Statistical methods
REGRESSION, SECONDARY
All randomised participants who did not withdraw their data were included in the primary analysis. Those who died before the 12 months’ follow-up were excluded for the primary outcome, but their survey responses for secondary outcomes are included in the study. For the primary outcome, logistic regression was used to estimate the odds ratio (OR). A generalised linear model was used with the identity link function and binomial family to estimate the absolute difference in the proportion of risk-appropriate screening between groups. All regression models included the randomisation stratification factor of general practice as a fixed effect. The absolute (between-group difference in the proportions) and relative (OR) estimated effect sizes are presented with their respective 95% confidence interval (CI), and the Comparisons between groups on continuous secondary outcomes used a linear mixed-effects model that included trial group, general practice, and time (baseline, 1, 6, and 12 months) as fixed effects and individuals as random effects, with two-way interactions between group and time, except for baseline where study group means were constrained to be equal. Comparisons between groups on binary secondary endpoints with repeated outcome measures were performed using logistic regression, using generalised estimating equations with robust standard errors, with general practice as the covariate.Based on review of the blinded data, the trial steering committee agreed to conduct an explanatory analysis using a statistical test for interaction to examine if the intervention effect was modified by whether participants were due CRC screening during follow-up.Costs for delivering the intervention and associated with screening utilisation were expressed as the mean expenditure and associated 95% CI for iFOBT and colonoscopy over the period of the trial for each group, including overscreening. The cost per appropriately screened individual was calculated for the CRISP intervention compared with usual care based on the primary outcome measure and for those due screening at baseline.