11782039

Source:http://linkedlifedata.com/resource/pubmed/id/11782039

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Predicate	Object
rdf:type	pubmed:Citation
lifeskim:mentions	umls-concept:C0025663, umls-concept:C0242618, umls-concept:C0376209, umls-concept:C0456081, umls-concept:C1707455
pubmed:issue	24
pubmed:dateCreated	2002-1-8
pubmed:abstractText	In fixed sample size designs, precise knowledge about the magnitude of the outcome variable's variance in the planning phase of a clinical trial is mandatory for an adequate sample size determination. Wittes and Brittain introduced the internal pilot study design that allows recalculation of the sample size during an ongoing trial using the estimated variance obtained from an interim analysis. However, this procedure requires the unblinding of the treatment code. Since unblinding of an ongoing trial should be avoided whenever possible, there should be some benefit of this design compared with blinded sample size recalculation procedures to justify the unveiling of the treatment code. In this paper, we compare several sample size recalculation procedures with and without unblinding. The simulation results indicate that the procedures behave similarly. In particular, breaking of the blind is not required for an efficient sample size adjustment. We also compare these pure sample size adaptation procedures with study designs which additionally allow for early stopping. Evaluation of the cumulative distribution function of the resulting sample sizes shows that the option for early stopping may lead to lower expectation but generally to a higher variability. The procedures are illustrated by an example of a trial in the treatment of depression.
pubmed:language	eng
pubmed:journal	http://linkedlifedata.com/resource/pubmed/journal/8215016
pubmed:citationSubset	IM
pubmed:status	MEDLINE
pubmed:month	Dec
pubmed:issn	0277-6715
pubmed:author	pubmed-author:FriedlMM, pubmed-author:KieserMM
pubmed:copyrightInfo	Copyright 2001 John Wiley & Sons, Ltd.
pubmed:issnType	Print
pubmed:day	30
pubmed:volume	20
pubmed:owner	NLM
pubmed:authorsComplete	Y
pubmed:pagination	3861-73
pubmed:dateRevised	2007-11-15
pubmed:meshHeading	pubmed-meshheading:11782039-Computer Simulation, pubmed-meshheading:11782039-Depression, pubmed-meshheading:11782039-Double-Blind Method, pubmed-meshheading:11782039-Humans, pubmed-meshheading:11782039-Hypericum, pubmed-meshheading:11782039-Phytotherapy, pubmed-meshheading:11782039-Randomized Controlled Trials as Topic, pubmed-meshheading:11782039-Sample Size
pubmed:year	2001
pubmed:articleTitle	A comparison of methods for adaptive sample size adjustment.
pubmed:affiliation	Medical Biometry Unit, University of Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany.
pubmed:publicationType	Journal Article, Comparative Study, Research Support, Non-U.S. Gov't