Sub-maximal exercise testing in the assessment of
interstitial lung disease secondary to systemic
sclerosis: Reproducibility and correlations of the six
minute walk test
Maya H Buch 1, Christopher P Denton 2, Daniel E Furst 3, Loic Guillevin 4, Lewis J Rubin 5, Athol U Wells 6, Marco Matucci-Cerinic 7, Gabriela Riemekasten 8, Paul Emery 9, Harbajan Chadha-Boreham 10, Pascal Charef 10, Sebastien Roux 10, Carol M Black 2 and James R Seibold 1*
1 University of Michigan, United States
2 Royal Free and University College Medical School, United Kingdom
3 UCLA School of Medicine, University of California, United States
4 Universite Rene Descartes, Paris, France
5 University of California, San Diego, United States
6 Royal Brompton Hospital, United Kingdom
7 University of Florence, Italy
8 Charite University Hospital, Berlin, Germany
9 University of Leeds, United Kingdom
10 Actelion, Switzerland
* To whom correspondence should be addressed. E-mail: jseibold{at}umich.edu.
Accepted 15 July 2006
 | Abstract |
|---|
Introduction: The six-minute walk test (6MWT) is
increasingly utilised as an outcome measure in
interstitial lung disease (ILD). The purpose of this
study was to evaluate the usefulness of the 6MWT in a
cohort of patients with ILD secondary to scleroderma
(SSc) and to correlate with established physiological
parameters.
Methods: 163 patients with SSc-ILD were recruited
for a multi-centre, randomised, double-blind clinical
trial. Available data at protocol screening included
repeated six minute walk tests (6MWT), pulmonary
function testing with diffusing capacity, Doppler
echocardiography and high resolution computed tomography
thorax. Borg dyspnoea index was evaluated pre- and post
6MWT.
Results: Mean distance walked during walk test 1
was 396.6m (SD 84.55m) compared with a mean of 399.5m
(SD 86.28m) at walk test 2. The within subject, inter-
test correlation as determined by Pearson correlation
coefficient testing was 0.95 (p<0.0005). However, there
were only weak correlations of 6MWT with percent forced
vital capacity and the Borg dyspnoea index and no
correlation was observed with percent diffusing capacity.
Conclusion: 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 interstitial lung disease suggests a multi-
factorial basis for limited exercise capacity in SSc and
calls into question the utility of the 6MWT as a measure
of outcome in future studies of SSc-ILD.
Keywords:
interstitial lung disease, scleroderma, six minute walk test, sub-maximal exercise test
