Determinants of non-participation in colon examination following positive stool sample in colorectal cancer screening

Background: Social inequalities has been shown for participation in colorectal cancer screening and recently in the initial stool sample blood test. If these differences persist at follow-up colon examination after a positive stool test, it would suggest that social inequality in screening may be greater than the inequality observed in initial stool sample blood test. Methods: All data were derived from national registers. Using logistic regression analyses, odds of non-participation for follow-up colon examination were estimated based on age group, educational level, income quartile, immigration status and marital status in men and in women, who had participated in initial stool sample test for blood with a positive result. Results: Among 20 849 men and 16 565 women invited for follow-up colonoscopy in the period 2014-15, 10.63 and 11.37%, respectively, did not attend. In men, odds of non-participation were higher in the eldest, those with lower income and lower educational level, in immigrants and in singles. Odds ratio (OR) in males of highest income quartile was 0.54 [95% confidence interval (CI) 0.46; 0.63] compared with lowest income quartile. In women, the differences were not as large. OR in females of highest income quartile was 0.73 (95% CI 0.61; 0.87) compared with lowest income quartile. Conclusion: Sociodemographic differences in odds of non-participation exist in follow-up colon examination in the Danish colorectal cancer screening. Differences were evident in all subgroups of the male population. The same patterns were seen in women. Social inequalities in participation for follow-up colon examination can increase overall social inequality and consequently, lead to health disparities.