RESUMEN
The success of fecal occult blood-based colorectal cancer screening programs is dependent on repeating screening at short intervals (ie, every 1-2 years). We conducted a literature review to assess measures that have been used to assess longitudinal adherence to fecal-based screening. Among 46 citations identified and included in this review, six broad classifications of longitudinal adherence were identified: (a) stratified single-round attendance, (b) all possible adherence permutations, (c) consistent/inconsistent/never attendance, (d) number of times attended, (e) program adherence and (f) proportion of time covered. Advantages and disadvantages of these measures are described, and recommendations on which measures to use based on data availability and scientific question are also given. Stratified single round attendance is particularly useful for describing the yield of screening, while programmatic adherence measures are best suited to evaluating screening efficacy. We recommend that screening programs collect detailed longitudinal, individual-level data, not only for the screening tests themselves but additionally for diagnostic follow-up and surveillance exams, to allow for maximum flexibility in reporting adherence patterns using the measure of choice.