Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors
Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors
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DOI：
10.1503/cmaj.120744
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发表时间：
2013-03-05
影响因子：
14.6
通讯作者：
Brorson, Stig
中科院分区：
文献类型：
--
作者：
Hrobjartsson, Asbjorn;Thomsen, Ann Sofia Skou;Brorson, Stig
背景：临床试验通常在没有盲目结果评估者的情况下进行，尽管存在偏见的风险。我们希望评估非盲法结果评估对包含主观测量量表结果的随机临床试验的估计效果的影响。方法：我们对随机临床试验进行系统综述，对相同测量量表结果进行盲法和非盲法评估。我们检索了PubMed、EMBASE、QicINFO、CINAHL、Cochrane Central Register of Control Trials、Highwire Press和Google Scholar，以获取相关研究。两名调查人员就纳入试验和结果规模达成一致。对于每个试验，我们计算了效应大小的差异(即，非盲化评估和盲化评估之间的标准化平均差异)。效应大小的差异小于0表明非盲法评估者对效应产生了更乐观的估计。我们使用逆方差随机效应Meta分析合并效应大小的差异，并使用Meta回归来确定差异的潜在原因。结果：我们的综述纳入了24项试验。主要的荟萃分析包括有主观结果的16项试验(涉及2854名患者)。如果基于非盲法评估者(效应大小的合并差异-0.23[95%可信区间(CI)-0.40至-0.06])，则估计的治疗效果更有利。相对而言，非盲法评估者将合并效应大小夸大了68%(95%可信区间为14%，比230%为高)。异质性是中等的(P=46%，P=0.02)，不能用元回归来解释。解释：我们为主观测量量表结果的随机临床试验中的观察者偏差提供了经验证据。如果不能使评估者对这类试验的结果视而不见，就会产生重大偏见的高风险。
Background: Clinical trials are commonly done without blinded outcome assessors despite the risk of bias. We wanted to evaluate the effect of nonblinded outcome assessment on estimated effects in randomized clinical trials with outcomes that involved subjective measurement scales.Methods: We conducted a systematic review of randomized clinical trials with both blinded and nonblinded assessment of the same measurement scale outcome. We searched PubMed, EMBASE, PsycINFO, CINAHL, Cochrane Central Register of Controlled Trials, HighWire Press and Google Scholar for relevant studies. Two investigators agreed on the inclusion of trials and the outcome scale. For each trial, we calculated the difference in effect size (i.e., standardized mean difference between nonblinded and blinded assessments). A difference in effect size of less than 0 suggested that nonblinded assessors generated more optimistic estimates of effect. We pooled the differences in effect size using inverse variance random-effects meta-analysis and used metaregression to identify potential reasons for variation.Results: We included 24 trials in our review. The main meta-analysis included 16 trials (involving 2854 patients) with subjective outcomes. The estimated treatment effect was more beneficial when based on nonblinded assessors (pooled difference in effect size -0.23 [95% confidence interval (CI) -0.40 to -0.06]). In relative terms, nonblinded assessors exaggerated the pooled effect size by 68% (95% CI 14% to 230%). Heterogeneity was moderate (P = 46%, p = 0.02) and unexplained by metaregression.Interpretation: We provide empirical evidence for observer bias in randomized clinical trials with subjective measurement scale outcomes. A failure to blind assessors of outcomes in such trials results in a high risk of substantial bias.