Letters Section Editor: Robert M. Golub, MD, Senior Editor.
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).
Robertson DJ, Sirovich BE. Colorectal Cancer Risk Following a Negative Colonoscopy. JAMA. 2006;296(20):2436-2438. doi:10.1001/jama.296.20.2437-a