Sample size estimation for cluster randomized controlled trials.

Cluster randomized controlled trials (cRCTs) are commonly used by clinical researchers. The advantages of cRCTs include preventing treatment contamination, enhancing administrative efficiency, convenience, external validity, ethical considerations, and likelihood of increased compliance by participants. However, when designing a cRCT, clinical researchers are faced with challenges, such as cluster units that may not have an equal number of participants within each. In this Technical Note, we discuss approaches for estimating the sample size, while taking into account unequal cluster sizes, and strategies for optimizing the design of cluster trials.

[1]  Andrew Copas,et al.  Methods for sample size determination in cluster randomized trials , 2015, International journal of epidemiology.

[2]  A. Donner,et al.  Randomization by cluster. Sample size requirements and analysis. , 1981, American journal of epidemiology.

[3]  Stephan Milosavljevic,et al.  Effectiveness of a lumbopelvic monitor and feedback device to change postural behaviour: a protocol for the ELF cluster randomised controlled trial , 2017, BMJ Open.

[4]  Karla Hemming,et al.  Sample size calculations for cluster randomised controlled trials with a fixed number of clusters , 2011, BMC medical research methodology.

[5]  David J Torgerson,et al.  Contamination in trials: is cluster randomisation the answer? , 2001, BMJ : British Medical Journal.

[6]  A. Donner,et al.  Pitfalls of and controversies in cluster randomization trials. , 2004, American journal of public health.

[7]  J H Abbott,et al.  Manual therapy, exercise therapy, or both, in addition to usual care, for osteoarthritis of the hip or knee: a randomized controlled trial. 1: clinical effectiveness. , 2013, Osteoarthritis and cartilage.

[8]  Deborah Ashby,et al.  Lessons for cluster randomized trials in the twenty-first century: a systematic review of trials in primary care , 2004, Clinical trials.

[9]  Mirjam Moerbeek,et al.  A comparison between traditional methods and multilevel regression for the analysis of multicenter intervention studies. , 2003, Journal of clinical epidemiology.

[10]  J Cornfield,et al.  Randomization by group: a formal analysis. , 1978, American journal of epidemiology.

[11]  D. Ashby,et al.  Sample size for cluster randomized trials: effect of coefficient of variation of cluster size and analysis method. , 2006, International journal of epidemiology.

[12]  Ziyad Mahfoud,et al.  What Is an Intracluster Correlation Coefficient? Crucial Concepts for Primary Care Researchers , 2004, The Annals of Family Medicine.

[13]  Allan Donner,et al.  Sample size estimation in cluster randomized trials: An evidence-based perspective , 2012, Comput. Stat. Data Anal..

[14]  J. Abbott.  The distinction between randomized clinical trials (RCTs) and preliminary feasibility and pilot studies: what they are and are not. , 2014, The Journal of orthopaedic and sports physical therapy.

[15]  Stephan Milosavljevic,et al.  The effectiveness of a lumbopelvic monitor and feedback device to change postural behavior: a feasibility randomized controlled trial. , 2014, The Journal of orthopaedic and sports physical therapy.

[16]  Neil Klar,et al.  Sample size re‐estimation in cluster randomization trials , 2002, Statistics in medicine.

[17]  Ken P. Kleinman,et al.  The Effect of Cluster Size Variability on Statistical Power in Cluster-Randomized Trials , 2015, PloS one.

[18]  Does Passive Mobilization of Shoulder Region Joints Provide Additional Benefit Over Advice and Exercise Alone for People Who Have Shoulder Pain and Minimal Movement Restriction? A Randomized Controlled Trial , 2011, Physical Therapy.

[19]  G. V. van Breukelen,et al.  Calculating sample sizes for cluster randomized trials: we can keep it simple and efficient! , 2012, Journal of clinical epidemiology.