Objective: The aim of this study was to clarify the characteristics of pulmonary function tests (PFT), especially carbon monoxide diffusion capacity (DLCO), and their correlation with clinical features and immunological findings in patients with systemic lupus erythematosus (SLE).
Methodology: Vital capacity (VC) and DLCO were analysed retrospectively in 110 sequential Japanese SLE patients with active disease between 1985 and 1999. In 38 patients, serial measurements of PFT were also assessed during high-dose corticosteroid therapy.
Results: DLCO was reduced in 52 patients (47%) and a restrictive impairment of PFT was observed in nine patients (8%). The prevalence of pulmonary fibrosis was 13%. Reduced DLCO was frequently observed, even in patients with neither pulmonary fibrosis nor a restrictive pattern. No correlation between immunological data and reduced DLCO was found, except for the presence of anti-RNP. Patients with Raynaud's phenomenon showed a higher prevalence of DLCO impairment than those without this phenomenon. Although immunological parameters improved significantly after the corticosteroid therapy, no significant change in the level of DLCO was observed.
Conclusions: Impairment of DLCO was frequently observed in patients with SLE who had no clinical respiratory abnormalities. DLCO impairments were correlated with Raynaud's phenomenon clinically, and the presence of anti-RNP immunologically. No significant correlation was found between impairment of DLCO and disease activity of SLE.