BACKGROUND Blinding aims to minimize biases from what participants and investigators know or believe. Randomized controlled trials, despite being the gold standard to evaluate treatment effect, do not generally assess the success of blinding. We investigated the extent of blinding in back pain trials and the associations between participant guesses and treatment effects. METHODS We did a review with PubMed/OvidMedline, 2000-2019. Eligibility criteria were back pain trials with data available on treatment effect and participants' guess of treatment. For blinding, blinding index was used as chance-corrected measure of excessive correct guess (0 for random guess). For treatment effects, within- or between-arm effect sizes were used. Analyses of investigators' guess/blinding or by treatment modality were performed exploratorily. RESULTS Forty trials (3899 participants) were included. Active and sham treatment groups had mean blinding index of 0.26 (95% confidence interval: 0.12, 0.41) and 0.01 (-0.11, 0.14), respectively, meaning 26% of participants in active treatment believed they received active treatment, whereas only 1% in sham believed they received sham treatment, beyond chance, that is, random guess. A greater belief of receiving active treatment was associated with a larger within-arm effect size in both arms, and ideal blinding (namely, "random guess," and "wishful thinking" that signifies both groups believing they received active treatment) showed smaller effect sizes, with correlation of effect size and summary blinding indexes of 0.35 (p = 0.028) for between-arm comparison. We observed uniformly large sham treatment effects for all modalities, and larger correlation for investigator's (un)blinding, 0.53 (p = 0.046). CONCLUSION Participants in active treatments in back pain trials guessed treatment identity more correctly, while those in sham treatments tended to display successful blinding. Excessive correct guesses (that could reflect weaker blinding and/or noticeable effects) by participants and investigators demonstrated larger effect sizes. Blinding and sham treatment effects on back pain need due consideration in individual trials and meta-analyses.

中文翻译：

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2000-2019 年背痛随机对照试验的盲法、假手术和治疗效果：回顾和荟萃分析方法


背景 盲法旨在最大限度地减少参与者和调查人员所知或所信的偏差。随机对照试验尽管是评估治疗效果的金标准，但通常不评估盲法的成功与否。我们调查了背痛试验中的盲法程度以及参与者的猜测与治疗效果之间的关联。方法 我们对 2000-2019 年 PubMed/OvidMedline 进行了回顾。资格标准是背痛试验，并提供治疗效果和参与者对治疗的猜测的数据。对于盲法，盲法指数被用作过度正确猜测的机会校正度量（0 表示随机猜测）。对于治疗效果，使用臂内或臂间效应大小。探索性地对研究者的猜测/盲法或治疗方式进行了分析。结果 纳入 40 项试验（3899 名受试者）。积极治疗组和假治疗组的平均致盲指数分别为 0.26（95% 置信区间：0.12, 0.41）和 0.01（-0.11, 0.14），这意味着积极治疗组中有 26% 的参与者认为他们接受了积极治疗，而只有 1%假的相信他们接受了假的治疗，超越偶然，即随机猜测。接受积极治疗的更大信念与双臂较大的臂内效应大小相关，而理想的盲法（即“随机猜测”和“一厢情愿”，表示两组都相信自己接受了积极治疗）显示的效应较小大小，对于臂间比较，效应大小和汇总致盲指数的相关性为 0.35 (p = 0.028)。我们观察到所有治疗方式均具有较大的假治疗效果，并且研究者（非）盲法的相关性较大，为 0.53（p = 0.046）。 结论 背痛试验中积极治疗的参与者更正确地猜测了治疗身份，而假治疗的参与者往往表现出成功的盲法。参与者和研究人员的过度正确猜测（可能反映较弱的盲法和/或明显的效应）表现出更大的效应量。在个体试验和荟萃分析中需要适当考虑盲法和假治疗对背痛的影响。