<b><i>Background:</i></b> In patients with obstructive sleep apnea syndrome (OSAS), the preference-based, health-related quality of life in terms of utility has not been extensively studied. <b><i>Objective:</i></b> To address this point, we compared the performance of different instruments assessing utility in patients with OSAS undergoing continuous positive airway pressure (CPAP) therapy. <b><i>Materials and Methods:</i></b> Data of 208 patients with OSAS (28 women, mean ± SE age 54.4 ± 0.7 years, apnea-hypopnea index (AHI) 51.9 ± 1.8/h, Epworth sleepiness score 13.4 ± 0.2) participating in a randomized trial of different CPAP modalities over 2 years were analyzed. Evaluations included sleep studies, Epworth sleepiness scale, and several utility instruments that measure subjective health preference on a scale ranging from 1 (most preferred and perfect health) to 0 (least preferred and very poor health). <b><i>Results:</i></b> After 2 years of CPAP therapy, the mean ± SE AHI was 6.7 ± 1.5/h and Epworth score 7.9 ± 0.4, both <i>p</i> < 0.001 versus baseline. Baseline utilities and changes (95% confidence interval) after 2 years of CPAP therapy were EuroQol 5-dimensions 0.79 ± 0.01, 0.02 (0.00–0.05, <i>p</i> = 0.064); short-form 6-dimension medical outcome questionnaire 0.72 ± 0.01, 0.06 (0.04–0.08, <i>p</i> < 0.001); Euro-thermometer visual analog scale 0.70 ± 0.01, 0.09 (0.07–0.12, <i>p</i> < 0.001); time trade-off 0.82 ± 0.01, 0.03 (0.01–0.06, <i>p</i> = 0.002); and standard gamble 0.82 ± 0.01, −0.01 (−0.03 to 0.02, <i>p</i> = 0.712). <b><i>Conclusion:</i></b> The short-form 6-dimensions questionnaire, the Euro-thermometer, and the time trade-off instruments reflected the major clinical improvements in OSAS, while the EuroQoL 5-dimensions and standard gamble tests were not sensitive to CPAP effects. These results indicate that the evaluation of utility of a treatment for OSAS depends critically on the instrument used, which is important from an individual and societal perspective.
QALYs Without Bias? Non-Parametric Correction of Time Trade-Off and Standard Gamble Weights Based on Prospect Theory