To the Editor To inform the recently updated guidelines from the US Preventive Services Task Force (USPSTF) on colorectal cancer (CRC) screening,1 Dr Lin and colleagues conducted a meta-analysis of randomized trials of different screening interventions, including flexible sigmoidoscopy.2 Unfortunately, the authors pooled different age groups in the Norwegian Colorectal Cancer Prevention Trial (NORCCAP)3 to calculate the summary mortality estimate for flexible sigmoidoscopy screening. Methodologically, we do not think this approach is correct because pooling the age groups introduced confounding by age.
Holme Ø, Hoff G, Løberg M. Colorectal Cancer Screening. JAMA. 2016;316(16):1714. doi:10.1001/jama.2016.13846