Submaximal exercise testing in the assessment of interstitial lung disease secondary to systemic sclerosis: reproducibility and correlations of the 6-min walk test.
BACKGROUND
The 6-min walk test (6MWT) is increasingly used as an outcome measure in interstitial lung disease (ILD).


OBJECTIVE
To evaluate the usefulness of the 6MWT in a cohort of patients with ILD secondary to systemic sclerosis (SSc) and to correlate with established physiological parameters.


METHODS
163 patients with SSc-ILD were recruited for a multicentre, randomised, double-blind clinical trial. Available data at protocol screening included repeated 6MWTs, pulmonary function testing with diffusing capacity, Doppler echocardiography and high-resolution computed tomography of the thorax. Borg Dyspnoea Index was evaluated before and after 6MWT.


RESULTS
Mean (standard deviation (SD)) distance walked during walk test 1 was 396.6 (84.55) m compared with 399.5 (86.28) m at walk test 2. The within-subject, intertest correlation as determined by Pearson's correlation coefficient testing was 0.95 (p<0.001). However, only weak correlations of 6MWT with percentage forced vital capacity and the Borg Dyspnoea Index were observed, and no correlation was observed with percentage diffusing capacity.


CONCLUSIONS
These data confirm the high reproducibility of the 6MWT in patients with SSc-ILD and therefore the validity of the test in this cohort. The lack of correlation of 6MWT with standard physiological parameters of ILD suggests a multifactorial basis for limited exercise capacity in patients with SSc and calls into question the utility of the 6MWT as a measure of outcome in future studies on SSc-ILD.
Buch
M H
MH
University of Michigan Scleroderma Program, 3918 Taubman Centre, Box 0358, 1500 E Medical Center Drive, Ann Arbor, MI 48109-0358, USA.
Denton
C P
CP
Furst
D E
DE
Guillevin
L
L
Rubin
L J
LJ
Wells
A U
AU
Matucci-Cerinic
M
M
Riemekasten
G
G
Emery
P
P
Chadha-Boreham
H
H
Charef
P
P
Roux
S
S
Black
C M
CM
Seibold
J R
JR
D000328:Adult; D004417:Dyspnea / Q000175:diagnosis; D005080:Exercise Test / Q000379:methods* / Q000706:statistics & numerical data; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology; D017563:Lung Diseases, Interstitial / Q000175:diagnosis* / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D012129:Respiratory Function Tests; D012595:Scleroderma, Systemic / Q000150:complications* / Q000503:physiopathology; D012680:Sensitivity and Specificity; D016138:Walking