AB0495 THE RELATIVE CONTRIBUTIONS OF PULMONARY ARTERY SYSTOLIC PRESSURE (PASP) AND FORCED VITAL CAPACITY (FVC) TO FUNCTION AND HEALTH RELATED QUALITY OF LIFE (HRQOL) IN SYSTEMIC SCLEROSIS (SSC)

M. Baron¹, M. Hudson¹, E. Sutton², J. Markland³, J. Pope⁴, D. Robinson⁵, N. Jones⁶, P. Docherty⁷, M. Abu-Hakima⁸, S. Leclercq⁹, D. Smith¹⁰, J. Mathieu¹¹
¹Rheumatology, McGill University, Montreal, ²Rheumatology, Dalhousie University, Halifax, ³Rheumatology, Universityof Sasketchewan, Saskatoon, ⁴Rheumatology, University of Western ontario, London, ⁵Rheumatology, Unioversity of Manitoba, Winnipeg, ⁶Rheumatology, University of Alberta, Edmonton, ⁷Rheumatology, 135 MacBeath St., Moncton, ⁸Rheumatology, University of Calgary, c, ⁹Rheumatology, University of Calgary, Calgary, ¹⁰Rheumatology, University of Ottawa, Ottawa, ¹¹Rheumatology, University of Montreal, Montreal, Canada

Background: Pulmonary Artery Hypertension (PAH) and interstitial lung disease (ILD) are common in SSc. The exact contribution of each to function and HRQoL in SSc has not been carefully studied.
Objectives: To determine the relative contributions of PAH and ILD to function and HRQoL in SSc.
Methods: The Canadian Scleroderma Research Group collects prospective data on adult patients with SSc. The diagnosis is confirmed by the participating rheumatologist. Patients complete detailed questionnaires which include the Stanford Health Assessment Questionnaire Disability Index (HAQ-DI) assessing physical functioning, the World Health Organization Disability Assessment Schedule II (WHODAS II) and the Medical Outcomes Study Short Form Version 2 (SF 36) measuring HRQoL. Disease severity is assessed with the scale developed by Medsger et al.¹. A severity score of 0 (normal) to 4 (end-stage) was generated for each of 9 systems. The worst category was scored for each system and results of any investigation not requested by the physician, therefore missing, were considered "normal". To derive a total disease severity score (DSS), the sum of the individual system scores was obtained but for the purposes of this study the pulmonary system was omitted as it includes data from both the FVC and the PASP. Echocardiograms and standard pulmonary function tests are performed on all patients. Correlation coefficients were performed with Kendall's tau b. Multiple linear regression used a forced entry method with disease duration, age, gender, PASP, FVC and DSS as independent variables. P < 0.05 was considered significant.
Results: 398 patients were included in the analysis. The PASP correlated with the HAQ (kendall’s Tau B = 0.19 (p < 0.001), physical component of the SF-36 (kendall’s Tau B = - 0.20 (p < 0.001) and the WHODAS II (kendall’s Tau B = 0.15 (p < 0.001) but not with the mental component of the SF-36. In multiple regression analysis, however, neither PASP nor FVC were significant predictors of the SF-36 PCS, the HAQ or the WHODAS II when controlling for DSS. We assessed the contribution of PASP and FVC to the WHODAS II subscales. The FVC was associated with understanding and communicating, getting around, getting along with people and life activities. PASP was essentially unrelated to the subscales.

Conclusion: The degree of PAH correlates with function and HRQoL in univariate analysis but neither PAH nor the degree of ILD are strong predictors of these outcomes when controlling for disease severity in other organs. Although it is obvious from clinical practice that for patients with either severe PAH or ILD, lung disease may be an important cause of morbidity, in the average patient the degree of pulmonary involvement is not severe enough to interfere significantly with function or HRQoL. Disease severity outside the lung appears to be more important.
References: 1.Medsger TA, Jr., Silman AJ, Steen VD, et al. A disease severity scale for systemic sclerosis: development and testing. J Rheumatol 1999;26(10):2159-67.