Cluster randomized trials in general (family) practice research.

Area of Science:

• General Practice
• Family Medicine
• Health Services Research

Background:

• Cluster randomized trials are increasingly utilized in general practice settings.
• These trials share similarities and differences with those conducted in education, health promotion, and public health.

Purpose of the Study:

• To discuss the design and analysis of cluster randomized trials in general practice.
• To address key issues including intra-cluster correlation, sample size determination, and varying cluster sizes.
• To consider ethical aspects and the principle of intention to treat.

Main Methods:

• Review of design and analysis considerations for cluster randomized trials.
• Discussion on estimation and range of intra-cluster correlation coefficients in general practice.
• Exploration of challenges related to varying numbers of subjects per cluster.
• Consideration of ethical issues and the intention-to-treat principle.

Main Results:

• Identified challenges in sample size estimation due to intra-cluster correlation.
• Highlighted difficulties in planning and analysis arising from unequal cluster sizes.
• Provided an example of analysis for continuous outcomes.
• Summarized available software for trial analysis.

Conclusions:

• Effective design and analysis of cluster randomized trials in general practice require careful consideration of specific issues.
• Addressing intra-cluster correlation and cluster size variability is crucial for accurate sample size calculation and robust analysis.
• Ethical considerations and adherence to principles like intention to treat are vital for trial integrity.