Only 6 (8%) RCTs had adequate allocation concealment, with 5 RCTs using sealed opaque envelopes and 1 RCT using centralized computer allocation.

• 仅有6篇（8.；11%25）分配方案隐藏充分，其中5篇采用密封不透光的信封，1篇采用中心随机分组；