Objective This study aimed to identify factors associated with EuroQoL–5 Dimensions, 5 Levels and Patient Acceptable Symptom State (PASS) and also to estimate health utility (HU) in Thai patients with ankylosing spondylitis (AS).

Methods This was a cross-sectional study of consecutive AS patients visiting Siriraj Hospital between May 31, 2012, and March 31, 2016. Demographic data and outcomes related to HU (Thai version of EuroQoL–5 Dimensions, 5 Levels), disease activity (Bath Ankylosing Spondylitis Disease Activity Index, Ankylosing Spondylitis Disease Activity Score–erythrocyte sedimentation rate or Ankylosing Spondylitis Disease Activity Score–C-reactive protein, number of tender and swollen joints, and enthesitis), and functional status (Bath Ankylosing Spondylitis Functional Index and Health Assessment Questionnaire) were collected. Regression analysis was used to explore factors associated with each EuroQOL–5 Dimensions (EQ-5D) domain, HU, and PASS.

Results Among 119 AS patients, the mean age was 40.4 years; 61.3% were male. The mean EQ-5D was 0.75. In univariate analysis, lower disease activity and less impaired function were significantly associated with higher HU and no to mild problem in each EQ-5D domain. In multivariate regression analysis, Bath Ankylosing SpondylitisDisease Activity Index, C-reactive protein, and Health Assessment Questionnaire adjusting for age explained 77.4% of the HU variance. Patients answering yes to PASS had significantly higher age, higher HU, and lower disease activity compared with those answering no to PASS. Usual activity and pain problems were the most important relations to PASS after adjusting for other domains and age.

Conclusions Disease activity and functional status in AS patients were significant factors related to HU and PASS. To improve quality of life, the goal of treatment should be achieving remission, improving function, and controlling pain.