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Understanding the measurement properties of the incremental shuttle walk test in patients with severe asthma
Author(s) -
Majd Sally,
Hewitt Stacey M.,
Apps Lindsay D.,
Murphy Anna C.,
Bradding Peter,
Singh Sally J.,
Green Ruth H.,
Evans Rachael A.
Publication year - 2019
Publication title -
respirology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 85
eISSN - 1440-1843
pISSN - 1323-7799
DOI - 10.1111/resp.13519
Subject(s) - medicine , asthma , repeatability , physical therapy , treadmill , statistics , mathematics
Background and objective We investigated the repeatability and validity of the incremental shuttle walk test (ISWT) distance compared to peak oxygen uptake (VO 2pk ) during maximal incremental cycle ergometer (ICE) and treadmill (ITM) tests in adults with severe asthma. Methods Adults with severe asthma, Medical Research Council (MRC) dyspnoea ≥2, were recruited from specialists caring for patients with severe asthma. All participants performed three ISWT (familiarization and two subsequent tests on the same day), an ICE and an ITM in a randomized order, on separate days, to intolerance with expiratory gas analysis. Results A total of 50 patients (32 females, mean (SD), age: 54 (13) years, forced expiratory volume in 1 s (FEV 1 ): 1.9 (0.8) L and body mass index (BMI): 32 (6) kg/m 2 ) completed all five tests. The mean (SD) ISWT distance for each test was 400 (156), 418 (142) and 438 (157) m ( P = 0.001), respectively. There was a strong correlation between the ISWT distance with VO 2pk derived from ITM (r = 0.74, P < 0.001) and ICE (r = 0.75, P < 0.001). Conclusion There was a small increase in the mean ISWT distance on sequential testing. In clinical practice, the coefficient of repeatability and heteroscedasticity need to be considered when assessing whether a true change has occurred within an individual patient. The ISWT has validity compared to VO 2pk on both ICE and ITM, but they are not interchangeable.