Mean changes versus dichotomous definitions of improvement
1Clinical Epidemiology Research and Training Unit, Boston University Medical Center, 715 Albany Street, Boston Mass 02118, USA. jja@bu.edu
Statistical Methods in Medical Research
|March 7, 2007
Summary
Dichotomous outcome definitions, while often less powerful than continuous measures in clinical trials for chronic diseases like rheumatoid arthritis (RA) and ankylosing spondylitis (AS), can closely approximate continuous outcomes in realistic scenarios.
Area of Science:
- Clinical trial methodology
- Rheumatology outcomes research
Background:
- Clinical trials for chronic diseases often use dichotomous outcome definitions.
- Continuous outcome measures are generally expected to offer better discrimination between treatment groups.
Purpose of the Study:
- To compare the statistical power of dichotomous versus continuous outcome measures in rheumatologic clinical trials.
- To evaluate the performance of established dichotomous outcomes for rheumatoid arthritis (RA) and ankylosing spondylitis (AS).
Main Methods:
- Simulation studies using multivariate normal generated data.
- Approximation of actual clinical trial data for RA and AS patients.
- Assessment of relative power for various dichotomous and continuous outcomes.
Main Results:
- Continuous outcomes are typically more powerful than dichotomous ones.
- Well-constructed dichotomous outcomes can closely approximate the power of continuous measures.
- In some situations, dichotomous outcomes may even exceed the power of continuous outcomes based on mean change.
Conclusions:
- Dichotomous outcome definitions, when well-designed, offer a viable and sometimes powerful alternative to continuous measures in rheumatologic trials.
- The choice between dichotomous and continuous outcomes should consider clinical relevance and statistical power in specific contexts.
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