Department of Pharmaceutical Economics and Policy, School of Pharmacy, University of Southern California, Los Angeles, CA, USA.
Med Decis Making. 2010 Jan-Feb;30(1):58-67. doi: 10.1177/0272989X07312478. Epub 2008 Jun 12.
A common assertion is that rating scale (RS) values are lower than both standard gamble (SG) and time tradeoff (TTO) values. However, differences among these methods may be due to method specific bias. Although SG and TTOs suffer systematic bias, RS responses are known to depend on the range and frequency of other health states being evaluated. Over many diverse studies this effect is predicted to diminish. Thus, a systematic review and data synthesis of RS-TTO and RS-SG difference scores may better reveal persistent dissimilarities.
The purpose of this study was to establish through systematic review and meta-analysis the net effect of biases that endure over many studies of utilities.
A total of 2206 RS and TTO and 1318 RS and SG respondents in 27 studies of utilities participated. MEDLINE was searched for data from 1976 to 2004, complemented by a hand search of full-length articles and conference abstracts for 9 journals known to publish utility studies, as well as review of results and additional recommendations by 5 outside experts in the field. Two investigators abstracted the articles. We contacted the investigators of the original if required information was not available.
No significant effect for RS and TTO difference scores was observed: effect size (95% confidence interval [CI]) = 0.04 (-0.02, 0.09). In contrast, RS scores were significantly lower than SG scores: effect size (95% CI ) =-0.23 (-0.28, -0.19). Correcting SG scores for 3 known biases (loss aversion, framing, and probability weighting) eliminated differences between RS and SG scores: effect size (95% CI ) = 0.01 (-0.03, 0.05). Systematic bias in the RS method may exist but be heretofore unknown. Bias correction formulas were applied to mean not individual utilities.
The results of this study do not support the common view that RS values are lower than TTO values, may suggest that TTO biases largely cancel, and support the validity of formulas for correcting SG bias.
普遍的观点认为，等级量表（RS）的值低于标准博弈（SG）和时间权衡（TTO）的值。然而，这些方法之间的差异可能是由于方法特定的偏差。尽管 SG 和 TTO 存在系统偏差，但 RS 反应已知取决于正在评估的其他健康状态的范围和频率。在许多不同的研究中，这种效应预计会减弱。因此，对 RS-TTO 和 RS-SG 差值进行系统审查和数据综合可以更好地揭示持久的差异。
本研究的目的是通过系统审查和荟萃分析，确定在许多效用研究中持续存在的偏差的净效应。
共有 27 项效用研究中的 2206 名 RS 和 TTO 以及 1318 名 RS 和 SG 受访者参与。从 1976 年至 2004 年在 MEDLINE 上搜索数据，并通过对 9 种已知发表效用研究的期刊的全文文章和会议摘要进行手工搜索，以及由该领域的 5 位外部专家对结果进行审查和提出额外建议来补充数据。两名调查员摘录了文章。如果无法获得所需信息，我们会联系原始调查员。
RS 和 TTO 差值的得分没有显著影响：效应大小（95%置信区间 [CI]）= 0.04（-0.02，0.09）。相比之下，RS 得分明显低于 SG 得分：效应大小（95%CI）=-0.23（-0.28，-0.19）。通过校正 3 种已知偏差（损失厌恶、框架和概率加权），消除了 RS 和 SG 得分之间的差异：效应大小（95%CI）=0.01（-0.03，0.05）。RS 方法可能存在系统偏差，但迄今为止未知。偏差校正公式应用于平均值而不是个体效用。
本研究的结果不支持 RS 值低于 TTO 值的常见观点，可能表明 TTO 偏差在很大程度上相互抵消，并支持校正 SG 偏差的公式的有效性。
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