Quality of life and time trade-off utility measures in patients with coronary artery disease.
BACKGROUND
Contemporary clinical trials commonly measure quality of life and medical costs to establish whether therapies are both effective and cost effective. Cost-effectiveness analysis, however, requires a measure of patient utility or preferences for various health states. Because utilities are not often measured directly, we sought to develop a method of translating standard quality-of-life scales into a patient utility measure.


METHODS
Five hundred fifty-three patients enrolled in the Bypass Angioplasty Revascularization Investigation Study of Economics and Quality of Life completed a battery of quality-of-life measures and a time trade-off utility assessment an average of 7.3 years after random assignment.


RESULTS
The mean time trade-off score was 8.54 (SD = 2.53) out of a maximum of 10; median score was 9.95. The distribution of scores was skewed, with 12% of patients at the highest possible score of 10. Patients with recurrent angina had significantly lower time trade-off scores than patients without angina (mean 7.03 vs 8.70, P <.05). Time trade-off scores were moderately correlated with each quality-of-life measure (Spearman coefficients 0.38-0.52). Time trade-off scores could be predicted by combinations of 4 (r2 = 0.29), 5 (r2 = 0.31), or 6 (r2 = 0.32) variables.


CONCLUSIONS
Time trade-off utility scores can be inferred from commonly used quality-of-life measures. Angina significantly reduces patient utility scores.
Melsop
Kathryn A
KA
Department of Health Research and Policy, Stanford University School of Medicine, Stanford, Calif 95305-5405, USA.
Boothroyd
Derek B
DB
Hlatky
Mark A
MA
D017677:Age Distribution; D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D001026:Coronary Artery Bypass; D003327:Coronary Disease / Q000523:psychology* / Q000628:therapy; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D017678:Sex Distribution; D013997:Time Factors