Assessment of the relationship between measures of disease severity, quality of life, and willingness to pay in asthma

Objective: The primary objective was to evaluate the relationship between willingness-to-pay (WTP), quality-of-life (QOL), and disease-severity measures in patients with asthma. The hypothesis studied was that patients with asthma with more severe disease are willing to pay more for a hypothetical cure of asthma than those with less severe disease. Design setting/Patients and participants: One hundred patients with asthma were recruited from community pharmacies in Kentucky for 30-minute face-to-face interviews. Interventions: Spirometry assessed objective disease severity in terms of pulmonary function, while a multiple choice question measured subjective disease severity. The Medical Outcomes Study 36-item Short Form (SF-36) health survey and Asthma Technology of Patient Experience (Asthma TYPE) measured quality of life. WTP was obtained via a dichotomous choice contingent valuation question. Results: In this exploratory evaluation, WTP was significantly related to both objective disease severity (p = 0.02) and subjectively assessed disease severity (p = 0.01). For objective disease severity the mean monthly WTP was $US90 for mild asthma, $US131 for moderate asthma and $US331 for severe asthma and for subjective disease severity the mean monthly WTP was $US48 for mild asthma, $US166 for moderate asthma and $US241 for severe asthma. Conclusions: The results suggest that the WTP for a cure from asthma is related to both objective and subjective disease severity. These findings contribute to the case for construct validity of the dichotomous choice contingent valuation method in the healthcare sector.