Badia X, Monserrat S, Roset M, Herdman M
Catalan Institute of Public Health, University of Barcelona.
Qual Life Res. 1999 Jun;8(4):303-10. doi: 10.1023/a:1008952423122.
The feasibility, validity and reliability of the Time Trade-Off (TTO) and Visual Analogue Scale (VAS) methods in obtaining preference values for health states were compared in a random sample of the Spanish population (n = 294). Respondents valued 43 EuroQol-5D health states in face-to-face interviews. Convergent validity was assessed by examining the relationship between values, and the effect of sociodemographic and health variables on values was used as a means of assessing construct validity. Test-retest reliability was analysed in a subgroup of 50 respondents, using the intraclass correlation coefficient (ICC) and generalisability theory. Rates of non-response and missing data were low on both methods, though the VAS took considerably less time to administer. VAS and TTO values correlated highly (r = 0.92), though there were differences in the ordering of health states between methods, and in the number of health states rated worse than death. VAS values were compressed into a considerably smaller valuation space than TTO values. Respondents in higher educational categories assigned higher TTO values to 12 health states. Mean ICCs (95% CI) at individual level were 0.90 (0.88-0.92) and 0.84 (0.81-0.87) for the VAS and TTO, respectively. Generalisability analysis showed variance due to time to be 0 for both methods. In conclusion, the VAS was more feasible and slightly more reliable than the TTO, whilst doubt can be cast on the degree of convergent validity existing between the two methods. The compression of VAS values means that the TTO is likely to discriminate better between health states, and it may have greater construct validity if results from larger samples confirm that there are genuine differences between sociodemographic subgroups.
在西班牙人群的随机样本（n = 294）中，比较了时间权衡法（TTO）和视觉模拟评分法（VAS）获取健康状态偏好值的可行性、有效性和可靠性。受访者在面对面访谈中对43种欧洲五维度健康量表（EuroQol-5D）健康状态进行了赋值。通过检查赋值之间的关系来评估收敛效度，并将社会人口统计学和健康变量对赋值的影响作为评估结构效度的一种手段。在50名受访者的子样本中，使用组内相关系数（ICC）和概化理论分析了重测信度。两种方法的无应答率和缺失数据率都很低，不过VAS的施测时间要短得多。VAS和TTO值高度相关（r = 0.92），尽管两种方法在健康状态排序以及被评为比死亡更差的健康状态数量方面存在差异。VAS值被压缩到比TTO值小得多的估值空间。高等教育类别的受访者对12种健康状态赋予了更高的TTO值。VAS和TTO在个体水平上的平均ICC（95%CI）分别为0.90（0.88 - 0.92）和0.84（0.81 - 0.87）。概化分析表明，两种方法因时间导致的方差均为0。总之，VAS比TTO更可行且可靠性略高，而两种方法之间的收敛效度程度可能存在疑问。VAS值的压缩意味着TTO可能在区分健康状态方面表现更好，如果来自更大样本的结果证实社会人口统计学亚组之间存在真正差异，那么它可能具有更高的结构效度。
