WASHINGTON — A withdrawal time of 6 minutes is adequate for reaching adenoma detection rates recommended by the American Society for Gastrointestinal Endoscopy, according to a large, single-institution study presented at the annual Digestive Disease Week.
The investigators performed a database analysis that confirmed previous studies that showed that a 6-minute withdrawal time during screening colonoscopy is adequate to reach detection rates of 25% in men and 15% in women over the age of 50. These rates were recommended by the U.S. Multisociety Task Force on Colorectal Cancer in 2002, and a joint task force of the American College of Gastroenterology and the American Society for Gastrointestinal Endoscopy in 2006.
The previous studies demonstrated close correlations between withdrawal time and polyp detection, said Dr. Gavin C. Harewood of Beaumont Hospital in Dublin. “The longer one takes to withdraw during colonoscopy, the higher the polyp or adenoma detection rate,” he said.
Dr. Harewood, formerly of the Mayo Clinic in Rochester, Minn., and his colleagues there reviewed the data from all outpatient colonoscopies performed at the clinic in 2003. They examined the mean withdrawal time for negative procedures and the individual polyp detection rate. Forty-three endoscopists performed 10,955 procedures, of which 9,528 were performed on patients over age 50.
The mean withdrawal time was 7 minutes for men and 6.3 minutes for women.
Polyps were detected in 4,311 patients (45.2%). The researchers analyzed the histology of a random sample of 50 polyps and found that 56% contained adenomatous tissue. By dividing the minimum recommended adenoma detection rates of 25% and 15% by 0.56, the researchers found that the minimum polyp detection rate was 45% for men and 27% for women.
The withdrawal time that corresponded to a detection rate of 45% in men was just over 6 minutes. For women, a 4.3-minute withdrawal time corresponded with the 27% detection rate.
The authors “conclude that 6 minutes is a minimum acceptable withdrawal time for colonoscopy, as it appears to correlate with the minimum recommended adenoma detection rate,” said Dr. Harewood.
Histology data were not available for all the polyps, and the study was not restricted to screening colonoscopies. In addition, the results are from a tertiary referral center, “which does limit the external validity of these findings,” he said.
Also, Dr. Harewood said, “withdrawal time [is] only part of the equation.” Some fast endoscopists may have high detection rates, while some slow practitioners might be sloppy, he said. He added, however, that the evidence is “compelling” that “withdrawal time correlates with detection.”