Supplementary Material for: The Role of Pulmonary Function Testing and Lung Imaging in the Long-Term Follow-Up of Patients with COVID-19 Pneumonia Role of Pulmonary Function Tests and High-Resolution Computed Tomography in Post-COVID-19 Interstitial Lung Disease

Background: Post-COVID-19 Interstitial Lung Disease (PC-ILD) is characterized by fibrotic-like signs at high-resolution computed tomography (HRCT) and pulmonary function tests (PFTs) abnormalities after SARS-CoV-2 infection. It is still not clear how frequent these tests should be performed to rule out long-term consequences of COVID-19 pneumonia. Objectives: The aims of our study were to evaluate the incidence and risk factors of PC-ILD and possibly to propose a long-term follow-up program. Method: One-hundred patients, hospitalized in our ward for moderate to critical COVID-19, underwent two follow-up visits at three and 15 months in which PFTs and HRCT were performed. Results: At the 15-month follow-up, 8% of patients showed residual radiological and functional signs consistent with PC-ILD. All but one of these patients had already demonstrated PFTs and HRCT alterations at first follow-up visit, and the last 1 patient showed worsening of lung function during follow-up. These findings highlight the negative predictive value of PFTs at 3-month follow-up for the development of PC-ILD. Aging, severity of COVID-19, and degree of pulmonary involvement during acute infection proved to be significant risk factors for developing PC-ILD. Conclusions: Our study highlights the importance of PFTs in the long-term follow-up of patients affected by moderate to critical COVID-19 pneumonia. Further studies are needed to confirm our hypothesis that HRCT should be performed only in patients with PFTs abnormalities.