Role of impulse oscillometry together with diffusing capacity of the lungs for carbon monoxide and high-resolution computed tomography for the chest in early diagnosis of interstitial lung disease in patients with connective tissue diseases

Abstract Background Connective tissue diseases (CTDs) are systemic autoimmune disorders characterized by repeated lung involvement. Interstitial lung disease (ILD) can arise from nearly any CTD, imposing a significant burden on patients and strongly affecting their prognosis. Addressing the gaps in early diagnosis, monitoring, and treatment of these patients requires a comprehensive and multidisciplinary approach for optimal management. Aim To find the best modality for early diagnosis of ILD in patients with connective tissue disorders through the use of diffusing capacity of the lungs for carbon monoxide (DLCO), impulse oscillometry (IOS) and high-resolution computed tomography (HRCT) chest. Patients and methods This study was cross-sectional, analytical, and observational was conducted on 60 patients who were diagnosed with CTD, during the period from March 2022 to March 2023, who were admitted to Chest and Rheumatology Department or outpatient clinics visitors, to Ain Shams University Hospitals. Results The sensitivity of DLCO, HRCT, and IOS in detecting interstitial affection in CTD patients was 90, 81.5, and 72.2%, respectively. There is high statistical significance between DLCO and both CT chest and IOS in detecting ILD in CTD patients. There is a highly significant correlation between DLCO with Spirometric parameters (forced vital capacity, forced expiratory volume 1 s) and between DLCO with IOS parameters (actual ×5). Conclusion ILD should always be considered in patients with CTD. Diagnosis of CTD-ILD is challenging so early diagnosis of ILD using DLCO, HRCT chest or by using IOS is important as it could affect therapy plans.