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

## TL;DR

This study examines lung function in Thai patients with systemic sclerosis, finding that a restrictive lung pattern is common and spirometry is a useful screening tool.

## Contribution

The study identifies the prevalence of restrictive pulmonary function in Thai systemic sclerosis patients and evaluates correlations with BMI and anti-Scl70 antibodies.

## Key findings

- Restrictive spirometry pattern was found in 78.8% of patients.
- DLCO correlated moderately with FVC and inversely with BMI.
- Anti-Scl70 presence did not correlate with pulmonary function patterns.

## Abstract

Interstitial lung fibrosis is a major cause of internal organ involvement 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. Clinical characteristics and PF were recorded and analyzed.

Of 211 SSc patients, 128 patients who underwent the PF test were enrolled; 102 (79.7%) were female. The mean (SD) age was 54.0 (12.5) years. 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), defined as FVC < 80% predicted, 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. Spirometry is a cost-effective screening tool for detecting SSc-related pulmonary involvement in resource-limited settings. However, the power of using demographic data and the presence of anti-Scl70 to determine the probability of pulmonary complications remains limited.