Partially clustered designs for clinical trials: Unifying existing designs using consistent terminology

Area of Science:

• Clinical Trials Methodology
• Biostatistics
• Epidemiology

Background:

• Standard clinical trial designs assume independent observations, while clustered designs account for correlated outcomes within groups.
• Partially clustered trials, where only a subset of observational units belong to a cluster, are common in fields like neonatology and ophthalmology but lack standardized terminology and methodology.
• Existing literature has limited attention on partially clustered data, hindering the development and dissemination of appropriate design and analysis methods.

Approach:

• This article proposes an overarching definition for partially clustered trials, unifying existing designs such as group-based treatments and facilitator effects.
• Four distinct types of partially clustered trial designs are defined, based on the timing of clustering (pre- or post-randomization) and randomization methods for clustered observations.
• The study reviews published reports of partially clustered trials to assess current reporting practices and identify inconsistencies.

Key Points:

• Partially clustered trials are prevalent across various medical fields, including neonatology, ophthalmology, and group-based interventions.
• Inconsistent terminology and incomplete descriptions in published reports make it difficult to identify and analyze these trials.
• The proposed definitions and terminology aim to standardize the reporting of partially clustered trials.

Conclusions:

• Adopting the presented definitions and terminology can significantly enhance the reporting of partially clustered trials.
• Increased awareness and standardized reporting will encourage further methodological research into the design and analysis of these complex trial types.
• Ultimately, improving the understanding and application of partially clustered trial designs will enhance the overall quality of clinical research.