And the primary-care doctors had some warnings about depending upon the results from studies done at academic institutions. Dr. Lee Green, professor in the Department of Family Medicine at the University of Michigan, said the claims of 90 percent effectiveness cited in the Times story "is yet another demonstration of the difference between theory and real world practice."
"In theory, if the test were always done perfectly, it could prevent 90 percent of cancers," Green said. "The real world is a much messier place than the theories of academic sub-specialists."
Joanna Schaffhausen, a doctoral degree holder, reviews our studies day to day. She saw several problems with the study. One she mentioned was "the overall poor rate of colonoscopy screening in this study, period."
"Just 7 percent of the patients in the group that died of colon cancer were screened with colonoscopy compared to just 10 percent of those in the control group," she said. "This is an extremely low rate of screening and represents just a 3 percent difference between the study population and the control group. Because of the size of the analysis, they were still able to do their calculations, but really if you are trying to detect the effectiveness of colonoscopy you would like to see much higher screening rates."
And there were other concerns. Dr. John Petrini, president of the American Society for Gastrointestinal Endoscopy, cited several.
"The colonoscopies were performed primarily by nongastroenterologists -- family practice, surgeons and primary-care doctors -- who are not trained to the extent of gastroenterologists," he said. "Second, it is a retrospective study and may not reflect current practices, where better preparations and slower examinations techniques are being employed, as well as the increased recognition of right-sided lesions."
As for the study findings that nearly all the cancers on the right side were missed, there was a lot of comment about how these results in the right side suggest there is a problem with the study.
Dr. Douglas Rex, director of endoscopy at Indiana University Hospital in Indianapolis, who was extensively quoted in the Times story, said the study "doesn't reflect the overall literature in that there is no protection against right-sided colon cancer in this study. Other studies suggest the same trend but not a complete lack of effect in the right colon."
And colorectal surgeon Dr. Eric Kaplan of Plano, Texas, said, "I believe that some right-sided lesions may be missed, but I would be surprised at the rate being as high as quoted in the study."
Many of the gastroenterologists said you need to seek out someone who is experienced doing colonoscopy. Dr. James Church, a colorectal surgeon at the Cleveland Clinic, said people should ask their doctors about the number they have done.
"Most colonoscopists worth their salt should know their completion rate," he said. "If they don't know, move on to the next one."
How many is enough to be experienced? "I think 1,000 minimum, which is about three years' experience for a not-very-busy endoscopist," Church said.
Everybody agreed bowel preparation was critical, and Rex, who was quoted in the Times story, emphasized in the article that split preparation -- taking half of the laxative the night before the screening test and the rest in the morning -- was important.