Table 1.

Two estimand strategies for PD trials

Attribute	Typical PD trial estimand	Alternative treatment policy estimand
Treatment	Experimental treatment or placebo added to background therapy with adjustment of the background medication permitted during the first titration period, but not thereafter	Experimental treatment or placebo added to background therapy, dosed as required, and alternative medication, dosed as required
Population	Idiopathic PD with ‘wearing off’ phenomenon	Idiopathic PD with ‘wearing off’ phenomenon
Outcome	Change from baseline in absolute OFF-time up to the end of maintenance phase	Change from baseline in absolute OFF-time up to the end of maintenance phase
Population-level summary	Mean difference	Mean difference
Postrandomisation event	Adjustment of PD medication during the maintenance period Hypothetical strategy; that is, the treatment effect in the hypothetical case where adjustment to PD medication did not occur	Adjustment of PD medication during the maintenance period Treatment policy strategy where data after the post randomisation events is collected and used in the analysis.

PD, Parkinson’s disease.