title: Sample size calculation for multicenter randomized trial: taking the center effect into account.
abstract: In multicenter trials, data from the same center are more similar than those from different centers. These similarities induce a correlation between data, known as the center effect, which is assessed by the intraclass correlation coefficient (ICC). Here, we derive a sample size formula for continuous data that takes into account this center effect. Our analytical developments lead to an elementary formula different from the classical one by a (1-rho) factor, where rho is the ICC. This work allows for adjusting and reducing the sample size according to the magnitude of the center effect and leads to a better consistency in the conduct of multicenter randomized trials.
authors.affiliation: INSERM CIC 202, Université François Rabelais, Tours, CHRU de Tours, France. emilie.vierron@med.univ-tours.fr
authors.forename: Emilie
authors.initials: E
authors.lastname: Vierron
authors.forename: Bruno
authors.initials: B
authors.lastname: Giraudeau
mesh_terms: D006801:Humans; D015233:Models, Statistical; D015337:Multicenter Studies as Topic / Q000706:statistics & numerical data*; D018579:Patient Selection; D016012:Poisson Distribution; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D012044:Regression Analysis; D018401:Sample Size