Evaluation of Ankylosing Spondylitis Quality of Life questionnaire: responsiveness of a new patient-reported outcome measure

Objective. To determine the responsiveness and minimal important change ( MIC) of Evaluation of Ankylosing Spondylitis Quality of Life (EASi-QoL), a reliable and valid patient-reported measure of AS-specific quality of life with four domains: physical function (PF), disease activity (DA), emotional well-being (EWB) and social participation (SP). Methods. A total of 1000 UK AS patients received a postal questionnaire including EASi-QoL. Comparative responsiveness of EASi-QoL was assessed against measures reflecting similar health domains in patients self-reporting an improvement in their AS-specific health at 6 months on a health transition question. Effect size (ES) statistics were calculated for all measures and MIC was determined for EASi-QoL. Comparative responsiveness was determined in a randomized trial of AS patients receiving etanercept (ETN) 50 mg weekly or SSZ 3 g daily. Results. Of 470 patients, 80 responding at 6 months reported health improvement. Responsiveness (ES) for EASi-QoL domains was superior or similar to comparator measures: DA 0.72 vs BASDAI 0.58; SP 0.52 vs SF-36 social functioning 0.29; PF 0.32 vs BASFI 0.28 and SF-36 PF 0.24; EWB 0.40 vs HADS-anxiety 0.13, HADS-depression 0.21 and SF-36 mental health 0.35. ES for the ASQoL was 0.40. Superior ES was seen in those improving somewhat. In the randomized trial, all EASi-QoL domains had superior responsiveness to comparator measures following ETN treatment. Following SSZ treatment, all EASi-QoL domains were highly responsive, but BASDAI and BASFI was more responsive than EASi-QoL(DA) and (PF), respectively. Conclusion. In patients reporting improvement during routine clinical practice or following treatment with ETN or SSZ, EASi-QoL domains have superior or comparable responsiveness than comparable measures.