This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Vozdolska, R. Articles by Edland, S. D Search for Related Content PubMed PubMed Citation Articles by Vozdolska, R. Articles by Edland, S. D Social Bookmarking                         What's this?

The net effect of alternative allocation ratios on recruitment time and trial cost

Department of Family and Preventive Medicine, University of California San Diego, La Jolla, CA, USA

Mary Sano

Mount Sinai School of Medicine, New York, NY, USA

Paul Aisen

Department of Neuroscience, University of California San Diego, La Jolla, CA, USA

Steven D Edland

Department of Family and Preventive Medicine, University of California San Diego, La Jolla, CA, USA, Department of Neuroscience, University of California San Diego, La Jolla, CA, USA, sedland{at}ucsd.edu

Background Increasing the proportion of subjects allocated to the experimental treatment in controlled clinical trials is often advocated as a method of increasing recruitment rates and improving the performance of trials. The presumption is that the higher likelihood of randomization to the experimental treatment will be perceived by potential study enrollees as an added benefit of participation and will increase recruitment rates and speed the completion of trials. However, studies with alternative allocation ratios require a larger sample size to maintain statistical power, which may result in a net increase in time required to complete recruitment and a net increase in total trial cost.

Purpose To describe the potential net effect of alternative allocation ratios on recruitment time and trial cost.

Methods Models of recruitment time and trial cost were developed and used to compare trials with 1:1 allocation to trials with alternative allocation ratios under a range of per subject costs, per day costs, and enrollment rates.

Results In regard to time required to complete recruitment, alternative allocation ratios are net beneficial if the recruitment rate improves by more than about 4% for trials with a 1.5:1 allocation ratio and 12% for trials with a 2:1 allocation ratio. More substantial improvements in recruitment rate, 13 and 47% respectively for scenarios we considered, are required for alternative allocation to be net beneficial in terms of tangible monetary cost.

Limitations The cost models were developed expressly for trials comparing proportions or means across treatment groups.

Conclusions Using alternative allocation ratio designs to improve recruitment may or may not be time and cost-effective. Using alternative allocation for this purpose should only be considered for trial contexts where there is both clear evidence that the alternative design does improve recruitment rates and the attained time or cost efficiency justifies the added study subject burden implied by a larger sample size. Clinical Trials 2009; 6: 126—132. http://ctj.sagepub.com

Clinical Trials, Vol. 6, No. 2, 126-132 (2009)
DOI: 10.1177/1740774509103485


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?