AIM: To map health-related quality of life (Qol) with clinical parameters BASFI and ASDAS-CRP measure, and other covariates. METHODS: Our prospective multicenter non-interventional observation study of ankylosing spondylitis (AS) collected data about QoL and clinical outcomes on the initial and four subsequent visits. We employed simple linear regression analysis of a cross-sectional dataset, and fixed effect, random effect and pooled linear regression of a longitudinal dataset. RESULTS: We showed that BASFI and ASDAS-CRP are very strong, robust predictors of EQ-5D utilities in all regression specifications together with sex (female), invalidity, and activity impairment. Additionally, the longitudinal regression analysis showed that a fixed effect model may be a viable alternative to the most commonly used random effect model or pooled linear regression due to the nature of our dataset. CONCLUSION: This is one of the first studies using a fixed effect model in longitudinal patient-level data, although, this method has been widely used in economics.

b Institute of Rheumatology Prague Czech Republic

c Clinic of Rheumatology 1st Faculty of Medicine Charles University Prague Prague Czech Republic

Department of Clinical Pharmacology Rheumatology University Hospital Plzen Plzen Czech Republic

e 3rd Internal Clinic University Hospital Olomouc Olomouc Czech Republic

Institute of Health Economics and Technology Assessment Prague Czech Republic

References provided by Crossref.org

Mapping Quality of Life (EQ-5D) from DAPsA, Clinical DAPsA and HAQ in Psoriatic Arthritis

EQ-5D studies in musculoskeletal and connective tissue diseases in eight Central and Eastern European countries: a systematic literature review and meta-analysis