Clinical and Radiological Outcomes of Organising Pneumonia Secondary to COVID-19: A 2-Year Longitudinal Cohort Study

Background: Organising pneumonia secondary to COVID-19 (OP-COVID-19) is a recognised inflammatory complication of SARS-CoV-2 infection. We assessed the 2-year clinical, radiological, and functional evolution of patients hospitalised with OP-COVID-19 and identified factors independently associated with long-term fibrotic-like lesions. Methods: This ambispective longitudinal study included adults consecutively hospitalised with OP-COVID-19 from March 2020 to February 2021. Diagnosis was based on clinical assessment and high-resolution computed tomography (HRCT). Patients underwent standardised follow-up at 3, 6, 12, and 24 months after hospital discharge, including clinical assessment, chest HRCT, pulmonary function tests, and the six-minute walk test. Longitudinal radiological changes were assessed using paired comparisons, and exploratory multivariable logistic regression identified factors independently associated with long-term fibrotic-like lesions. Results: OP-COVID-19 was diagnosed in 271 patients (4.9%), and 228 were included in the follow-up cohort. Inflammatory HRCT abnormalities resolved progressively, with paired comparisons showing a significant reduction in consolidations, peribronchovascular opacities, crazy-paving pattern, reversed halo sign, and perilobular opacities at 3-6 months compared with the initial HRCT (p < 0.05 for all). Among the 221 patients with an ascertainable final radiological outcome, persistent pulmonary abnormalities were observed in 14.9%, including fibrotic-like lesions in 10.4%. No statistically detectable late radiological progression was observed among patients undergoing extended imaging follow-up. The need for respiratory support during the acute phase (odds ratio [OR] 5.79, 95% confidence interval [CI] 1.81-18.52), bronchial dilatation (OR 3.50, 95% CI 1.10-11.11), and architectural distortion and/or volume loss on initial HRCT (OR 4.72, 95% CI 1.80-12.35) were independently associated with long-term fibrotic-like abnormalities. Pulmonary function was largely preserved, with mildly reduced diffusing capacity for carbon monoxide (DLCO) in the assessed subsets. Conclusions: OP-COVID-19 has a favourable long-term prognosis, with progressive resolution of inflammatory abnormalities in most patients. Fibrotic-like lesions occur in a minority of patients and are associated with greater initial disease severity and early structural abnormalities on HRCT. These findings support risk-stratified follow-up for patients with OP-COVID-19.