Association of socioeconomic status and receipt of colorectal cancer investigations: a population-based retrospective cohort study.

BACKGROUND: Although the Canadian health care system was designed to ensure equal access, inequities persist. It is not known if inequities exist for receipt of investigations used to screen for colorectal cancer (CRC). We examined the association between socioeconomic status and receipt of colorectal investigation in Ontario.
METHODS: People aged 50 to 70 years living in Ontario on Jan. 1, 1997, who did not have a history of CRC, inflammatory bowel disease or colorectal investigation within the previous 5 years were followed until death or Dec. 31, 2001. Receipt of any colorectal investigation between 1997 and 2001 inclusive was determined by means of linked administrative databases. Income was imputed as the mean household income of the person's census enumeration area. Multivariate analysis was performed to evaluate the relationship between the receipt of any colorectal investigation and income.
RESULTS: Of the study cohort of 1,664,188 people, 21.2% received a colorectal investigation in 1997-2001. Multivariate analysis demonstrated a significant association between receipt of any colorectal investigation and income (p < 0.001); people in the highest-income quintile had higher odds of receiving any colorectal investigation (adjusted odds ratio [OR] 1.38; 95% confidence interval [CI] 1.36-1.40) and of receiving colonoscopy (adjusted OR 1.50; 95% CI 1.48-1.53).
INTERPRETATION: Socioeconomic status is associated with receipt of colorectal investigations in Ontario. Only one-fifth of people in the screening-eligible age group received any colorectal investigation. Further work is needed to determine the reason for this low rate and to explore whether it affects CRC mortality.