Randomization in clinical trials: Conclusions and recommendations

Abstract

The statistical properties of simple (complete) randomization, permuted-block (or simply blocked) randomization, and the urn adaptive biased-coin randomization are summarized. These procedures are contrasted to covariate adaptive procedures such as minimization and to response adaptive procedures such as the play-the-winner rule. General recommendations are offered regarding the use of complete, permuted-block, or urn randomization. In a large double-masked trial, any of these procedures may be acceptable. For a given trial, the relative merits of each procedure should be carefully weighed in relation to the characteristics of the trial. Important considerations are the size of the trial, overall as well as within the smallest subgroup to be employed in a subgroup-specific analysis, whether or not the trial is to be masked, and the resources needed to perform the proper randomization-based permutational analysis.

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“…The low risk subjects (n=54) did not receive any early intervention. These three groups were carefully matched for age, gender, race, and time since original injury based upon an urn randomization procedure (12,13). There was no cost to patients assigned to the early intervention group.…”

A randomized clinical trial to determine the effect of angiotensin inhibitors reduction on creatinine clearance and haemoglobin in heart failure patients with chronic kidney disease and anaemia

“…In order to balance the group sizes, a restricted randomization protocol was used [20]. Blocked randomization was used with a block size of six and an allocation ratio of 2 : 1 (four subjects to one group and two to the other), with a total of eight blocks.…”

When staff handle Staph

“…A randomized controlled trial (RCT) would be the best way to evaluate whether implementation of the website in daily work practice is truly effective in this regard. However, conducting an RCT to measure the influence of website use on behavior change is a great challenge, for the reason that use of a website is hard to control next to the general drawbacks inherent to RCTS such are their long duration and the high costs (Lachin et al, 1988). Furthermore, recent reanalyses have brought the results from observational and randomized studies into line.…”