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Adenoma Detection Rates Vary Substantially

A key predictor is withdrawal time during colonoscopy.

The U.S. Multi-Society Task Force and a joint task force of the American College of Gastroenterology and the American Society for Gastrointestinal Endoscopy both confirm that in patients (age, 50) who undergo first-time colonoscopy, one or more adenomas will be present in at least 25% of men and 15% of women. To fully detect prevalent adenomas, colonoscopy withdrawal times should average at least 6 minutes, exclusive of time for biopsy or polypectomy. Evidence supporting these recommendations continues to emerge (Journal Watch Gastroenterology Dec 15 2006), with the latest information coming from a private practice in Rockford, Illinois.

During a 13-month period, 12 gastroenterologists (who had each performed at least 3000 prior colonoscopies) conducted 2053 screening examinations in older patients who had not undergone previous colonoscopy. Overall mean withdrawal time during colonoscopies that did not include polypectomy was 6.3±3.9 minutes (range, 3.1–16.8 min). The overall mean rate of adenoma detection was 0.47 per colonoscopy (range, 0.10–1.05), and the rate of advanced adenoma detection was 0.06 (range, 0.01–0.10). Longer withdrawal times were strongly correlated with higher adenoma detection rates.

In a stratified analysis, physicians were grouped by their mean withdrawal times (6 min vs. >6 min) for exams that did not include polypectomy. Those with longer average withdrawal times had higher proportions of patients with any adenomas (28.3% vs. 11.8%; P<0.001), higher proportions of patients with advanced adenomas (6.4% vs. 2.6%; P=0.005), and greater numbers of adenomas detected per screened subject (0.61 vs. 0.17; P=0.006).

Comment: These results strongly support the concept that spending more time during colonoscopy results in better adenoma detection. For now, an average withdrawal time of at least 6 minutes appears to be appropriate, but the primary endpoint for quality of mucosal inspection is still the prevalence of adenomas detected in older people. This is a landmark study because it presents several features of mucosal inspection that vary greatly and that have not been reported previously. First is the dramatic range of detection for adenomas. No prior study has documented a 10-fold variation across experienced endoscopists, and the clinicians in this group clearly were not clustered at one end of this range but were spread along it in a manner that correlated with their average withdrawal times for normal colonoscopies. Second, this study demonstrates the variability in detecting not only small adenomas but also large ones. Although some might disagree about the importance of detecting small adenomas, almost no one would argue that variable detection of large adenomas is not important. Finally, this study demonstrates a correlation between detection of small adenomas and large adenomas, which validates the concept that detection of any adenoma (or number of adenomas per colonoscopy performed) is a good surrogate marker for detection of clinically relevant endpoints (such as large adenomas) that are considerably more difficult and time-consuming to measure.

— Douglas K. Rex, MD

Published in Journal Watch Gastroenterology January 12, 2007

Citation(s):

Barclay RL et al. Colonoscopic withdrawal times and adenoma detection during screening colonoscopy. N Engl J Med 2006 Dec 14; 355:2533-41.

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