Reliability of the 6-minute walking test smartphone application

Publication

Reliability of the 6-minute walking test smartphone application

Journal Paper/Review - Sep 13, 2019

Stienen Martin N., Regli Luca, Park Jon, Zygourakis Corinna C, Desai Atman, Veeravagu Anand, Ho Allen L, Sosnova Marketa, Maldaner Nicolai, Staartjes Victor E, Gautschi Oliver P, Ratliff John K

Citation

Stienen M, Regli L, Park J, Zygourakis C, Desai A, Veeravagu A, Ho A, Sosnova M, Maldaner N, Staartjes V, Gautschi O, Ratliff J. Reliability of the 6-minute walking test smartphone application. J Neurosurg Spine 2019:1-8.

Type

Journal Paper/Review (English)

Journal

J Neurosurg Spine 2019

Publication Date

Sep 13, 2019

Issn Electronic

1547-5646

Pages

1-8

Brief description/objective

OBJECTIVE
Objective functional measures such as the 6-minute walking test (6WT) are increasingly applied to evaluate patients with degenerative diseases of the lumbar spine before and after (surgical) treatment. However, the traditional 6WT is cumbersome to apply, as it requires specialized in-hospital infrastructure and personnel. The authors set out to compare 6-minute walking distance (6WD) measurements obtained with a newly developed smartphone application (app) and those obtained with the gold-standard distance wheel (DW).

METHODS
The authors developed a free iOS- and Android-based smartphone app that allows patients to measure the 6WD in their home environment using global positioning system (GPS) coordinates. In a laboratory setting, the authors obtained 6WD measurements over a range of smartphone models, testing environments, and walking patterns and speeds. The main outcome was the relative measurement error (rME; in percent of 6WD), with |rME| < 7.5% defined as reliable. The intraclass correlation coefficient (ICC) for agreement between app- and DW-based 6WD was calculated.

RESULTS
Measurements (n = 406) were reliable with all smartphone types in neighborhood, nature, and city environments (without high buildings), as well as with unspecified, straight, continuous, and stop-and-go walking patterns (ICC = 0.97, 95% CI 0.97-0.98, p < 0.001). Measurements were unreliable indoors, in city areas with high buildings, and for predominantly rectangular walking courses. Walking speed had an influence on the ME, with worse accuracy (2% higher rME) for every kilometer per hour slower walking pace (95% CI 1.4%-2.5%, p < 0.001). Mathematical adjustment of the app-based 6WD for velocity-dependent error mitigated the rME (p < 0.011), attenuated velocity dependence (p = 0.362), and had a positive effect on accuracy (ICC = 0.98, 95% CI 0.98-0.99, p < 0.001).

CONCLUSIONS
The new, free, spine-specific 6WT smartphone app measures the 6WD conveniently by using GPS coordinates, empowering patients to independently determine their functional status before and after (surgical) treatment. Measurements of 6WD obtained for the target population under the recommended circumstances are highly reliable.