Calculation of sample size for stroke trials assessing functional outcome: comparison of binary and ordinal approaches

International Journal of Stroke : Official Journal of the International Stroke Society
Optimising Analysis of Stroke Trials Collaboration

Abstract

Many acute stroke trials have given neutral results. Sub-optimal statistical analyses may be failing to detect efficacy. Methods which take account of the ordinal nature of functional outcome data are more efficient. We compare sample size calculations for dichotomous and ordinal outcomes for use in stroke trials. Data from stroke trials studying the effects of interventions known to positively or negatively alter functional outcome--Rankin Scale and Barthel Index--were assessed. Sample size was calculated using comparisons of proportions, means, medians (according to Payne), and ordinal data (according to Whitehead). The sample sizes gained from each method were compared using Friedman 2 way ANOVA. Fifty-five comparisons (54 173 patients) of active vs. control treatment were assessed. Estimated sample sizes differed significantly depending on the method of calculation (P<0.0001). The ordering of the methods showed that the ordinal method of Whitehead and comparison of means produced significantly lower sample sizes than the other methods. The ordinal data method on average reduced sample size by 28% (inter-quartile range 14-53%) compared with the comparison of proportions; however, a 22% increase in sample size was seen with t...Continue Reading

References

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Aug 11, 2007·Stroke; a Journal of Cerebral Circulation·Stephan A Mayer

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Citations

Apr 3, 2010·Stroke; a Journal of Cerebral Circulation·Jeffrey L SaverUNKNOWN FAST-MAG Investigators and Coordinators
Mar 16, 2012·Chinese Medicine·Ana Paula S Fragoso, Arthur S Ferreira
Nov 9, 2010·Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine·Gavin D PerkinsUNKNOWN PARAMEDIC trial collaborators
Sep 22, 2010·Journal of the Neurological Sciences·Sandeep AnkolekarPhilip M W Bath
Jul 22, 2014·International Journal of Stroke : Official Journal of the International Stroke Society·Philip M BathThomas Truelsen
Sep 10, 2014·International Journal of Stroke : Official Journal of the International Stroke Society·Leonid ChurilovGeoffrey A Donnan
Mar 5, 2014·International Journal of Stroke : Official Journal of the International Stroke Society·Philip M W BathUNKNOWN ENOS Trialists
Feb 25, 2009·International Journal of Stroke : Official Journal of the International Stroke Society·Philip M W Bath, Laura J Gray
Jun 8, 2011·International Journal of Stroke : Official Journal of the International Stroke Society·UNKNOWN Optimising the Analysis of Stroke Trials Collaboration with the Writing CommitteeStuart Pocock
Feb 3, 2015·International Journal of Stroke : Official Journal of the International Stroke Society·Philip M W BathUNKNOWN TARDIS Trialists
Jul 28, 2013·CPT: Pharmacometrics & Systems Pharmacology·K E KarlssonM O Karlsson
Mar 5, 2011·Stroke; a Journal of Cerebral Circulation·Terence J QuinnDavid J Stott
Jul 19, 2008·Stroke; a Journal of Cerebral Circulation·Philip M W BathLaura J Gray
Apr 11, 2009·Stroke; a Journal of Cerebral Circulation·Anthony G Rudd, Linda S Williams
Mar 20, 2012·Stroke; a Journal of Cerebral Circulation·Philip M W BathUNKNOWN European Stroke Organisation Outcomes Working Group
Jan 24, 2009·Stroke; a Journal of Cerebral Circulation·UNKNOWN Optimising the Analysis of Stroke Trials (OAST) CollaborationTimothy Collier
May 14, 2011·Stroke; a Journal of Cerebral Circulation·Ashfaq ShuaibUNKNOWN SENTIS Trial Investigators
Dec 26, 2009·Stroke; a Journal of Cerebral Circulation·Erik CoboAntoni Dàvalos
Oct 21, 2018·Neurology·Aravind GaneshUNKNOWN Oxford Vascular Study
Feb 8, 2021·Resuscitation·J BierensG D Perkins

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Software Mentioned

Stata
OAST
GenStat
SAS

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