Knowledge of positive cologuard test improves colonoscopy performance

Cologuard is an at-home, stool-DNA colorectal cancer screening test that has been approved by the U.S. Food and Drug Administration. This test, available by prescription only, is reimbursed by Medicare and covered by an increasing number of commercial health care plans.

Researchers from Mayo Clinic compared results of colonoscopies following a positive result from Cologuard (unblinded) with colonoscopies performed by those who were not aware of the Cologuard result (blinded). Unblinded endoscopists found polyps or hemorrhagic lesions 83 percent of the time and precancerous polyps in 70 percent of patients, compared to 68 and 53 percent of blinded endoscopists, respectively.

"Endoscopist knowledge of a positive Cologuard result appears to enhance colonoscopy quality, based on observed differences in number of detected lesions, total adenomas, detection of inconspicuous or flat lesions, and withdrawal times." says David Johnson, M.D., a gastroenterologist at Mayo Clinic's Rochester campus. "This increase in yield could translate into more true-positive and fewer false-negative results than estimated from blinded pre-approval studies." The study also showed that unblinded endoscopists spent 46 percent more time and found twice as many polyps per colonoscopy.

The blinded group included a portion of the Cologuard-positive patients who participated in the DeeP-C clinical study, which was published in the April 2014 New England Journal of Medicine. The DeeP-C study evaluated Cologuard's performance in nearly 10,000 patients. Cologuard was found to be 92 percent sensitive in detecting colorectal cancer with 87 percent specificity.

In August 2014, Mayo Clinic became the health care organization to offer Cologuard. The Cologuard technology platform was co-developed by Exact Sciences Corp. and Mayo Clinic as part of a broad, exclusive collaboration.