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Abstract
In 2002, the U.S. Preventive Services Task Force (USPSTF) recommended colorectal cancer
screening for adults 50 years of age or older but concluded that evidence was insufficient
to prioritize among screening tests or evaluate newer tests, such as computed tomographic
(CT) colonography.
To review evidence related to knowledge gaps identified by the 2002 recommendation
and to consider community performance of screening endoscopy, including harms.
MEDLINE, Cochrane Library, expert suggestions, and bibliographic reviews.
Eligible studies reported performance of colorectal cancer screening tests or health
outcomes in average-risk populations and were at least of fair quality according to
design-specific USPSTF criteria, as determined by 2 reviewers.
Two reviewers verified extracted data.
Four fecal immunochemical tests have superior sensitivity (range, 61% to 91%), and
some have similar specificity (97% to 98%), to the Hemoccult II fecal occult blood
test (Beckman Coulter, Fullerton, California). Tradeoffs between superior sensitivity
and reduced specificity occur with high-sensitivity guaiac tests and fecal DNA, with
other important uncertainties for fecal DNA. In settings with sufficient quality control,
CT colonography is as sensitive as colonoscopy for large adenomas and colorectal cancer.
Uncertainties remain for smaller polyps and frequency of colonoscopy referral. We
did not find good estimates of community endoscopy accuracy; serious harms occur in
2.8 per 1000 screening colonoscopies and are 10-fold less common with flexible sigmoidoscopy.
The accuracy and harms of screening tests were reviewed after only a single application.
Fecal tests with better sensitivity and similar specificity are reasonable substitutes
for traditional fecal occult blood testing, although modeling may be needed to determine
all tradeoffs. Computed tomographic colonography seems as likely as colonoscopy to
detect lesions 10 mm or greater but may be less sensitive for smaller adenomas. Potential
radiation-related harms, the effect of extracolonic findings, and the accuracy of
test performance of CT colonography in community settings remain uncertain. Emphasis
on quality standards is important for implementing any operator-dependent colorectal
cancer screening test.