Mapping the COPD Assessment Test onto EQ-5D.

Area of Science:

• Health Economics
• Clinical Outcomes Research
• Respiratory Medicine

Background:

• Health technology assessments (HTAs) for Chronic Obstructive Pulmonary Disease (COPD) rely on utility values for economic evaluations.
• The EuroQol five-dimensional questionnaire (EQ-5D) is a standard measure of health utility, but data may not always be available.
• The COPD Assessment Test (CAT) is a commonly used tool for assessing COPD severity.

Purpose of the Study:

• To develop and evaluate an algorithm for estimating EQ-5D-equivalent utilities from CAT scores.
• To assess the utility of such an algorithm in economic evaluations for COPD health technology assessments.

Main Methods:

• Utilized data from two multinational phase III clinical trials including EQ-5D-3L and CAT scores.
• Explored three methods for utility estimation: ordinary least-squares (OLS) regression, multinomial logistic regression, and a combined approach.
• Validated algorithms by comparing estimated utilities with actual EQ-5D-3L utilities, assessing treatment effects and disease severity impacts.

Main Results:

• An OLS regression algorithm demonstrated comparable performance to more complex models in estimating EQ-5D utilities.
• Systematic over- and underestimation of utilities were observed within specific EQ-5D-3L ranges (0.5-0.9).
• The OLS algorithm resulted in lower changes from baseline and narrower confidence intervals compared to actual EQ-5D-3L data.

Conclusions:

• The OLS algorithm can provide utility estimates for COPD treatment models when EQ-5D data is absent, but may underestimate treatment effects.
• Direct derivation of utilities from EQ-5D is recommended for UK health technology assessments of COPD treatments to ensure accuracy.
• Further research may be needed to refine algorithms for more precise utility estimation in specific patient populations or disease severities.