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Improved adherence adjustment in the Coronary Drug Project
Eleanor J Murray1, Miguel A Hernán2,3,4
1Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Suite 911, Boston, MA, 02115, USA. emurray@mail.harvard.edu.
Trials
|March 7, 2018
Summary
Adherence adjustment in clinical trials is possible. This study shows that accounting for adherence to placebo in the Coronary Drug Project removes the apparent link between adherence and mortality.
Area of Science:
- Clinical Trials Methodology
- Biostatistics
- Epidemiology
Background:
- The Coronary Drug Project (CDP) placebo arm data has been used to argue against adherence adjustment in randomized trials.
- Previous work demonstrated that simple adherence adjustment in the CDP is valid.
- This study re-analyzes CDP data using advanced methodological developments.
Purpose of the Study:
- To re-evaluate the possibility of valid adherence adjustment in the Coronary Drug Project using sophisticated statistical methods.
- To demonstrate that adherence to placebo can be appropriately adjusted for in randomized controlled trials.
Main Methods:
- Utilized inverse-probability weighted hazards models.
- Estimated 5-year survival and mortality risk for continuous adherence (≥80%) versus non-adherence (<80%) in the CDP placebo group.
- Adjusted for post-randomization covariates that predict adherence.
Main Results:
- The 5-year mortality risk difference estimates, after adjustment, ranged from -0.7 to 4.5 percentage points.
- Confidence intervals for these estimates were wide, indicating uncertainty but not ruling out a null effect.
Conclusions:
- Appropriate adjustment for post-randomization predictors of adherence significantly diminishes the observed association between placebo adherence and mortality in the CDP.
- This supports the potential for valid adherence adjustment in randomized trials, challenging the exclusive reliance on intention-to-treat analyses.
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