Instrument selection for the ASAS core outcome set for axial spondyloarthritis.

OBJECTIVES: To define the instruments for the Assessment of SpondyloArthritis international Society-Outcomes Measures in Rheumatology (ASAS-OMERACT) core domain set for axial spondyloarthritis (axSpA). METHODS: An international working group representing key stakeholders selected the core outcome instruments following a predefined process: (1) identifying candidate instruments using a systematic literature review; (2) reducing the list of candidate instruments by the working group, (3) assessing the instruments' psychometric properties following OMERACT filter 2.2, (4) selection of the core instruments by the working group and (5) voting and endorsement by ASAS. RESULTS: The updated core set for axSpA includes seven instruments for the domains that are mandatory for all trials: Ankylosing Spondylitis Disease Activity Score and Numerical Rate Scale (NRS) patient global assessment of disease activity, NRS total back pain, average NRS of duration and severity of morning stiffness, NRS fatigue, Bath Ankylosing Spondylitis Function Index and ASAS Health Index. There are 9 additional instruments considered mandatory for disease-modifying antirheumatic drugs (DMARDs) trials: MRI activity Spondyloarthritis Research Consortium of Canada (SPARCC) sacroiliac joints and SPARCC spine, uveitis, inflammatory bowel disease and psoriasis assessed as recommended by ASAS, 44 swollen joint count, Maastricht Ankylosing Spondylitis Enthesitis Score, dactylitis count and modified Stoke Ankylosing Spondylitis Spinal Score. The imaging outcomes are considered mandatory to be included in at least one trial for a drug tested for properties of DMARD. Furthermore, 11 additional instruments were also endorsed by ASAS, which can be used in axSpA trials on top of the core instruments. CONCLUSIONS: The selection of the instruments for the ASAS-OMERACT core domain set completes the update of the core outcome set for axSpA, which should be used in all trials.

An Assessment in SpondyloArthritis International Society (ASAS)-endorsed definition of clinically important worsening in axial spondyloarthritis based on ASDAS.

INTRODUCTION: In a previous phase, 12 draft definitions for clinically important worsening in axial spondyloarthritis (axSpA) were selected, of which 3 were based on absolute changes in Ankylosing Spondylitis Disease Activity Score (ASDAS)-CRP (ASDAS). The objective here was to select the best cut-off for ASDAS for clinically important worsening in axSpA for use in clinical trials and observational studies. METHODS: An international longitudinal prospective study evaluating stable patients with axSpA was conducted. Data necessary to calculate ASDAS were collected at two consecutive visits (spaced 7 days to 6 months). Sensitivity and specificity of the three cut-offs for change in ASDAS were tested against the patient's subjective assessment of worsening as the external standard (ie, the patient reporting that he had worsened and felt a need for treatment intensification). Final selection was made by a consensus and voting procedure among Assessment of SpondyloArthritis International Society (ASAS) members. RESULTS: In total, 1169 patients with axSpA were analysed: 64.8% were male and had a mean age of 41.7 (SD 12.4) years. At the second visit, 127 (10.9%) patients judged their situation as worsened.Sensitivity and specificity for an increase of at least 0.6, 0.9 and 1.1 ASDAS points to detect patient-reported worsening were 0.55 (Se) and 0.91 (Sp), 0.38 (Se) and 0.96 (Sp), and 0.33 (Se) and 0.98 (Sp), respectively. The ASAS consensus was to define clinically important worsening as an increase in ASDAS of at least 0.9 points. CONCLUSION: This data-driven ASAS consensus process resulted in an ASDAS-based cut-off value defining clinically important worsening in axSpA for use in trials.

Measurement properties of the ASAS Health Index: results of a global study in patients with axial and peripheral spondyloarthritis.

OBJECTIVES: To evaluate construct validity, interpretability, reliability and responsiveness as well as determination of cut-off points for good and poor health within the original English version and the 18 translations of the disease-specific Assessment of Spondyloarthritis international Society Health Index (ASAS HI) in 23 countries worldwide in patients with spondyloarthritis (SpA). METHODS: A representative sample of patients with SpA fulfilling the ASAS classification criteria for axial (axSpA) or peripheral SpA was used. The construct validity of the ASAS HI was tested using Spearman correlation with several standard health outcomes for axSpA. Test-retest reliability was assessed by intraclass correlation coefficients (ICCs) in patients with stable disease (interval 4-7 days). In patients who required an escalation of therapy because of high disease activity, responsiveness was tested after 2-24weeks using standardised response mean (SRM). RESULTS: Among the 1548 patients, 64.9% were men, with a mean (SD) age 42.0 (13.4) years. Construct validity ranged from low (age: 0.10) to high (Bath AnkylosingSpondylitisFunctioning Index: 0.71). Internal consistency was high (Cronbach's α of 0.93). The reliability among 578 patients was good (ICC=0.87 (95% CI 0.84 to 0.89)). Responsiveness among 246 patients was moderate-large (SRM=-0.44 for non-steroidal anti-inflammatory drugs, -0.69 for conventional synthetic disease-modifying antirheumatic drug and -0.85 for tumour necrosis factor inhibitor). The smallest detectable change was 3.0. Values ≤5.0 have balanced specificity to distinguish good health as opposed to moderate health, and values ≥12.0 are specific to represent poor health as opposed to moderate health. CONCLUSIONS: The ASAS HI proved to be valid, reliable and responsive. It can be used to evaluate the impact of SpA and its treatment on functioning and health. Furthermore, comparison of disease impact between populations is possible.