Background Patients with systemic sclerosis (SSc) often have a reduced aerobic capacity (1) and lung function (1, 2). To our knowledge it has not previously been investigated if lung function and aerobic capacity is associated with limited cutaneous (lcSSc) and/or diffuse cutaneous (dcSSc) and/or with positivity/negativity for anti-centromere antibodies (ACA) and/or anti-topoisomerase-I antibodies (ATA).
Objectives To evaluate how patients with lcSSc versus dcSSc and patients with different autoantibody profiles differed with regard to forced vital capacity (FVC), diffusion capacity of the lung for carbon monoxide (DLCO%) and aerobic capacity (ml/kg/min).
Methods Patients registered at the Karolinska University Hospital, Sweden, diagnosed with SSc (n=153) were included, 125 were females, mean age was 60±SD 12.9 years. Mean modified Rodnan skin score was 7.4±6. FVC and DCLO were investigated with spirometry and aerobic capacity with either of two tests: Åstrand's submaximal ergometer bicycle test (Å-test) or an 8-minute treadmill test.
Results The whole SSc-group had mean FVC 84±18% and DLCO 72±19% of predicted values. There were no differences in FVC and DLCO between patients with dcSSc (n=27) and lcSSc (n=126). ACA+ patients (n=57) had a higher FVC% 90±17 compared with ACA- patients (n=96) 80±17, (p=0.002). This difference was also true for DLCO%, ACA+ 78±19 compared to ACA- 69±18, (p=0.01). On the contrary, ATA+ patients (n=35) had lower FVC% 77±21 compared to ATA-(n=118) 86±16, (p=0.008) and DLCO% 64±22 and 74±17, (p=0.025). The whole SSc-group had “somewhat low” to “average” aerobic capacity assessed by the Å-test (n=43) 28±8 or treadmill test (n=43) 25±5 VO2 ml/kg/min, respectively. There were no differences in aerobic capacity between lcSSc and dcSSc or between patients with ACA +/- and ATA +/-. Due to arrhythmia and/or severe dyspnea 40 patients could not perform the Å-test, which was the primary test, or the treadmill test, n=13 and 14 patients could not perform any test due to low physical capacity or malfunctioning test equipment.
Conclusions This study indicates that ACA+ and ATA- patients have a better lung function compared with ACA- or ATA+ patients, as measured by FVC% and DLCO%. But this difference does not seem to influence the results on the aerobic capacity tests. However, patients experienced difficulties to complete our aerobic capacity tests. Our results also indicate that the antibody profile might predict lung function and that it is important to assess FVC and DCLO in these patients. More research is needed to understand how to test aerobic capacity in these patients.
Someya F, Mugii N, Yahata T, Nakagawa T. Exercise capacity in relation to autoantibodies in systemic sclerosis patients. Rheumatology international. 2013 Nov;33(11):2913-6.
Meier FM, Frommer KW, Dinser R, Walker UA, Czirjak L, Denton CP, et al. Update on the profile of the EUSTAR cohort: an analysis of the EULAR Scleroderma Trials and Research group database. Annals of the rheumatic diseases. 2012 Aug;71(8):1355-60.
Disclosure of Interest None declared