Background The ASAS Health Index (ASAS HI) was developed to measure functioning and health in patients with spondyloarthritis (SpA) aiming to better define the impact of disease in these patients. The 17 questions of the questionnaire (range 0–17, with a lower score indicating a better health status) have now been translated into 18 languages worldwide. Face validity and feasibility (time of completion) have already been assessed in a field test.1
Objectives To test construct validity, discrimination across relevant health states, reliability and responsiveness of the original English version and the 16 translations of the ASAS HI in 23 countries
Methods A convenient sample of SpA patients fullfilling the ASAS classification criteria for either axial (axSpA) or peripheral SpA (pSpA) were included into the study from 33 centers of 23 countries worldwide. Data were collected by the local rheumatologist. Construct validity against other health outcomes was evaluated by Spearman correlation. Discrimination across patient reported health states was decribed. Test-retest reliability was assessed by intraclass correlation coefficient (ICC) in patients without treatment changes (stable disease state, interval 4–7 days). In those patients who required a therapeutic change because of high disease activity, responsiveness was tested (standardized response mean (SRM)) after 2–24 weeks depending on the type of medication.
Results 1548 patients were included: 64.9% male, mean (SD) age 42.0 (13.4) years, mean (SD) BASDAI 4.1 (2.5)). There were 1299 patients with axSpA (375 nr-axSpA and 924 AS patients) and 256 patients with pSpA. The total score of the ASAS HI was 6.7 ± 4.3 (mean ± SD). Floor or ceiling effects were limited (0.8 and 6.9%, respectively). Convergent validity ranged as hypthesized with Spearman correlations from low (age: 0.10) to good (BASDAI: 0.70). ASAS HI scores showed a high internal consistency with a Cronbachs-α of 0.93. The ASAS HI discriminated well between patients with different stages of disease activity and function irrespective of the tool applied (ASDAS, BASDAI and BASFI) (table). The groups with greater disease activity and more impaired functioning had higher mean ASAS HI scores (indicating impaired functioning) than those with lower disease activity. Reliability (tested in 578 patients) was good (ICC: 0.87 (95%CI 0.84 to 0.89), p<0.01) and comparable across all disease subtypes. Sensitivity to change (tested in 246 patients) showed a moderate SRM of -0.44 for NSAIDs (n=75 patients), 0.69 for DMARDs (n=41) and -0.85 for TNFi (n=127). The smallest detectable change in this cohort was 3.0.
Conclusions The ASAS HI is a valid, reliable and responsive measure of disease severity in people affetcte by SpA. It should be used in clinical trials to evaluate the impact of SpA and its treatment on overall functioning and health.
Ann Rheum Dis 2014; 73 (suppl II): 463
Disclosure of Interest None declared