The ASAS Health Index and Environmental Factors Item Set: validity and reliability of the Swedish translations in Swedish patients with ankylosing spondylitis

Abstract

Objectives To translate the Assessment of SpondyloArthritis international Society (ASAS) Health Index (HI) Environmental Factors Item Set (EFIS) into Swedish and culturally adapt it for a Swedish context, and to assess the construct validity of the Swedish version of the ASAS HI and test–retest reliability in ASAS HI and EFIS in Swedish patients with ankylosing spondylitis (AS). Method Translation and cross-cultural adaptation of the EFIS were carried out according to a forward–backward procedure consisting of five steps. The construct validity of the ASAS HI was tested using Spearman correlation with standard health outcomes for axial spondyloarthritis (axSpA). Reliability was analysed by internal consistency with the Cronbach’s alpha coefficient for ASAS HI, and test–retest reliability with intraclass correlation coefficients (ICCs) for ASAS HI and kappa agreement for the individual items of EFIS. Results The translation of EFIS showed acceptable face and content validity. ASAS HI showed an acceptable internal consistency (Cronbach’s alpha 0.79), and excellent test–retest reliability (ICC 0.87). Test–retest reliability for EFIS showed varied results, with kappa agreement for the individual items ranging from poor (−0.027) to good (0.80). Conclusions The Swedish version of ASAS HI proved to be valid and reliable and is recommended for assessing the impact of AS on global functioning and health. A Swedish version of EFIS has been produced and uploaded on the ASAS website. The EFIS proved to have acceptable face and content validity, and may contribute to the contextual interpretation of the ASAS HI.