Which is better policy, to prevent colorectal cancer from arising or to detect it early once present? This question, long simmering in the background, was forced to a boil when two major US clinical practice guidelines, released within months of each other, reached opposite conclusions.

Some countries have agencies that issue single, national clinical guidelines. Examples are the National Institute for Health and Clinical Excellence (NICE) in the UK and the Institute for Quality and Efficiency in Health Care (IQWIG) in Germany. In contrast, the USA has a tradition of multiple guidelines, variously prepared by professional societies and community and healthcare organisations, as well as government agencies. This approach matches the US preference for pluralism and has some advantages, despite the confusion that competing guidelines might cause. Differences among guidelines can lead to a more robust, general discussion of what is at stake when choosing among colorectal cancer screening tests. But the differences are seldom as stark as they are for these two guidelines for colorectal cancer screening.

Guidelines by a consortium of the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer and the American College of Radiology (ACS/MSTF/ACR) distinguished between tests that primarily detect cancer …