Objective: To investigate the burden of ankylosing spondylitis (AS) in Spain, as baseline for economic evaluation of the use of biological agents.
Methods: A cross-sectional retrospective observational study was performed in 601 patients with AS in Spain, using a methodology developed in studies in the United Kingdom and Canada. Patients were mailed a questionnaire asking about their health-care consumption, out-of-pocket expenses, work capacity, need for informal care during the past 3 months, as well as quality of life. Patient's current functional status and disease activity level was assessed using the Bath functional and disease activity indexes (BASFI and BASDAI).
Results: The mean age (median) was 47.8 (12.4) years, and the mean disease duration was 18.8 years. Eighty percent of patients were male, and slightly more than half of patients below 65 years of age were working. The mean (median) BASDAI and BASFI scores were 4.3 (2.5) and 3.8 (2.9),respectively, and all levels of disease severity were represented. The mean (median) total annual cost per patient is estimated at euro 20,328 (euro 7920). Direct health care represented 22.8%, investments (adaptations of house and devices) and informal care 43.5%, and productivity losses 33.7%. Costs increased significantly with worsening disease, in particular diminishing physical function, covering a range between euro 5000 and euro 75,000 per patient and year. The mean (median) utility was 0.59 (0.30). Utility showed a significant inverse relation with BASFI and BASDAI, covering a range from 0.80 for patients with BASFI/BASDAI below 3 to 0.25 for patients with BASFI/BASDAI greater than 7.
Conclusions: As in studies in other countries, all types of costs accelerate steeply with worsening disease while utility decreases significantly, indicating the need to prevent disease progression.