FRI0568 MEASURING DAILY PHYSICAL ACTIVITY IN AXSPA PATIENTS: CONTENT VALIDITY AND MEASUREMENT PROPERTIES OF THE NEW AXSPA-SQUASH
Authors: M. Carbo, D. Paap, F. Maas, A. J. Baron, L. Van Overbeeke, M. Siderius, F. Wink, H. Bootsma, S. Arends, A. Spoorenberg
Journal: Annals of the Rheumatic Diseases (2020)

Background: The ASAS-EULAR recommendations for management of axial Spondyloarthritis (axSpA) includes that patients should be encouraged to exercise. 1 So far, there is no validated instrument for measuring daily physical activity in axSpA. Our previous study recommends to adapt the Short QUestionnaire to Assess Health-enhancing physical activity (SQUASH) to improve the validity in axSpA patients. 2 Objectives: AxSpA-disease specific adaptation of the physical activity questionnaire SQUASH to improve content validity and measurement properties. Methods: This study was conducted according to the OMERACT-filter within the Groningen Leeuwarden AxSpA (GLAS) cohort and was performed in two parts. Part 1: adaptation and evaluation of content validity using a qualitative stepwise approach with in-depth interviews with different healthcare professionals (n=9) and patients (n=8), field testing in patients (n=10), and consensus meeting for final adaptations. Thereafter, content validity (n=45) was tested by filling out axSpA-SQUASH and SQUASH in random order two weeks apart. Part 2: measurement properties were tested using the International Physical Activity Questionnaire (IPAQ) as comparator. Criterion validity (n=40): Spearman’s correlation with accelerometer as golden standard and classification accuracy of intensity. Construct validity (n=106): Spearman’s correlation with disease activity, physical functioning and quality of life as clinical outcome with expected fair to moderated associations. Test-retest reliability (n=45): intraclass correlation coefficients (ICC) after 2 weeks. Responsiveness (n=47): standardized response mean (SRM) after 3 months stratified by Ancor method. Results: In total 156 patients were included: mean age 48±13 years, 56% males, 72% HLA-B27 positive, symptom duration 21±13.3 years and ASDAS 2.0±1.0. Part 1: main adaptations were better explanation of intensities, adding answer option “not applicable”, examples were modernized, physiotherapy and activity “shopping” were added. Compared to the original SQUASH, the adapted axSpA-SQUASH measured a systematically higher activity count and had less missing values (8% vs. 32%). Part 2: criterion validity: axSpA-SQUASH correlated better with accelerometer compared to IPAQ (ρ=0.51 vs. ρ=0.35). Classification accuracy: accelerometer defined most activity as light (97%), whereas axSpA-SQUASH and IPAQ defined most activity as moderate intensity (55% and 62% resp.). Construct validity: correlations were low to moderate and strongest for axSpA-SQUASH compared to IPAQ. Construct validity: correlations were low to moderate and stronger for axSpA-SQUASH compared to IPAQ (BASDAI -0.27 vs -0.15, BASDAI –0.27 vs. -0.15, ASDAS -0.24 vs -0.09, BASFI -0.39vs. -0.21, ASQoL -0.39 vs. -0.35). Test-retest reliability: ICC axSpA-SQUASH: 0.80. Responsiveness: axSpA-SQUASH changed over time in the corresponding direction (Table 1). Feasibility: considered comprehensible and average completion time was 7 minutes. Table 1. Responsiveness of the axSpA-SQUASH versus change in BASDAI SRM 95% CI BASDAI T1 BASDAI T2 Improved (n=12) -0.36 -0.99 to 0.28 5.01 (2.10) 3.93 (1.60) Stable (n=21) 0.28 -0.18 to 0.73 3.76 (2.05) 3.76 (2.05) Decreased (n=14) 0.75 0.18 to 1.33 4.71 (1.96) 5.79 (2.42) Conclusion: The new axSpA-SQUASH resulted in improved content validity and measurement properties. It seems the most appropriate questionnaire and can be used to assess daily physical activity in patients with axSpA. References: [1] Van Der Heijde D et al. Ann Rheum Dis . 2017;76:978-91. [2] Arends S et al. Arthritis Res Ther . 2013;15:R99. Acknowledgments: We thank the ASAS for the reserch grant that supported this work. Disclosure of Interests: Marlies Carbo: None declared, Davy Paap: None declared, Fiona Maas: None declared, Anna Jetske Baron: None declared, Laura van Overbeeke: None declared, Mark Siderius: None declared, Freke Wink Consultant of: Abbvie, Janssen, Hendrika Bootsma Grant/research support from: Unrestricted grants from Bristol-Myers Squibb and Roche, Consultant of: Consultant for Bristol-Myers Squibb, Roche, Novartis, Medimmune, Union Chimique Belge, Speakers bureau: Speaker for Bristol-Myers Squibb and Novartis., Suzanne Arends Grant/research support from: Grant/research support from Pfizer, Anneke Spoorenberg: None declared