When recommending screening tests for colorectal cancer (CRC), the relationship between adherence to retesting and test effectiveness must be carefully considered. The important practical issue is whether an annual fecal occult blood test (FOBT) should continue to be recommended in current US guidelines without further qualification, when it has been known for decades that adherence to a program of annual FOBT testing is low, resulting in poor effectiveness of the overall screening strategy.1,2 There is a direct, positive relationship between programmatic adherence and effectiveness, such that higher retesting adherence results in greater effectiveness. For example, a 50% increase in adherence is estimated to be related to a proportionate increase in life-years gained,3 thereby elevating this test to a level that would make it a viable alternative to screening colonoscopy for patients not choosing to undergo a more invasive test.
Winawer SJ, Fischer SE, Levin B. Evidence-Based, Reality-Driven Colorectal Cancer Screening GuidelinesThe Critical Relationship of Adherence to Effectiveness. JAMA. 2016;315(19):2065-2066. doi:10.1001/jama.2016.3377