Cham P M H, Chen S C, Grill J P, Jonk Y C, Warshaw E M
Department of Dermatology, University of Minnesota, Minneapolis, MN, U.S.A.
Br J Dermatol. 2007 May;156(5):922-8. doi: 10.1111/j.1365-2133.2006.07740.x.
Willingness-to-pay (WTP) is a health economics measure that has recently been used for skin diseases to evaluate patients' quality of life. However, the reliability of this measure has not been investigated in the dermatology literature and is essential in validating its use in health services research.
This study evaluated the test-retest reliability of self-reported annual income and WTP, a health economics measure of disease impact, in patients with toenail onychomycosis.
Forty-six patients enrolled in a randomized clinical trial comparing two different dosing regimens of terbinafine completed a self-administered questionnaire at baseline and 1 month later. The questionnaire asked: (i) how much patients would be willing to pay for a theoretical treatment with a cure rate of 85% for their current onychomycosis (10 categories: $0-50, $51-100, to > $800); and (ii) annual income (10 categories: $0-10,000 to > $200,000).
Forty-four patients reported WTP at both visits, and 55% reported the same WTP. The quadratic-weighted (Fleiss-Cohen) kappa statistic indicated moderate agreement (kappa = 0.50, 95% confidence interval, CI 0.24-0.75, P < 0.01) as did the Spearman rank-order correlation coefficient (r(s) = 0.57, P < 0.01; median difference = 0, P = 0.50). Strong agreement was shown among the 42 patients who reported income at both visits; 71% reported the same annual income category (kappa = 0.72, 95% CI 0.47-0.96, P < 0.01; r(s) = 0.68, P < 0.01; median difference = 0, P = 0.77). Age, disease severity and duration, previous therapy, self-reported annual income, and medication side-effects were not statistically associated with the reliability of WTP.
WTP and annual income demonstrated moderate and strong test-retest reliability, respectively. Self-reported WTP can serve as a reliable measure for future health economics research on onychomycosis.
支付意愿（WTP）是一种健康经济学指标，最近已被用于皮肤病领域以评估患者的生活质量。然而，该指标的可靠性在皮肤病学文献中尚未得到研究，而这对于验证其在卫生服务研究中的应用至关重要。
本研究评估了自我报告的年收入和支付意愿（一种疾病影响的健康经济学指标）在趾甲甲真菌病患者中的重测信度。
46名参与比较两种不同特比萘芬给药方案的随机临床试验的患者在基线时和1个月后完成了一份自我管理问卷。问卷询问：（i）患者愿意为其当前甲真菌病的一种治愈率为85%的理论治疗支付多少钱（10个类别：0 - 50美元、51 - 100美元，直至> 800美元）；以及（ii）年收入（10个类别：0 - 10,000美元至> 200,000美元）。
44名患者在两次访视时均报告了支付意愿，其中55%报告的支付意愿相同。二次加权（Fleiss - Cohen）kappa统计量表明一致性中等（kappa = 0.50，95%置信区间，CI 0.24 - 0.75；P < 0.01），Spearman等级相关系数（r(s) = 0.57，P < 0.01；中位数差异 = 0，P = 0.50）也显示出相同结果。在两次访视时均报告了收入的42名患者中显示出高度一致性；71%报告的年收入类别相同（kappa = 0.72，95% CI 0.47 - 0.96，P < 0.01；r(s) = 0.68，P < 0.01；中位数差异 = 0，P = 0.77）。年龄、疾病严重程度和病程、既往治疗、自我报告的年收入以及药物副作用与支付意愿可靠性之间无统计学关联。
支付意愿和年收入分别显示出中等和高度的重测信度。自我报告的支付意愿可为未来甲真菌病的健康经济学研究提供一种可靠的测量方法。
