Impact of COVID-19 pneumonia on interstitial lung disease: semi-quantitative evaluation with computed tomography

Abstract

Objectives: To evaluate the CT scores and fibrotic pattern changes in interstitial lung disease (ILD) patients, with and without previous COVID-19 pneumonia.

Methods: Patients with ILD (idiopathic pulmonary fibrosis (IPF) and connective tissue disease-associated ILD (CTD-ILD)) were retrospectively enrolled in the study which consisted of patients who had COVID-19 pneumonia while the control group had not. All patients had two CT scans, initial and follow-up, which were evaluated semi-quantitatively for severity, extent, and total CT scores, fibrosis patterns, and traction bronchiectasis.

Results: A total of 102 patients (pneumonia group n = 48; control group n = 54) were enrolled in the study. For both groups, baseline characteristics were similar and CT scores were increased. While there was a 4.5 ± 4.6 point change in the total CT score of the COVID-19 group, there was a 1.2 ± 2.7 point change in the control group (p < 0.001). In the IPF subgroup, the change in total CT score was 7.0 points (95% CI: 4.1 to 9.9) in the COVID-19 group and 2.1 points (95% CI: 0.8 to 3.4) in the control group. Seven patients (14.6%) in the COVID-19 group progressed to a higher fibrosis pattern, but none in the control group.

Conclusions: Semi-quantitative chest CT scores in ILD patients demonstrated a significant increase after having COVID-19 pneumonia compared to ILD patients who had not had COVID-19 pneumonia. The increase in CT scores was more prominent in the IPF subgroup. There was also a worsening in the fibrosis pattern in the COVID-19 group.

Key points: • The impact of COVID-19 pneumonia on existing interstitial lung diseases and fibrosis is unclear. • COVID-19 pneumonia may worsen existing interstitial lung involvement with direct lung damage and indirect inflammatory effect. • COVID-19 pneumonia may affect existing lung fibrosis by triggering inflammatory pathways.

Keywords: COVID-19; Fibrosis; Interstitial lung disease; Multidetector computed tomography; Pneumonia.

Fig. 1

Participant flow diagram for the COVID-19 group. ILD, interstitial lung disease; IPF, idiopathic pulmonary fibrosis; CTD-ILD, connective tissue disease-associated ILD

Fig. 2

Distribution of total scores of PCR positive and negative patients according to initial and follow-up CTs

Fig. 3

a Distribution of total scores of patients according to initial and follow-up CTs in the COVID-19 group, with or without IPF. b Distribution of total scores of patients according to initial and follow-up CTs in the control group, with or without IPF

Fig. 4

A 64-year-old man with idiopathic pulmonary fibrosis (IPF) presenting with progressive dyspnea after COVID-19 pneumonia. a Baseline CT images obtained 2 months before COVID-19 pneumonia show peripheral reticulations and minimal traction bronchiectasis (arrow) in the lower lobes consistent with a probable UIP pattern. The Warrick CT scores were; severity score:6, extent score:9, total score: 15. b Follow-up CT images obtained 8 months after COVID-19 pneumonia show more prominent traction bronchiectasis and new subpleural cyst (arrow). The Warrick CT scores were progressed in the follow-up images; severity score:11, extent score:12, total score: 23