The review -- limited to comparing the traditional procedure to use of computer tomography as a method -- also finds that despite seeming advantage for the person being screened, there is no evidence that availability of the CT scan results in more screenings being done.
CT scanning uses computers and software to display images of the colon as if the viewer were seeing the inside of it through an endoscope, the instrument used in traditional colonoscopy. It does not require sedation, although it does require the same bowel-cleansing preparation as the older method.
The review is published by ECRI, a nonprofit health services research agency that produces systematic evidence reviews on medical devices, drugs, biotechnologies and procedures.
Because anything detected by a CT scan would necessitate a follow-up colonoscopy to confirm the finding and to remove the polyps, there is controversy over its value both to the individual and to the health care system.
Although the review included 23 studies of CT colonography, only one study, of 1,123 patients, directly compared colonoscopy and CT colonography in patients without any previous history of colorectal problems.
In that study, CT colonography detected 94 percent of polyps 10 millimeters and larger in diameter, while colonoscopy detected 88 percent of these polyps. CT colonography detected 89 percent of polyps six millimeters in diameter and larger, compared with 92 percent for colonoscopy.
"CT colonography can detect most large colorectal polyps and masses, but is less sensitive for detecting smaller polyps," the review concludes.
Other findings: