Abstract
Objective
To determine the validity of the 6-minute walk test (6MWT) as an outcome measure to
evaluate walking capacity in ambulatory patients with amyotrophic lateral sclerosis
(ALS).
Design
Observational study.
Setting
Multidisciplinary ALS clinic at an academic medical center.
Participants
Patients with ALS (N=186) who ambulate without (stage I) or with (stage II) an assistive
device.
Interventions
Not applicable.
Main Outcome Measure
Walking distance obtained from the 6MWT.
Results
Participants performed the 6MWT, 25-foot walk test (25FWT), Timed Up and Go (TUG)
test, lower extremity maximum voluntary isometric contraction (MVIC), ALS Functional
Rating Scale-Revised (ALSFRS-R), and forced vital capacity (FVC). Walking capacity
was reduced to 66% predicted of healthy subjects (75.2%±22% in stage I; 42.6%±22%
in stage II). The 6MWT correlated with all other outcome measures in ambulatory patients
with ALS (25FWT: r=−.74, P≤.0001; TUG test: r=−.80, P≤.0001; MVIC: r=.64, P≤.0001; percent predicted FVC: r=.25, P≤.0007; ALSFRS-R: r=.52, P≤.0001; ALSFRS-R gross motor subscore: r=.71, P≤.0001). When ambulatory patients with ALS were stratified by stage of ambulation,
the 6MWT was associated with all other outcome measures in stage I (25FWT: r=−.56, P≤.0001; TUG test: r=−.66, P≤.0001; MVIC: r=.51, P≤.0001; percent predicted FVC: r=.40, P≤.02; ALSFRS-R: r=.52, P≤.0001; ALSFRS-R gross motor subscore: r=.61, P≤.0001). In stage II, the 6MWT correlated with the 25FWT (r=−.83, P≤.0001), TUG test (r=−.77, P≤.0001), MVIC (r=.47, P≤.0001), and ALSFRS gross motor subscore (r=.61, P≤.0001), but not with percent predicted FVC (r=.09, P≤.513) or ALSFRS-R (r=.21, P≤.141).
Conclusions
The 6MWT is a valid measure of walking capacity of ambulatory patients with ALS that
is associated with measures of lower extremity muscle strength and function in both
stages of ambulation. The discordance between the 6MWT with the ALSFRS-R and percent
predicted FVC in stage II ambulatory patients with ALS indicates that the 6MWT is
an independent measure of ambulatory function in both stages of ambulation. The 6MWT
may provide a quantitative, simple, and inexpensive outcome measure of walking capacity
for early stage clinical trials in ambulatory patients with ALS.
Keywords
List of abbreviations:
6MWT (6-minute walk test), 25FWT (25-foot walk test), ALS (amyotrophic lateral sclerosis), ALSFRS-R (ALS Functional Rating Scale-Revised), FVC (forced vital capacity), MVIC (maximum voluntary isometric contraction), TUG (Timed Up and Go)To read this article in full you will need to make a payment
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Article Info
Publication History
Published online: April 29, 2017
Footnotes
Supported by the Carolinas ALS Research Fund (grant no. 2803), Carolinas Healthcare Foundation (grant no. 2781), and Muscular Dystrophy Association ALS Division (grant no. 2784).
Disclosures: none.
Identification
Copyright
© 2017 by the American Congress of Rehabilitation Medicine
