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Transparent reporting of group-based trajectory modeling to study medication adherence: Practical considerations and
John G Rizk1, Danya M Qato1,2
1Department of Practice, Sciences, and Health Outcomes Research, University of Maryland School of Pharmacy, Baltimore.
Journal of Managed Care & Specialty Pharmacy
|March 26, 2026
Summary
Group-based trajectory modeling (GBTM) analyzes medication adherence patterns over time. This guide helps researchers use GBTM effectively, improving the quality of adherence studies.
Area of Science:
- Health Services Research
- Biostatistics
- Pharmaceutical Sciences
Background:
- Medication adherence is crucial for treatment effectiveness but often measured statically, masking dynamic changes.
- Group-based trajectory modeling (GBTM) offers a dynamic approach to understanding longitudinal medication adherence patterns.
- GBTM identifies distinct patient subgroups based on their adherence behaviors over time.
Purpose of the Study:
- To provide practical guidance on applying Group-based trajectory modeling (GBTM) for medication adherence research.
- To highlight common modeling decisions and their implications for reproducibility and interpretation.
- To identify and mitigate potential biases in GBTM studies of medication adherence.
Main Methods:
- The article reviews common methodological choices in GBTM for adherence studies, including time scale, adherence measure type (binary/continuous), and trajectory number/shape.
- It discusses practical considerations such as enrollment criteria and their impact on selection bias.
- Potential threats to validity, including immortal time bias and reverse causality, are examined.
Main Results:
- GBTM allows for a nuanced understanding of medication adherence dynamics and patient stratification.
- Careful consideration of modeling decisions and potential biases is essential for valid and reproducible results.
- Standardized reporting of GBTM components is recommended to enhance transparency.
Conclusions:
- This viewpoint provides essential guidance for researchers, clinicians, and editors utilizing GBTM in medication adherence research.
- Adopting best practices in GBTM application and reporting will strengthen the evidence base for medication adherence interventions.
- Improved methodological rigor in GBTM studies will lead to more reliable insights into patient adherence behaviors.
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