JMIR Publications

ABSTRACT

Background:

Walking disturbances are a common dysfunction in persons with multiple sclerosis (MS). The 2-minute walking test (2MWT) is widely used to quantify walking speed. We implemented a smartphone 2MWT (s2MWT) in MS sherpa, an app for persons with MS. When performing the s2MWT users of the app are instructed to walk as fast as safely possible for two minutes in the open air, while the app records their movement and calculates the distance walked.

Objective:

The aim of this study was to investigate the concurrent validity and test-retest reliability of the MS sherpa s2MWT.

Methods:

We performed a validation study in 25 persons with relapsing-remitting MS and 79 healthy control (HC) subjects. In the HC group, 21 subjects were matched to the persons with MS with regard to age, gender, and education and these followed the same assessment schedule as the persons with MS (the “HC matched” group) whereas 58 subjects had a less intense assessment schedule to determine reference values (the “HC normative” group). Intraclass correlation coefficients (ICCs) were determined between the distance measured by the s2MWT and the distance measured using distance markers on the pavement during these s2MWT assessments. ICCs were also determined for test-retest reliability, which were derived from 10 smartphone tests per study participant, with 3 days in between each test. Seven study participants with MS were interviewed regarding their experiences with the s2MWT.

Results:

In total, 755 s2MWTs were done. The adherence rate for the persons with MS and HC matched group was 92%. The calculated distance walked on the s2MWT was, on average, 4.56% higher than the distance measured using distance markers, with a standard deviation of 10.7%. An ICC of 0.817 was found for the concurrent validity of the s2MWT in the combined analysis of persons with MS and HC subjects. Average ICCs of nine test-retest reliability analyses of the s2MWT for persons with MS and the HC matched group were 0.649 and 0.600, respectively, while the average ICC of two test-retest reliability analyses of the s2MWT for the HC normative group was 0.700. The interviewed study participants found the s2MWT easy to perform, but they also expressed that the test results can be confronting and that a pressure to reach a certain distance can be experienced.

Conclusions:

The high correlation between s2MWT distance and the conventional 2MWT distance indicates a good concurrent validity. Similarly, high correlations underpin a good test-retest reliability of the s2MWT. We conclude that the s2MWT can be used to measure the distance persons with MS walk in 2 minutes outdoors near their home, from which both clinical studies and clinical practice can benefit.