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Background: Narrow-band imaging (NBI) diagnosis of colorectal lesions requires further consideration and standardized classification for attaining consensus among endoscopists.
Objective: Compare vascular findings and diagnosis of colorectal lesions using various endoscopic images to assess effectiveness of NBI with magnification.
Method: Three endoscopic factors (vascular findings; diagnosis from NBI with magnification images; and total diagnosis from all available colonoscopic images including white light endoscopy, chromoendoscopy, NBI with magnification and magnifying chromoendoscopy) for 15 colorectal lesions were evaluated by 12 expert colonoscopists (Group A), 36 endoscopists not expert in colonoscopy (Group B) and 55 individuals not medical doctors, but familiar with gastrointestinal endoscopy or other medical products (Group C). We calculated accuracy percentages for all three endoscopic factors based on responses from each group. Highest percentage for vascular finding, NBI with magnification diagnosis and total diagnosis for each lesion assumed to be opinion of each group. We compared incidence of agreement among three groups and calculated invasion depth diagnostic accuracy rate for each group.
Results: For vascular findings from NBI with magnification images, incidence of complete agreement among three groups was 46.7%, incidence of disagreement among three groups was 46.7% and incidence of complete disagreement among three groups was 6.7%. For diagnosis from NBI with magnification images and total diagnosis from all available endoscopic images, incidence of complete agreement, disagreement and complete disagreement were 40.0%, 60.0% and 0.0%, respectively, and 60.0%, 40.0% and 0.0%, respectively. Invasion depth diagnostic accuracy from NBI with magnification images and all available endoscopic images were 60.0% and 73.3%, respectively, in Group A; 46.7% and 66.7%, respectively, in Group B; and 46.6% and 60.0%, respectively, in Group C.
Conclusion: Results suggest some level of educational training is required for effective application of NBI with magnification for precise diagnosis of colorectal lesions.
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Total diagnosis in Group A had the highest diagnostic accuracy followed by total diagnosis in Group B. NBI with magnification diagnostic accuracy in Group A was lower than total diagnosis in Group B and the same as total diagnosis in Group C. NBI with magnification diagnosis in Group B and Group C produced the lowest diagnostic accuracy rates recorded in this study. These results suggest that some level of educational training is required for the effective application of NBI with magnification for precise diagnosis of colorectal lesions.
There are currently several reported classifications for NBI diagnosis of colorectal lesions1–4 so it might be some time before a consensus is reached among endoscopists on NBI with magnification diagnosis in comparison to pit pattern diagnosis and conventional endoscopic diagnosis. Throughout the floor discussion, it was evident that agreement on determining regular from irregular capillary patterns was an unresolved issue even among expert colonoscopists thereby indicating that NBI diagnosis will require further consideration and a standardized classification must be established before a consensus is possible.
Over the last 20 years, pit pattern analysis has resulted in precise endoscopic diagnosis including differential diagnosis among hyperplastic polyps, adenomas and cancers in addition to accurate depth of invasion diagnosis for early colorectal cancers.5–7 Pit pattern diagnosis is now considered more objective than conventional endoscopic diagnosis although it still remains subjective in diagnosing pit pattern irregularities.
In contrast, NBI is a recently developed method of endoscopic detection and diagnosis that has been under study for a relatively short period. NBI with magnification facilitates detailed observation of a lesion's microvascular architecture and is widely used for the endoscopic diagnosis of colorectal tumors. Although NBI with magnification has proven very useful for differential diagnosis between non-neoplastic and neoplastic lesions using capillary pattern classification,8–10 there is no consensus as yet on depth of invasion diagnosis or determining the borderline between regular and irregular networks despite some agreement on the definition of capillary irregularity.
Based on the floor discussion, we realize that our most urgent task now is to standardize a classification for diagnosis using NBI colonoscopy. A multicenter study will then be required to evaluate the diagnostic accuracy of NBI with magnification in determining invasion depth compared with the existing conventional endoscopic classification in order to build a consensus. Undoubtedly, it will be difficult to exclude interobserver variability from such an NBI classification for colorectal lesions so interpretation of NBI with magnification findings based on an objective set of standards will also be necessary. Computer-assisted analysis might be one means of reducing the subjective nature of endoscopic diagnosis. Once achieved, a highly accurate automatic identification process should substantially enhance the educational training of less-experienced endoscopists in the use of NBI with magnification for the diagnosis of colorectal lesions.