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Submaximal exercise testing in the assessment of interstitial lung disease secondary to systemic sclerosis: reproducibility and correlations of the 6-min walk test
  1. M H Buch1,
  2. C P Denton2,
  3. D E Furst3,
  4. L Guillevin4,
  5. L J Rubin5,
  6. A U Wells6,
  7. M Matucci-Cerinic7,
  8. G Riemekasten8,
  9. P Emery9,
  10. H Chadha-Boreham10,
  11. P Charef10,
  12. S Roux10,
  13. C M Black2,
  14. J R Seibold1
  1. 1University of Michigan Scleroderma Program, University of Michigan Health System, Ann Arbor, Michigan, USA
  2. 2Centre for Rheumatology, Royal Free Campus, Royal Free and University College Medical School, London, UK
  3. 3Division of Rheumatology, UCLA School of Medicine, University of California, Los Angeles, California, USA
  4. 4Department of Internal Medicine, Hopital Cochin, Assistance Publique-Hopitaux de Paris, Universite Rene Descartes, Paris, France
  5. 5Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of California, San Diego, La Jolla, California, USA
  6. 6Interstitial Lung Disease Unit, Royal Brompton Hospital, Fulham, London, UK
  7. 7Division of Rheumatology, Department of Medicine, University of Florence, Florence, Italy
  8. 8Department of Rheumatology and Clinical Immunology, Charite University Hospital, Berlin, Germany
  9. 9Academic Unit of Musculoskeletal Disease, University of Leeds, Leeds, UK
  10. 10Actelion, Allschwil, Switzerland
  1. Correspondence to:
    Professor J R Seibold
    University of Michigan Scleroderma Program, 3918 Taubman Centre, Box 0358, 1500 E Medical Center Drive, Ann Arbor, MI 48109-0358, USA; jseibold{at}umich.edu

Abstract

Background: The 6-min walk test (6MWT) is increasingly used as an outcome measure in interstitial lung disease (ILD).

Aim: 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.

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 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.

  • 6MWT, six-min walk test
  • DLCO, single-breath diffusing capacity
  • FVC, forced vital capacity
  • HRCT, high-resolution computed tomography
  • IIP, idiopathic interstitial pneumonia
  • ILD, interstitial lung disease
  • OMERACT, outcome measures in rheumatological clinical trials
  • PAH, pulmonary arterial hypertension
  • SSc, systemic sclerosis

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Footnotes

  • Published Online First 25 July 2006

  • Funding: This study was supported by Actelion Pharmaceuticals, Allschwil, Switzerland. MHB and JRS were supported by the Jonathan and Lisa Rye Scleroderma Research Fund and the Linda Dolce Research Fund of the University of Michigan, Ann Arbor, Michigan, USA.

  • Competing interests: HC-B, PC and SR work for Actelion Pharmaceuticals. CPD, DEF, LG, LJR, AUW, MM-C, CMB and JRS are on the Actelion Steering Committee and have acted as advisors and investigators in clinical trials.

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