I have seen that in RCT’s with very long follow up times the power of the study can be impacted by various factors in Herbet, Kasza, and Bø, 2018, and I was wondering if anyone has heard of comparing an RCT that has a long follow up time with a retrospective cohort study which could be designed to decrease loss of information due to follow up issues (I’m not talking about death/non- adherence or anything that could be associated with the trial, but random events such as moving out of a study population etc).
Would it be interesting to compare to see if the results were different?
Herbert, R. D., Kosza, J., and Bø, K. (2018). Analysis of randomised trials with long-term follow-up. BMC Medical Research Methodology. 18(48).