Extension Reports in Clinical Trials: A Systematic Review and Consequent Guidance

Area of Science:

• Cardiology
• Clinical Trials
• Medical Research Methodology

Background:

• Long-term efficacy and safety of cardiovascular interventions often remain unclear after initial trial publication.
• Sequel publications with extended follow-up are common, but standardized reporting guidelines are lacking.

Purpose of the Study:

• To assess the characteristics of extension reports for cardiovascular trials.
• To identify common practices and potential issues in reporting extended follow-up data.

Main Methods:

• Systematic search of MEDLINE for cardiovascular trial extension papers published between January 2019 and October 2023 in 7 high-impact journals.
• Screening of 1,388 papers, with data extraction from 69 identified extension reports.

Main Results:

• 69 extension reports from 64 trials were identified, covering various cardiovascular topics, most commonly coronary heart disease.
• Significant diversity in follow-up duration, outcome reporting, and methodology (e.g., treatment crossovers, non-standard analyses) was observed.
• Many extension studies lacked prespecification, dedicated protocols, or multiplicity corrections, and some reported considerable loss to follow-up.

Conclusions:

• This systematic investigation revealed considerable diversity in the reporting of cardiovascular trial extension studies.
• Several methodological and reporting issues require greater attention to ensure the validity and interpretation of extended follow-up data.
• Recommendations are provided for planning, conducting, and reporting future extension studies.