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Published on: September 20, 2019
Design, objectives, execution and reporting of published open-label extension studies
Bowers Megan1, Ruth M Pickering, Mark Weatherall
1Public Health Sciences and Medical Statistics, School of Medicine, University of Southampton, Southampton, UK.
Journal of Evaluation in Clinical Practice
|November 3, 2010
Summary
Open-label extension studies following randomized controlled trials (RCTs) vary significantly in design and participant retention. The validity of evidence from these pharmaceutical studies requires individual assessment, as design differences and participant dropout are key concerns.
Area of Science:
- Clinical Trials
- Pharmaceutical Research
- Evidence-Based Medicine
Background:
- Open-label extension (OLE) studies are increasingly used after blinded randomized controlled trials (RCTs).
- Concerns exist regarding the regulatory compliance and evidence validity of OLE studies.
- OLE studies are often treated as a uniform group, despite design variations.
Purpose of the Study:
- To analyze the objectives, design, conduct, and reporting of published OLE studies.
- To identify common practices and variations in OLE study methodologies.
- To evaluate factors influencing the validity of evidence generated from OLE studies.
Main Methods:
- A systematic literature search of Embase and Medline databases (1996-2008) identified 268 relevant papers.
- A random sample of 50 OLE studies underwent detailed review.
- Data extraction focused on study objectives, participant allocation, and retention rates.
Main Results:
- Efficacy was a stated objective in over 80% of reviewed OLE studies.
- Common allocation methods included all participants switching to active treatment or only new drug recipients continuing.
- Participant enrollment in OLEs averaged 74% of preceding RCT participants, with a 57% completion rate.
Conclusions:
- Published OLE studies exhibit heterogeneity in design and participant retention, necessitating individual validity assessments.
- Potential bias in OLE studies may stem more from participant selection ('slippage') than from lack of blinding.
- The validity of evidence from OLE studies depends on specific design features and participant flow.
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