Colorectal cancer screening

In their editorial on screening for colorectal cancer, Alan Barkun and Ken Flegel exaggerated the screening rate for this disease in the United States.1 They cited a survey in which adults over 50 years of age were asked if they had ever undergone fecal occult blood testing, sigmoidoscopy or colonoscopy.2 Sixty-three percent of the respondents replied that they had; Barkun and Flegel cited this figure as evidence of greater uptake of screening in the United States. However, only 37% of the respondents in that study were defined as being “current for testing” (that is, they claimed to have undergone fecal occult blood testing in the past year, sigmoidoscopy in the past 5 years or colonoscopy in the last 10 years). This survey was subject to recall bias in 2 ways: some respondents might have wanted to show that they were aware of current screening recommendations (and thus they would have responded falsely that they had been screened) and some might have responded that they had been screened when in fact they had undergone these tests for investigation rather than screening purposes.

David Lieberman has estimated the rate of colorectal cancer screening in primary care in the United States to be between 26% and 32%.3 This rate is not much different from the rate in Canada and is not corrected to take into account patients without access to primary care.