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Imaging Features of Systemic Sclerosis-Associated Interstitial Lung Disease
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Reproducibility and Utility of the 6-minute Walk Test in Systemic Sclerosis
Grégory Pugnet1,2, Zora Marjanovic3,4, Christophe Deligny3,4
1From the Service de Médecine Interne, CHU Toulouse Purpan; Faculté de Médecine de Toulouse, Toulouse; Hématologie clinique et thérapie cellulaire, and Unité de Médecine Interne, Maladies Auto-immunes et Pathologie Vasculaire, UF 04, Centre de référence des maladies auto-immunes systémiques rares d'Ile-de-France, Filière (FAI2R), AP-HP, hôpital Saint-Antoine; Université Paris Diderot, Sorbonne Paris Cité, Paris, France; Service de médecine interne, Centre national de référence "Lupus, syndrome des antiphospholipides et autres maladies auto-immunes systémiques rares," Hôpital Pierre Zobda Quitman, CHU de Martinique, Fort de France, Martinique; Service de Médecine Interne et Maladies Infectieuses, CHU de Poitiers, Poitiers, France; Department of Cardiology, Department of Internal Medicine, and Department of Rheumatology, Ghent University Hospital, Ghent, Belgium. dominique.farge-bancel@aphp.fr pugnet.g@chu-toulouse.fr.
Objective:
To assess the reproducibility and the utility of the 6-minute walk test (6MWT) in systemic sclerosis (SSc).
Methods:
All patients with SSc who underwent at least two 6MWT within a minimum 3-month interval plus simultaneous routine clinical, biological, and functional evaluations were consecutively enrolled in this observational study over 6 years. Following American Thoracic Society guidelines, each 6MWT was repeated twice to assess the 6-minute walk distance (6MWD) reproducibility, with the highest value being reported for subsequent analysis.
Results:
Among 56 (38 female) included patients aged 46 ± SD 12.7 years, with 17 ± 10 modified Rodnan skin score (mRSS) and 1 ± 0.8 Scleroderma Health Assessment Questionnaire (SHAQ) at first referral, 277 6MWT evaluations (5 ± 3.9 6MWT per patient) were performed over 23 ± 22.5 months followup. Meanwhile, 8 deaths (87.5% SSc-related) occurred. The mean 6MWD absolute value was 457 ± 117 m with a 4 ± 2.2 mean Borg dyspnea score. The 6MWD intraclass correlation coefficient was 0.996 (95% CI 0.995-0.999, p < 0.0001). In multivariate linear regression analysis, these factors were independently associated with a lower 6MWD: sex (R2 = 0.47, p < 0.0001), mRSS (R2 = 0.47, p = 0.008), tendon friction rub (R2 = 0.47, p = 0.003), SHAQ (R2 = 0.47, p = 0.02), muscle disability score (R2 = 0.47, p = 0.03), DLCO% (R2 = 0.47, p = 0.0008), and left ventricular ejection fraction (R2 = 0.47, p = 0.006). The 6MWD at first referral was an independent predictor for the overall mortality (HR 0.99, 95% CI 0.988-0.999) and the SSc-related mortality (HR 0.99, 95% CI 0.988-0.999).
Conclusion:
We show strong reproducibility for the 6MWD and confirm the 6MWT utility to assess the overall prognosis of patients with SSc.
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