High Resolution Computed Tomography Findings of Pulmonary Fibrosis in COVID-19 Survivors and its Association with Inflammatory Markers- A Retrospective Study

Introduction: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection enters human body through respiratory tract and then rapidly spread to involve lungs and multiply swiftly leading to severe hypoxic pneumonia. Clinically, Coronavirus Disease-2019 (COVID-19) infection is identified by three stages based on viral infection, lung involvement with inflammation and pulmonary fibrosis. High resolution Computed Tomography (HRCT) lung play an important role in diagnosis and management of lung fibrosis in coronavirus disease patients.

Aim: To study association between inflammatory markers and development of lung fibrosis in post COVID-19 patients. Study also aimed at assessment of chest Computed Tomography (CT) Involvement Score (CT-IS) and COVID-19 Reporting and Data System (CO-RADS) for chest CT in post COVID patients presented with lung fibrosis.

Materials and Methods: This retrospective study included elaborate evaluation of HRCT findings and inflammatory markers of 54 patients presented with pulmonary fibrosis at tertiary care centre for duration of six months from 1st June to 30th November 2020. Only those patients were included in which both HRCT findings and clinical laboratory parameters were available. Interleukin-6 (IL-6), C-Reactive Protein (CRP), serum ferritin, Lactate Dehydrogenase (LDH), Erythrocyte Sedimentation Rate (ESR) and Procalcitonin (PCT) markers were studied. Statistical analysis was conducted using Chi-square test to compare the inflammatory markers with CT-IS score with p-value <0.05 was considered significant.

Results: Total 536 COVID positive patients were admitted in hospital and underwent HRCT lung from June 2020 to November 2020. Out of 536, 54 (10.07%) patients showed findings of lung fibrosis on follow-up CT scan. Among 54 patients with lung fibrosis, CRP, serum ferritin and IL-6 levels were high in 46 (85.19%), 42 (77.77%) and 48 (88.89%) patients respectively. Lactate dehydrogenase, ESR and PCT were increased in 12 (22.22%), 15 (27.78%) and 06 (11.11%) patients respectively. These levels were higher in fibrotic phase compared to prefibrotic phase. Erythrocyte sedimentation rate was significantly associated with the severity of lung fibrosis, having significant p-value=0.004.

Conclusion: Among all inflammatory markers, ESR value may be useful as a surrogate marker to predict the pulmonary fibrosis in COVID-19 patients. C-reactive protein, IL-6, LDH, serum ferritin and PCT levels do not show significant association with lung fibrosis on HRCT scan.