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:
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- 1. ［1］Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias: dimensions of methodological quality associated with estimates of effects in controlled trials[J]. JAMA, 1995; 273(5):408-412.
- 2. ［2］Torgerson DJ, Roberts C. Understanding controlled trials: randomization methods: concealment[J]. BMJ, 1999; 319(7 206):375-356.
- 3. ［3］Schulz, Kenneth F. Subverting randomization in controlled trials[J]. JAMA, 1995; 274(18):1 456-1 458.
- 4. ［4］Altman DG, Schulz KF. Statistics Notes: Concealing treatment allocation in randomized trials[J]. BMJ, 2001; 323(7 310):446-447.
- 5. ［5］Schulz KF, Chalmers I, Grimes DA, Altman DG. Assessing the quality of randomization from reports of controlled trials published in obstetrics and gynecology journals[J]. JAMA, 1994; 272(2):125-128.
