Understanding non-compliance to colorectal cancer screening: a case control study, nested in a randomised trial [ISRCTN83029072]

Background: The major limit to colorectal cancer screening effectiveness is often lowcompliance. We studied the reasons for non compliance and determinants of compliance to faecal occult blood tests in Lazio, Italy. Methods: This is a case-control study nested within a trial that tested the effect of type of test and provider on colorectal cancer screening compliance. Non compliant trial subjects were classified as cases, and compliant subjects were classified as controls. We sampled 600 cases and 600 controls matched by their general practitioner, half were invited for screening at the hospital, and the other half directly at their general practitioner's office. Cases and controls answered questions on: distance from test provider, logistical problems, perception of colorectal cancer risk, confidence in screening efficacy, fear of results, presence of colorectal cancer in the family, and gastrointestinal symptoms. Results: About 31% of cases never received the letter offering free screening, and 17% of the sampled population had already been screened. The first reported reason for non-compliance was "lack of time" (30%); the major determinant of compliance was the distance from the test provider: odds ratio > 30 minutes vs < 15 minutes 0.3 (95% CI = 0.2 - 0.7). The odds ratio for lack of time was 0.16 (95% IC 0.1 - 0.26). The effect was stronger if the hospital (0.03 95% CI = 0.01 - 0.1) rather than the general practitioner (0.3 95% CI = 0.2 - 0.6) was the provider. Twenty-two percent of controls were accompanied by someone to the test. Conclusion: To increase compliance, screening programmes must involve test providers who are geographically close to the target population.