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Clinical trials and the response rate illusion
Irving Kirsch1, Joanna Moncrieff
1Psychology, University of Hull, Hull HU6 7RX, United Kingdom. i.kirsch@hull.ac.uk
Contemporary Clinical Trials
|December 22, 2006
Summary
Analyzing clinical trial data using mean change scores versus response rates can yield different conclusions. Small improvements in scores can significantly alter response rates, potentially creating an illusion of clinical effectiveness.
Area of Science:
- Clinical research methodology
- Biostatistics
- Medical data analysis
Background:
- Clinical trial outcomes are frequently analyzed using mean change scores or response rates.
- These distinct analytical approaches can lead to conflicting interpretations of treatment efficacy.
- Understanding these discrepancies is crucial for accurate clinical trial reporting.
Purpose of the Study:
- To investigate the reasons behind divergent conclusions from mean change scores and response rates in clinical trials.
- To explore the implications of these analytical differences on the interpretation of clinical trial data.
- To critically evaluate the utility and potential pitfalls of response rates in reporting treatment effectiveness.
Main Methods:
- Comparative analysis of two common clinical trial outcome metrics: mean change scores and response rates.
- Exploration of the mathematical relationship between continuous improvement scores and dichotomous response criteria.
- Examination of how shifts in patient improvement translate to changes in calculated response rates.
Main Results:
- Minor variations in mean improvement scores can result in disproportionately large changes in calculated response rates.
- Response rates do not reflect the degree of improvement in non-responders, who may still show clinically significant gains.
- The threshold for classifying a patient as a 'responder' can obscure substantial, clinically meaningful improvements in non-responders.
Conclusions:
- Response rates can create a misleading impression of clinical effectiveness by focusing on a threshold rather than continuous improvement.
- Patients classified as non-responders may have experienced meaningful improvement and could benefit from continued treatment.
- A critical appraisal of how clinical trial data is presented is necessary to avoid misinterpretations of treatment efficacy.
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