This Article  • Full text  • PDF  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Contact me when this article is cited  Related Content  • Related letters  • Similar articles in JAMA  Topic Collections  • Gastrointestinal Diseases  • Statistics and Research Methods  • Surgical Interventions  • Colorectal Surgery  • Oncology  • Colon Cancer  • Alert me on articles by topic

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

To the Editor: Dr Singh and colleagues¹ report that a negative colonoscopy is associated with a standardized incidence ratio (SIR) of 0.55 to 0.69 for subsequent colon cancer relative to the general population. However, in reaching conclusions about the predictive value of a negative colonoscopy, there are 2 other factors that must be considered.

First, by design the authors have created a low-risk cohort by excluding individuals at highest risk for CRC (eg, those with a history of inflammatory bowel disease, prior CRC, or colonoscopy within the past 5 years). Thus, the SIR would already be expected to be below 1 (ie, below average).

Second, studying persons who have all had colonoscopy may also introduce a bias, although the direction would be unclear. It could result in a high-risk group because many may have been symptomatic or had a family history of colon cancer. Conversely, colonoscopy may be a marker . . . [Full Text of this Article]

Douglas J. Robertson, MD, MPH
douglas.robertson@med.va.gov

Brenda E. Sirovich, MD, MS
White River Junction VAMC
White River Junction, Vt

RELATED LETTERS

Colorectal Cancer Risk Following a Negative Colonoscopy
Noel S. Weiss and V. Paul Doria-Rose
JAMA. 2006;296(20):2436-2437.
EXTRACT | FULL TEXT  

Colorectal Cancer Risk Following a Negative Colonoscopy—Reply
Harminder Singh, Donna Turner, Lin Xue, Laura E. Targownik, and Charles N. Bernstein
JAMA. 2006;296(20):2437-2438.
EXTRACT | FULL TEXT