Alternative approaches to assessing intervention effectiveness in randomized trials: application in a colorectal cancer screening study

Previous analysis of a randomized community-based trial of a multi-component intervention to increase colorectal cancer (CRC) screening among Filipino Americans (n = 548) found significantly higher screening rates in the two intervention groups compared to the control group, when using intent-to-treat analysis and self-reported screening as the outcome. This report describes more nuanced findings obtained from alternative approaches to assessing intervention effectiveness to inform future intervention implementation. The effect of the intervention on CRC screening receipt during follow-up was estimated using methods that adjusted for biases due to missing data and self-report and for different combinations of intervention components. Adjustment for self-report used data from a validation substudy. Effectiveness within demographic subgroups was also examined. Analyses accounting for self-report bias and missing data supported the effectiveness of the intervention. The intervention was also broadly effective across the demographic characteristics of the sample. Estimates of the intervention effect were highest among participants whose providers received a letter as part of the intervention. The findings increase confidence that the intervention could be broadly effective at increasing CRC screening in this population. Subgroup analyses and attempts to deconstruct multi-component interventions can provide important information for future intervention development, implementation, and dissemination.