Comparing the construct validity of measurement instruments for pain and stiffness in patients with axial spondyloartwhritis: cross-sectional analysis in the OASIS cohort
RMD Open, vol. 10, pp. e004775
Abstract
OBJECTIVES: To compare the construct validity, including discrimination between known groups, of three pain and three morning stiffness (MS) measurement instruments. METHODS: Patients with radiographic axial spondyloarthritis with 8-year data from the Outcome in Ankylosing Spondylitis International Study cohort were assessed cross-sectionally. Three instruments for pain and three for MS, all self-reported and scored 0-10, were compared. Construct validity was evaluated by testing (1) hypothesis of correlations' strength and (2) discrimination between known groups using standardised mean differences (SMD) across external constructs. Influence of contextual factors (CFs) on SMDs was investigated. RESULTS: Of 85 patients, mean age was 54 (SD 11), mean symptom duration 31 (11) years, 71% males. All six instruments showed a good construct validity by fulfilling >75% of the hypotheses for the strength of correlation. Neck/back/hip pain (Bath Ankylosing Spondylitis Disease Activity Index-Question 2, BASDAI-Q2) and total back pain had higher SMDs compared with back pain at night across all between-group comparisons, with BASDAI-Q2 performing mostly slightly better (eg, SMD for external construct Axial Spondyloarthritis Disease Activity Score (ASDAS; ≥2.1 vs <2.1): 1.87 (BASDAI-Q2) vs 1.56 (total back pain) vs 1.07 (back pain at night)). MS-severity and severity/duration had higher SMDs across all external constructs (with MS-severity slightly better), while MS-duration performed worse (eg, SMD external construct ASDAS: 1.51 (MS-severity) and 1.39 (MS-severity/duration) vs 1.16 (MS-duration)). Influence of CFs on known group discrimination was limited. CONCLUSIONS: The recommended Assessment of SpondyloArthritis international Society Core Outcome Set (ASAS-COS) pain measurement instrument total back pain BASDAI-Q2 has the best known group discrimination. For MS, the ASAS-COS stiffness measure (MS-severity/duration) performs well although MS-severity even slightly better. Known group discrimination is overall stable across CFs.
Authors 8
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Tel Aviv Sourasky Medical Center · Maastricht University · Care and Public Health Research Institute
Affiliation as printed
Care and Public Health Research Institute (CAPHRI), Maastricht University, Maastricht, Netherlands
Rheumatology, Tel Aviv Sourasky Medical Center–Ichilov, Tel Aviv, Israel
Rheumatology, Tel Aviv Sourasky Medical Center-Ichilov, Tel Aviv, Israel
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King's College Hospital Charity · King's College Hospital
Affiliation as printed
Centre for Rheumatic Diseases, King’s College Hospital Charity, London, UK
Rheumatology, King’s College Hospital Charity, London, UK
Centre for Rheumatic Diseases, King's College Hospital Charity, London, UK
Rheumatology, King's College Hospital Charity, London, UK
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Maastricht University Medical Centre · Maastricht University · Care and Public Health Research Institute
Affiliation as printed
Care and Public Health Research Institute (CAPHRI), Maastricht University, Maastricht, Netherlands
Department of Rheumatology, Maastricht University Medical Centre+, Maastricht, Netherlands
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Odense University Hospital · Bispebjerg Hospital
Affiliation as printed
Clinical Research, Odense University Hospital, Odense, Denmark
Section for Biostatistics and Evidence-Based Research, Bispebjerg Hospital, Kobenhavn, Denmark
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Leiden University Medical Center
Affiliation as printed
Rheumatology, Leiden University Medical Center, Leiden, Netherlands
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Zuyderland Medisch Centrum · Amsterdam University Medical Centers
Affiliation as printed
Clinical Immunology and Rheumatology, Amsterdam University Medical Centres, Amsterdam, Netherlands
Rheumatology, Zuyderland Medical Centre, Sittard-Geleen, Netherlands
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Maastricht University Medical Centre · Maastricht University · Care and Public Health Research Institute
Affiliation as printed
Care and Public Health Research Institute (CAPHRI), Maastricht University, Maastricht, Netherlands
Department of Rheumatology, Maastricht University Medical Centre+, Maastricht, Netherlands
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Leiden University Medical Center · Zuyderland Medisch Centrum
Affiliation as printed
Department of Rheumatology, Zuyderland Medical Centre Heerlen, Heerlen, Netherlands
Rheumatology, Leiden University Medical Center, Leiden, Netherlands
Rheumatology, Leiden University Medical Center, Leiden, Netherlands sofiaramiro@gmail.com
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