Misguided precedent is not a reason to use permuted blocks.

Headache The Journal of Head and Face Pain (Impact Factor: 3.19). 07/2006; 46(7):1210-2. DOI: 10.1111/j.1526-4610.2006.00517_2.x
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    ABSTRACT: Recently a great deal of attention has been paid to conflicts of interest in medical research, and the Institute of Medicine has called for more research into this important area. One research question that has not received sufficient attention concerns the mechanisms of action by which conflicts of interest can result in biased and/or flawed research. What discretion do conflicted researchers have to sway the results one way or the other? We address this issue from the perspective of selective inertia, or an unnatural selection of research methods based on which are most likely to establish the preferred conclusions, rather than on which are most valid. In many cases it is abundantly clear that a method that is not being used in practice is superior to the one that is being used in practice, at least from the perspective of validity, and that it is only inertia, as opposed to any serious suggestion that the incumbent method is superior (or even comparable), that keeps the inferior procedure in use, to the exclusion of the superior one. By focusing on these flawed research methods we can go beyond statements of potential harm from real conflicts of interest, and can more directly assess actual (not potential) harm.
    Science and Engineering Ethics 08/2014; DOI:10.1007/s11948-014-9576-2 · 1.52 Impact Factor
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    ABSTRACT: Large multicenter acute stroke trials demand a randomization procedure with a high level of treatment allocation randomness, an effective control on overall and within-site imbalances, and a minimized time delay of study treatment caused by the randomization procedure. Driven by the randomization algorithm design of A Study of the Efficacy and Safety of Activase (Alteplase) in Patients with Mild Stroke (PRISMS) (NCT02072226), this paper compares operational and statistical properties of different randomization algorithms in local, central, and step-forward randomization settings. Results show that the step-forward randomization with block urn design provides better performances over others. If the concern on the potential time delay is not serious and a central randomization system is available, the minimization method with an imbalance control threshold and a biased coin probability could be a better choice.
    Contemporary Clinical Trials 01/2015; 41. DOI:10.1016/j.cct.2015.01.013 · 1.99 Impact Factor
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    ABSTRACT: Stratified permuted block randomization has been the dominant covariate-adaptive randomization procedure in clinical trials for several decades. Its high probability of deterministic assignment and low capacity of covariate balancing have been well recognized. The popularity of this sub-optimal method is largely due to its simplicity in implementation and the lack of better alternatives. Proposed in this paper is a two-stage covariate-adaptive randomization procedure that uses the block urn design or the big stick design in stage one to restrict the treatment imbalance within each covariate stratum, and uses the biased-coin minimization method in stage two to control imbalances in the distribution of additional covariates that are not included in the stratification algorithm. Analytical and simulation results show that the new randomization procedure significantly reduces the probability of deterministic assignments, and improve the covariate balancing capacity when compared to the traditional stratified permuted block randomization. Copyright © 2014 John Wiley & Sons, Ltd.
    Statistics in Medicine 07/2014; 33(30). DOI:10.1002/sim.6266 · 2.04 Impact Factor