Analysis of randomised trials with long-term follow-up

Robert D. Herbert, Jessica Kasza, Kari Bo

Research output: Contribution to journalReview ArticleOtherpeer-review

3 Citations (Scopus)


Randomised trials with long-term follow-up can provide estimates of the long-term effects of health interventions. However, analysis of long-term outcomes in randomised trials may be complicated by problems with the administration of treatment such as non-adherence, treatment switching and co-intervention, and problems obtaining outcome measurements arising from loss to follow-up and death of participants. Methods for dealing with these issues that involve conditioning on post-randomisation variables are unsatisfactory because they may involve the comparison of non-exchangeable groups and generate estimates that do not have a valid causal interpretation. We describe approaches to analysis that potentially provide estimates of causal effects when such issues arise. Brief descriptions are provided of the use of instrumental variable and propensity score methods in trials with imperfect adherence, marginal structural models and g-estimation in trials with treatment switching, mixed longitudinal models and multiple imputation in trials with loss to follow-up, and a sensitivity analysis that can be used when trial follow-up is truncated by death or other events. Clinical trialists might consider these methods both at the design and analysis stages of randomised trials with long-term follow-up.

Original languageEnglish
Article number48
Number of pages9
JournalBMC Medical Research Methodology
Issue number1
Publication statusPublished - 29 May 2018


  • Clinical trials
  • Co-intervention
  • Long-term follow-up
  • Loss to follow-up
  • Non-compliance
  • Randomized controlled trials
  • Treatment switching

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