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Abstract:
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Target trials are RCTs one would like to conduct but cannot for ethical, financial, and/or logistical reasons. As a consequence, we must emulate such trials from observational data. A novel aspect of target trial methodology is that, for purposes of data analysis, each subject in the observational study is ‘enrolled’ in all target trials for which the subject is eligible, instead of a single trial. I will compare the strengths and weakness of the target trial approach with alternative methods for estimation of causal effects from longitudinal data with time varying confounders: structural nested models, dynamic marginal structural models, and history adjusted marginal structural models. Finally , through empirical examples, I will examine the over-arching question: Are these methodologies sufficiently reliable for their substantive results to guide clinical practice.
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