Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Validation of 6 Minute Walking Distance in Patients with Pulmonary Arterial Hypertension Associated with Systemic Sclerosis.

Huscher11,  Dörte, Roubinis17,  Nicholas, Avouac18,  Jerome, Behrens10,  Frank, Denton1,  Christopher P., Furst8,  Daniel E., Foeldvari14,  Ivan

Centre for Rheumatology, Royal Free Campus, University College Medical School, London, United Kingdom
Division of Rheumatology/ZAFES, J.W. Goethe University, Frankfurt, Germany
German Rheumatism Research Centre, Berlin, Germany
Hannover Medical School, Department of Pneumology, Hannover, Germany
Institute for Clinical Pharmacology, Medical Faculty, Technical University, Dresden, Germany
Pediatric Rheumatology Clinic, General Hospital Eilbek, Germany
Pfizer Ltd, Sandwich, UK
Pfizer Ltd, Tadworth, UK
Quanticate Ltd, Hitchin, UK
Rheumatology A Department, RDU, Paris, France
Service de Pneumologie et Reanimation Respiratoire, Centre des Maladies Vasculaires Pulmonaires, Hopital Antoine-Beclere, Université Paris-Sud, Clamart, France
Department of Internal Medicine, DRK-Kliniken Berlin Köpenick, Berlin, Germany
Department of Medicine, Division of Rheumatology, Denothe Center, University of Florence, Italy
Department of Rheumatology and Internal Medicine, Medical University of Bialystok, Poland
Department of Rheumatology, University Hospital Zurich, Zurich, Switzerland
Dept. of Medicine, University of Queensland, Queensland, Australia
Division of Pulmonary and Critical Care Medicine, University of California, San Diego School of Medicine, La Jolla
Division of Rheumatology, Department of Medicine, David Geffen School at UCLA, Los Angeles, CA
Division of Rheumatology, University of Connecticut, Farmington, CT

Objective:

To validate 6 minute walking distance (6MWD) as an outcome measure in patients with pulmonary arterial hypertension associated with systemic sclerosis (PAH-SSc) using the OMERACT filter of truth, discrimination and feasibility.

Methods:

6MWD was validated in PAH-SSc patients using data from randomized controlled clinical trials (SUPER-1 and STRIDE-1) and from an observational registry (CompERA-XL) reflecting clinical practice. All patients had PAH confirmed by right heart catheterization (RHC). Databases were assessed for the different aspects of the OMERACT filter. 6MWD was compared to pulmonary vascular resistance (PVR) obtained by RHC as the gold standard.

Results:

A total of 57 PAH-SSc patients from trial data were available. Analysis of registry data was restricted to PAH-SSc patients where documented PVR and 6MWD were measured within a 30-day span (n=61) to allow for correlation analysis. In trials, both measurements were taken within 4 days. Regarding criterion validity, a linear correlation between 6MWD and PVR of -0.28 was found in the trials, -0.36 in the observational data. In trial data, 6MWD partially correlated with PVR in patients with moderate (500<=PVR<800; r=-0.28) and severe (PVR>=800; r=-0.33) but not in mild (PVR<500; r=-0.03) SSc-PAH. Change in 6MWD after 12 weeks of treatment correlated with change in PVR in the trials (r=-0.25). Regarding construct validity, 6MWD partially correlated with relevant dimensions of the SF-36 (e.g. physical functioning r>0.33) in the trials, and discriminated for NYHA class and Borg index for both trial and observational data. Available data did not allow a reliable assessment of sensitivity to change over time (in placebo or untreated patients) or an assessment of reliability.

In comparison, 398 trial patients and 314 registry patients with IPAH were analyzed. Linear correlation of 6MWD and PVR was small (r=-0.22, r=-0.06). Correlation was better in mild and moderate than severe IPAH. Correlation of changes 12 weeks after treatment start was low (r=-0.12). 6MWD correlated with physical functioning of the SF36 (r>0.45), and showed discriminating value for Borg index in both cohorts, for NYHA class only in trial data.

Conclusion:

6MWD and PVR have both demonstrated clinical utility in evaluating patients with PAH, but their relationship is unclear. Assessed by linear correlation between 6MWD and PVR, we found weak criterion validity in these cohorts of PAH-SSc patients. Due to differing correlation patterns between different stages of severity we could show only partial content validity. Construct validity was confirmed by the discriminating value for NYHA class and Borg index. Trial data were confirmed by registry data on most points. Notably, there were no major differences between patients with SSc-PAH and IPAH for the assessed OMERACT criteria. Limitations of this analysis include the small sample size, and retrospective, post hoc analysis of pooled data from different trials. However, taken together these data illustrate limitations of 6MWD as a single outcome measure in SSc-PAH clinical trials or clinical practice.

*both authors contributed equally

To cite this abstract, please use the following information:
Huscher, Dörte, Roubinis, Nicholas, Avouac, Jerome, Behrens, Frank, Denton, Christopher P., Furst, Daniel E., et al; Validation of 6 Minute Walking Distance in Patients with Pulmonary Arterial Hypertension Associated with Systemic Sclerosis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :599
DOI: 10.1002/art.28367

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