Content validity of the ASQoL for use in a non-radiographic axial spondyloarthritis population: a qualitative study

PURPOSE: The ankylosing spondylitis quality of life (ASQoL) instrument is widely used to assess health-related quality of life in patients with ankylosing spondylitis (AS). We assessed the relevance of the ASQoL items in patients with non-radiographic axial spondyloarthritis (nr-axSpA), a distinct subgroup within the axSpA disease spectrum. METHODS: This observational, cross-sectional, qualitative interview study recruited patients from clinic settings. Interviews from patients with axSpA who participated in a prior qualitative study were also used. Patients initially underwent a concept elicitation interview using open-ended questions to evaluate relevance of the concepts measured by the ASQoL. They then completed the ASQoL and underwent a cognitive interview to assess their understanding of the items, instructions and response options. Transcripts from patients who participated in the previous qualitative study (who did not complete the ASQoL or undergo cognitive interview) were evaluated to identify expressions of the concepts in the ASQoL. RESULTS: A total of 18 patients with nr-axSpA participated. The concept elicitation interview findings supported the relevance of the ASQoL items. Cognitive interviews determined that the ASQoL was easily understood; the 13 new patients chose a response for each item that matched their experience with nr-axSpA. Transcripts for the five previously interviewed patients confirmed the concepts presented in the ASQoL items were relevant and important to their experience of living with nr-axSpA. CONCLUSIONS: Our results represent an important first step in confirming the relevance of the concepts in the ASQoL to patients with nr-axSpA, supporting quantitative assessment of ASQoL validity in this population. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s11136-020-02552-z) contains supplementary material, which is available to authorized users.