Pulmonary function in Thai patients with systemic sclerosis; a single center 6-year retrospective study

Pulmonary involvement is a major cause of internal organ complication and the leading cause of death in patients with systemic sclerosis (SSc). This study aimed to demonstrate the characteristics of pulmonary function (PF) in Thai patients with SSc and the association between PF and body mass index (BMI) and anti-topoisomerase (anti-Scl70).

All patients diagnosed with SSc in our tertiary care teaching hospital database between 2016 and 2021 were reviewed and analyzed.

Of 211 SSc patients, 128 patients who underwent the PF test were enrolled; 102 (79.7%) were female. The mean age was 54 years. The median BMI for all patients was 21.7 kg/m ². Regarding anti-Scl70, 10.9% of patients were positive, 7.8% were negative, and the status was unreported for 81.3%. The mean (SD) forced expiratory volume in one second (FEV1) forced vital capacity (FVC) ratio was 0.8 (0.1). The mean (SD) % predicted values of FEV1, FVC, and diffusing capacity of the lungs for carbon monoxide (DLCO) were 76.3 (16.3), 69.1 (15.8), and 75.5 (22.8), respectively. A restrictive spirometry pattern (RSP) was found in 78.8% of the patients. DLCO had a moderate positive linear correlation with FVC (r=0.50, p <0.001) and a moderate negative linear correlation with BMI (r=-0.36, p <0.001). However, there was no correlation between FVC and BMI. There was no statistical difference in demographic data or the presence of anti-Scl70 among patients with or without RSP.

RSP is common among Thai patients with SSc. However, the power of using demographic data and the presence of anti-Scl70 to determine the probability of pulmonary involvement remains limited.