RT Journal Article SR Electronic T1 Measuring quality of life of patients with axial spondyloarthritis for economic evaluation JF RMD Open JO RMD Open FD EULAR SP e001955 DO 10.1136/rmdopen-2021-001955 VO 8 IS 1 A1 Monica Hernandez Alava A1 Allan Wailoo A1 Georgios Chrysanthou A1 Filipe Barcelos A1 Floris A van Gaalen A1 Helena Santos A1 Karen Minde Fagerli A1 Laura Gago A1 Maria Margarida Cunha A1 Marleen van de Sande A1 Maura C Couto A1 Miguel Bernardes A1 Roberta Ramonda A1 Sofia Exarchou A1 Pedro D Carvalho A1 Desirée van der Heijde A1 Pedro M Machado YR 2022 UL http://rmdopen.bmj.com/content/8/1/e001955.abstract AB Objectives To estimate the relationship between EQ5D (three levels, UK version) and the Ankylosing Spondylitis Disease Activity Score (ASDAS) for use in the economic evaluation of health technologies for people with axial spondyloarthritis (axSpA). To compare against the relationship with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI).Methods An electronic, prospective, Portuguese, nationwide, rheumatic disease register (Reuma.pt) provided data on 1140 patients (5483 observations) with a confirmed diagnosis of axSpA. We estimated models of EQ5D as a function of ASDAS, alone or in combination with measures of functional impairment, using bespoke mixture models which reflect the complex distributional features of EQ5D. The SPondyloArthritis Caught Early cohort provided data from 344 patients (1405 observations) in four European countries and was used for validation. A previously published model of BASDAI/Bath Ankylosing Spondylitis Functional Index (BASFI) was also used to generate predicted EQ5D scores and model performance compared.Results A non-linear relationship exists between EQ5D from ASDAS. The final model included ASDAS, ASDAS squared, age and age squared and demonstrated close fit in both datasets except where data were sparse for patients with very high levels of disease activity (ASDAS >4). This finding held in the validation dataset. Models that included BASFI improved model fit. The ASDAS based models fit the data marginally less well than models using BASDAI.Conclusions Mapping models linking ASDAS to EQ5D allow results from clinical studies to be used in economic evaluation of health technologies with confidence. There is some loss of information compared with BASDAI but this has only a marginal impact.Data may be obtained from a third party and are not publicly available. Data from the SPACE and reuma.pt registries can be obtained by contacting the investigators of those studies.