Objective: To assess the discriminative properties of the EuroQol five-dimension questionnaire (EQ-5D) with respect to COPD severity according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria in a large multinational study.
Methods: Baseline EQ-5D visual analog scale (VAS) scores, EQ-5D utility scores, and St. George Respiratory Questionnaire scores were obtained from a subset of patients in the Understanding the Potential Long-term Impact on Function with Tiotropium trial, which was a 4-year placebo-controlled trial designed to assess the effect of tiotropium on the rate of decline in FEV1 in COPD patients aged ≥ 40 years, an FEV1 of < 70% predicted, an FEV1/FVC ratio of ≤ 70%, and a smoking history of ≥ 10 pack-years.
Results: A total of 1,235 patients (mean post bronchodilator FEV1, 48.8% predicted) from 13 countries completed the EQ-5D. The EQ-5D VAS and utility scores differed significantly among patients in GOLD stages 2, 3, and 4, also after correction for age, sex, smoking, body mass index (BMI), and comorbidity (p < 0.001). The mean EQ-5D VAS scores for patients in GOLD stages 2, 3, and 4 were 68 (SD, 16), 62 (SD, 17), and 58 (SD, 16), respectively. The mean utility scores were 0.79 (SD, 0.20) for patients in GOLD stage 2, 0.75 (SD, 0.21) for patients in GOLD stage 3, and 0.65 (SD, 0.23) for patients in GOLD stage 4. Effect sizes for the difference in utility scores between patients in GOLD stages 3 and 4 were more than twice as high as those for the difference between patients in GOLD stages 2 and 3. Gender, postbronchodilator FEV1 percent predicted, the number of hospital admissions and emergency department visits in the year prior to baseline measurements, measures of comorbidity, and BMI were independently associated with EQ-5D utility. EQ-5D utility scores also differed between patients from different countries. French patients especially had lower utility scores than US patients. Utility scores calculated with the US value set were on average 5% higher than those calculated with the UK value set.
Conclusions: Increasing severity of COPD was associated with a significant decline in EQ-5D VAS scores and utility scores. These results demonstrate that a generic instrument can assess COPD impact on quality of life and that the scores discriminate between patient groups of known severity. These utility scores will be useful in cost-effectiveness assessments.