Secondary Organising Pneumonia among COVID-19 patients: a retrospective case control study

Abstract

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Since its appearance, there have been several reports of cases of Secondary Organising Pneumonia (SOP) induced by SARS-CoV-2. We aimed to evaluate the prevalence of SOP among hospitalised patients with COVID-19 pneumonia and to assess if disease severity, and other clinical factors and comorbidities are correlated with SOP development. We conducted a retrospective case-control study including hospitalised patients due to COVID-19 who performed a chest CT-scan during hospitalisation and compared patients with clinical and radiological evidence of SOP to patients without evidence of SOP. Demographics, comorbidities, disease severity, dexamethasone / remdesivir treatment, laboratorial results and outcomes were compared between groups. 115 patients were included, of whom 48 (41.7%) fulfilled clinical and imaging criteria for SOP. Among SOP patients, the most common chest CT-scan findings were consolidations, arciform condensations, and subpleural bands. SOP patients had longer hospitalisation (19.5 vs 10 days), but no significant differences in readmittance or mortality rates comparing to controls. In the adjusted effects model, the need for supplementary oxygen on the 21st day after symptom onset, the presence of OSCI = 4, when compared to OSCI ≤ 3, and higher C-reactive protein on admission, were significantly associated with higher odds for SOP. No other differences were identified between SOP and controls after adjusting for other factors. The use of Remdesivir or dexamethasone did not impact the diagnosis of SOP. Only 38% of SOP patients required specific treatment with high-dose corticosteroids. In conclusion, SARS-CoV-2 induced SOP may be more frequent than previously thought, especially among hospitalised patients. SOP may be more common in patients with a more severe disease, particularly those who fail to improve after the 2nd week of disease or who present higher inflammatory markers on admission. It increases the length of stay, but not all patients require specific treatment and may improve despite the absence of high dose corticosteroid treatment.