastic polyps ≤5 mm in size in place (without resection), the technology should provide ≥90% negative predictive value (when used with high confidence) for adenomatous histology.
