Assessment of interstitial lung disease in systemic sclerosis using oscillometric methods: a novel approach to respiratory assessment

OBJECTIVES: Cardiopulmonary involvement is the leading cause of mortality in SSc, and early detection of interstitial lung disease (ILD) is critical to improving outcomes. Conventional spirometry has limitations, whereas impulse oscillometry (IOS) could provide a non-invasive, effort-independent method to detect and monitor pulmonary involvement in these patients. We aimed to evaluate IOS parameters in SSc-ILD, comparing their performance with conventional spirometry. METHODS: This study assessed the detection of the presence and severity of ILD in SSc patients using conventional spirometry, diffusing lung capacity for carbon monoxide (DLCO), IOS, and high-resolution CT (HRCT). RESULTS: Among 66 SSc patients, ILD was identified in 62.1%, with 26 patients having extensive and 15 limited ILD on HRCT. IOS demonstrated higher mean resonant frequency (Fres) in ILD-positive patients than in ILD-negative patients (22.95 ± 5.47 vs 15.01 ± 6.01, P = 0.001). Fres was also significantly higher in extensive ILD than in limited ILD and ILD-negative groups (P = 0.001 and P = 0.011, respectively). ROC analysis demonstrated that Fres achieved comparatively better diagnostic accuracy for detecting extensive ILD [area under the curve (AUC): 0.841, cut-off: 22.35, sensitivity: 73.1%, specificity: 85%], outperforming forced vital capacity (FVC) (% predicted) and DLCO (% predicted). For limited ILD, Fres showed moderate diagnostic performance (AUC: 0.752, cut-off: 17.42, sensitivity: 80%, specificity: 64%). CONCLUSION: Our findings indicate that impulse oscillometry, particularly Fres, may provide a non-invasive and effort-independent approach to assessing interstitial lung disease in SSc. Fres appeared to be related to radiological ILD extent and showed some diagnostic value, including in cases less evident by conventional spirometry.