There is controversy regarding how comorbidity impacts on colorectal cancer screening, especially in the context of organised programmes. The aim of this study is to assess the effect of comorbidities on participation in the Barcelona population-based colorectal cancer screening programme (BCCSP). Cross-sectional study carried out in ten primary care centres involved in the BCCSP. Individuals aged 50 to 69, at average risk of colorectal cancer, who were invited to participate in the first round of the faecal immunochemical test-based BCCSP were included (2011–2012). The main variable was participation in the BCCSP. Comorbidity was assessed by clinical risk group status. Other adjusting variables were age, sex, socioeconomic deprivation, visits to primary care, smoking, alcohol consumption and body mass index. Logistic regression models were used to test the association between participation in the programme and potential explanatory variables. The results were given as incidence rate ratios (IRR) and their 95% confidence intervals (CI). Of the 36,208 individuals included, 17,404 (48%) participated in the BCCSP. Participation was statistically significantly higher in women, individuals aged 60 to 64, patients with intermediate socioeconomic deprivation, and patients with more medical visits. There was a higher rate of current smoking, high-risk alcohol intake, obesity and individuals in the highest comorbidity categories in the non-participation group. In the adjusted analysis, only individuals with multiple minor chronic diseases were more likely to participate in the BCCSP (IRR 1.14; 95% CI [1.06 to 1.22]; p < 0.001). In contrast, having three or more dominant chronic diseases was associated with lower participation in the screening programme (IRR 0.76; 95% CI [0.65 to 0.89]; p = 0.001). Having three or more dominant chronic diseases, was associated with lower participation in a faecal immunochemical test-based colorectal cancer screening programme, whereas individuals with multiple minor chronic diseases were more likely to participate. Further research is needed to explore comorbidity as a cause of non-participation in colorectal cancer screening programmes and which individuals could benefit most from colorectal cancer screening.

Screening with faecal occult blood tests reduces colorectal cancer-related mortality; however, age, sex and socioeconomic factors affect screening outcomes and could lead to unequal mortality benefits. The aim of this study was to describe the main outcomes of the population-based Barcelona colorectal cancer screening programme (BCRCSP) by deprivation. Retrospective study of the eligible population of the first round of the BCRCSP. Participants’ postal addresses were linked with the MEDEA database to obtain the deprivation quintiles (Dq). Chi-squared tests were used to compare proportions across variables and logistic regression was used to estimate the adjusted effects of age, sex and deprivation on uptake, FIT positivity, colonoscopy adherence and advanced neoplasia detection rate. Overall uptake was 44.7%, higher in Dq2, 3 and 4 (OR 1.251, 1.250 and 1.276, respectively) than in the least deprived quintile (Dq 1), and lowest in Dq5 (OR 0.84). Faecal immunochemical test (FIT) positivity and the percentage of people with detectable faecal haemoglobin below the positivity threshold increased with deprivation. The advanced neoplasia detection rate was highest in Dq4. Unlike most regions where inequalities are graded along the socioeconomic continuum, inequalities in the uptake of colorectal cancer screening in Spain seem to be concentrated first in the most disadvantaged group and second in the least deprived group. The correlation of deprivation with FIT-positivity and faecal haemoglobin below the positivity threshold is worrying due to its association with colorectal cancer and overall mortality.