替代分配比例对招募时间和试验成本的净效应。
The net effect of alternative allocation ratios on recruitment time and trial cost.
作者信息
Vozdolska Ralitza, Sano Mary, Aisen Paul, Edland Steven D
机构信息
Department of Family and Preventive Medicine, University of California San Diego, La Jolla, CA 92093-0949, USA.
出版信息
Clin Trials. 2009 Apr;6(2):126-32. doi: 10.1177/1740774509103485.
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.
背景
在对照临床试验中增加分配到实验性治疗组的受试者比例，常被视为提高招募率和改善试验效能的一种方法。其假定是，潜在的研究参与者会认为随机分配到实验性治疗组的可能性更高是参与试验的一项额外益处，这将提高招募率并加快试验完成速度。然而，采用其他分配比例的研究需要更大的样本量来维持统计效能，这可能导致完成招募所需时间的净增加以及试验总成本的净增加。
目的
描述其他分配比例对招募时间和试验成本的潜在净效应。
方法
建立招募时间和试验成本模型，并用于比较在一系列每位受试者成本、每日成本和入组率条件下，1:1分配的试验与采用其他分配比例的试验。
结果
关于完成招募所需的时间，如果采用1.5:1分配比例的试验招募率提高超过约4%，采用2:1分配比例的试验招募率提高12%，那么其他分配比例在净效应上是有益的。就实际货币成本而言，我们所考虑的情形中分别需要招募率有更显著的提高，即13%和47%，其他分配比例才在净效应上是有益的。
局限性
成本模型是专门为比较各治疗组比例或均值的试验而建立的。
结论
采用其他分配比例设计来改善招募可能具有时间和成本效益，也可能不具有。仅当有明确证据表明其他设计确实能提高招募率，且所获得的时间或成本效率足以证明因更大样本量而增加的研究受试者负担合理时，才应考虑为此目的采用其他分配比例。
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