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Challenges in Small Sample Size Cluster Trials for Medication Adherence: Insights From TAKE-IT-TOO
Spencer W Riddell1,2, Robert Platt3,4, Mary Amanda Dew5,6,7,8
1Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA.
Pediatric Transplantation
|December 22, 2025
Summary
Designing cluster randomized controlled trials (CRTs) for medication adherence in pediatric kidney transplant recipients requires careful planning. The TAKE-IT-TOO pilot study explored methods to estimate sample size needs for future CRTs, finding repeated measures enhance efficiency.
Area of Science:
- Clinical Trials Methodology
- Pediatric Nephrology
- Health Services Research
Background:
- Cluster randomized controlled trials (CRTs) are essential for evaluating interventions involving clinical teams.
- CRTs often need larger sample sizes due to within-cluster correlation and between-cluster variability.
- Accurate sample size estimation is critical for the successful design of CRTs.
Purpose of the Study:
- To estimate the intraclass correlation (ICC) for designing a full-scale CRT to improve medication adherence in pediatric kidney transplant recipients.
- To assess how different approaches to summarizing electronically measured adherence data impact ICC estimation and sample size requirements.
- To evaluate the efficiency of using repeated adherence measures versus single summary measures in CRTs.
Main Methods:
- The TAKE-IT-TOO pilot study randomized seven centers to either an adherence-promoting or healthy-living intervention.
- Medication adherence was tracked using electronic pillboxes over a 4-week run-in and 10-week intervention period.
- Generalized linear mixed models (GLMM) were used to calculate variance estimates and derive ICC values, comparing two adherence data summarization methods.
Main Results:
- Using repeated adherence measures within participants improved statistical power compared to a single summary measure.
- Estimating ICC precisely was challenging due to large standard errors around variance estimates.
- A plausible range of ICC values and corresponding sample size requirements for future trials were identified.
Conclusions:
- The TAKE-IT-TOO study highlights challenges in conducting CRTs in small populations, particularly in estimating ICC.
- Repeated outcome measures are valuable for maximizing statistical efficiency in adherence research for pediatric kidney transplant recipients.
- The findings provide guidance for designing future large-scale CRTs for medication adherence interventions in this population.
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