Background Physical activity questionnaires are considered to be the most applicable method to assess daily physical activity in population studies because of participant convenience, minimal cost, and scoring flexibility. The International Physical Activity Questionnaire (IPAQ) and the Short QUestionnaire to Asses Health-enhancing physical activity (SQUASH) are recall questionnaires that have acceptable construct validity and moderate to high test-retest reliability in healthy populations.(1,2) Until now, the validity and reliability of these physical activity questionnaires have not been studied in patients with ankylosing spondylitis (AS).
Objectives To investigate the construct validity and test-retest reliability of the IPAQ and SQUASH in patients with AS.
Methods The self-report questionnaires IPAQ (long form) and SQUASH were compared with daily physical activity assessed using the ActiGraph accelerometer during 7 consecutive days (gold standard) in 63 AS outpatients. The IPAQ and SQUASH were administered on two different occasions approximately one week apart in 52 AS outpatients. All patients fulfilled the modified New York criteria for AS or the ASAS criteria for axial spondyloarthritis. Validity was examined by calculating Spearman’s and Pearson’s correlation coefficients between accelerometer activity counts and IPAQ and SQUASH total scores, respectively. Test-retest reliability of the IPAQ and SQUASH was investigated by calculating intraclass correlation coefficients (ICC) between the first and the second assessments of the questionnaires. Additionally, Bland-Altman analysis was performed.
Results Mean age of the in total 115 AS patients was 45 years (SD ± 12), median disease duration was 16 years (range 0-54), and 62% were male. IPAQ and SQUASH total scores correlated significantly with accelerometer outcome: ρ=0.38 and r=0.35, respectively. ICC’s between first and second assessments of the IPAQ and SQUASH were 0.83 and 0.89, respectively. Bland-Altman analyses showed no systemic bias, but in particular for the IPAQ the 95% limits of agreement were wide.
Conclusions Both physical activity questionnaires showed moderate construct validity. The SQUASH showed good test-retest reliability, superior to the IPAQ. These results indicate that the SQUASH can be used to assess daily physical activity in AS population studies.
Craig CL, Marshall AL, Sjostrom M, et al. International physical activity questionnaire: 12-country reliability and validity. Med Sci Sports Exerc. 2003;35:1381-95.
Wendel-Vos GC, Schuit AJ, Saris WH, et al. Reproducibility and relative validity of the short questionnaire to assess health-enhancing physical activity. J Clin Epidemiol. 2003;56:1163-9.
Disclosure of Interest None Declared