Document Detail

Sample size considerations for GEE analyses of three-level cluster randomized trials.
MedLine Citation:
PMID:  20070297     Owner:  NLM     Status:  MEDLINE    
Cluster randomized trials in health care may involve three instead of two levels, for instance, in trials where different interventions to improve quality of care are compared. In such trials, the intervention is implemented in health care units ("clusters") and aims at changing the behavior of health care professionals working in this unit ("subjects"), while the effects are measured at the patient level ("evaluations"). Within the generalized estimating equations approach, we derive a sample size formula that accounts for two levels of clustering: that of subjects within clusters and that of evaluations within subjects. The formula reveals that sample size is inflated, relative to a design with completely independent evaluations, by a multiplicative term that can be expressed as a product of two variance inflation factors, one that quantifies the impact of within-subject correlation of evaluations on the variance of subject-level means and the other that quantifies the impact of the correlation between subject-level means on the variance of the cluster means. Power levels as predicted by the sample size formula agreed well with the simulated power for more than 10 clusters in total, when data were analyzed using bias-corrected estimating equations for the correlation parameters in combination with the model-based covariance estimator or the sandwich estimator with a finite sample correction.
Steven Teerenstra; Bing Lu; John S Preisser; Theo van Achterberg; George F Borm
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Biometrics     Volume:  66     ISSN:  1541-0420     ISO Abbreviation:  Biometrics     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2010-12-14     Completed Date:  2011-03-31     Revised Date:  2013-05-31    
Medline Journal Info:
Nlm Unique ID:  0370625     Medline TA:  Biometrics     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1230-7     Citation Subset:  IM    
Copyright Information:
© 2010, The International Biometric Society.
Department of Epidemiology, Biostatistics and Health Technology Assessment, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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MeSH Terms
Cluster Analysis*
Health Facilities
Health Personnel
Models, Statistical
Randomized Controlled Trials as Topic / statistics & numerical data*
Sample Size
Grant Support
R01 AA016806/AA/NIAAA NIH HHS; R01 AA016806-01A1/AA/NIAAA NIH HHS; R01 AA016806-01A1/AA/NIAAA NIH HHS; R01 AA016806-02/AA/NIAAA NIH HHS; R01 AA016806-02/AA/NIAAA NIH HHS; R01 AA016806-03/AA/NIAAA NIH HHS; R01 AA016806-03/AA/NIAAA NIH HHS

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