Sample Size Adjustment in Clinical Trials for Proving Equivalence
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Sample Size Adjustment in Clinical Trials for Proving Equivalence Tim Friede and Meinhard Kieser Drug Information Journal 2001 35: 1401 DOI: 10.1177/009286150103500436 The online version of this article can be found at: http://dij.sagepub.com/content/35/4/1401
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Drug Information Journal. Vol. 35, pp. 140-1408, 2001
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SAMPLE SIZE ADJUSTMENT IN CLINICAL TRIALS FOR PROVING EQUIVALENCE TIMFRIEDE,PHD Research Associate, Department of Mathematics and Statistics, Medical Statistics Unit, Lancaster University, Lancaster. United Kingdom
MEINHARD KIESER, PHD Head Biornetrics, Dr.Willmar Schwabe Pharmaceuticals, Karlsruhe, Germany
To ovemome the problem of uncertainty in the planning phase of clinical trials, study designs have been proposed that allow for mid-course reestimation of the sample size. Using a study in asthma patients, we illustrate how blind sample size adjustment can be performed in an equivalence trial. Thereby, we demonstrate how the type I e m r rate can be controlled. Furthec we show that the well-known expectation-maximizationalgorithm-based procedure by Gould and Shih is inappropriatefor the purpose of sample size reestimation. Key Words: Interim analysis; Sample size review; Sample size adjustment; Equivalence trial; Control of the type I error rate terim analyses, the treatment effect is estimated and a hypothesis test is performed FOR BOTH ETHICAL AND economic rea- after recruitment of a certain number of pasons there is a strong need for adequate sample tients. In contrast, in a design with so-called sizes in clinical trials. In the planning phase of sample size review, nuisance parameters (eg, a study, however, there is generally a lack of variance) are estimated and no test is done. information concerning the magnitude of the As compared to the design with interim analwithin-treatment group variability, leading to ysis, the design with sample size review does a high risk of an inadequate final sample size. not offer the possibility of early-stopping In this situation,clinical trial designs that allow with rejection of the null hypothesis. for mid-course reestimation of the sample size An example of a design with interim analare a welcome solution. ysis is the adaptive procedure proposed by Several study designs with sample size Bauer and Kohne (1). Wittes and Brittain adjustment have been proposed; they can be (2)
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