Haahr Mette Thorlund, Hróbjartsson Asbjørn
The Nordic Cochrane Centre, Rigshospitalet, Copenhagen, Denmark.
Clin Trials. 2006;3(4):360-5. doi: 10.1177/1740774506069153.
Insufficient blinding of persons involved in randomized clinical trials is associated with bias. The appraisal of the risk of bias is difficult without adequate information in trial reports.
We wanted to study how blinding is reported in clinical trials and how lack of reporting relate to lack of blinding.
A cohort study of 200 blinded randomized clinical trials published in 2001 randomly sampled from the Cochrane Central Register of Controlled Trials, and a questionnaire survey of the trial authors.
One-hundred and fifty-six (78%) articles described trials as 'double blind'. In three (2%) of such articles the blinding status of patients, health care providers and data collectors was explicitly described. Eighty-eight (56%) articles did not describe the blinding status of any trial person, and 41 articles (26%) reported no blinding relevant information at all beyond the trial being 'double blind'. One-hundred and thirty (65%) surveyed authors responded. Patients were blinded in 101 (97%) 'double blind' trials, and health care providers in 93 (89%). Twenty (19%) 'double blind' trials had not blinded either patients, health care providers or data collectors. Survey responders provided 15 different operational meanings of the term 'double blind', and typically felt that their preferred definition was the most widely used.
The proportions in the author survey may be too optimistic due to reporting bias. It is not known how the increased use of the CONSORT guidelines may have affected reporting in years after 2001.
The blinding status of key trial persons was incompletely reported in most randomized clinical trials. Unreported blinding may be frequent, but one of five 'double blind' trials did not blind either patients, treatment providers or data collectors. Authors, referees, and journal editors could improve the completeness of reporting of blinding, eg, by adhering to the CONSORT statement. It is inappropriate to presume blinding of key trial persons based only on the ambiguous term 'double blind'.
参与随机临床试验的人员设盲不充分会导致偏差。若无试验报告中的充分信息，对偏差风险的评估会很困难。
我们想研究临床试验中设盲情况是如何报告的，以及报告缺失与未设盲之间的关系。
从Cochrane对照试验中央注册库中随机抽取2001年发表的200项设盲随机临床试验进行队列研究，并对试验作者进行问卷调查。
156篇（78%）文章将试验描述为“双盲”。在其中3篇（2%）此类文章中，明确描述了患者、医疗服务提供者和数据收集者的设盲状态。88篇（56%）文章未描述任何试验人员的设盲状态，41篇（26%）文章除了试验为“双盲”外，未报告任何与设盲相关的信息。130名（65%）接受调查的作者回复了问卷。在101项（97%）“双盲”试验中患者被设盲，93项（89%）中医疗服务提供者被设盲。20项（19%）“双盲”试验中患者、医疗服务提供者或数据收集者均未被设盲。接受调查的回复者给出了“双盲”一词的15种不同操作定义，且通常认为他们偏爱的定义是使用最广泛的。
由于报告偏差，作者调查中的比例可能过于乐观。尚不清楚CONSORT指南使用的增加在2001年之后的年份里对报告有何影响。
在大多数随机临床试验中，关键试验人员的设盲状态报告不完整。未报告设盲情况可能很常见，但五分之一的“双盲”试验中患者、治疗提供者或数据收集者均未被设盲。作者、评审人员和期刊编辑可以通过遵循CONSORT声明等方式提高设盲报告的完整性。仅根据模糊的“双盲”一词假定关键试验人员被设盲是不合适的。
