Random allocation to intervention groups remains the best method of ensuring that the groups being compared are similar at the onset of study and of avoiding removing selection bias between groups of patients. The success of randomization depends on two interrelated processes. First, an unpredictable allocation sequence must be generated based on a random procedure. Second, strict implementation of that sequence must be secured through an assignment mechanism called allocation concealment to prevent those involved in a trial from knowing upcoming assignments. Inadequate allocation concealment can lead to clinicians scheduling patient’s assignment and compromising the unpredictable allocation sequence.
Citation： LI Jing. Allocation Concealment: Why and How?. Chinese Journal of Evidence-Based Medicine, 2004, 04(10): 714-715. doi: Copy