Pulmonary fibrosis- a COVID-19 aftermath

Kanikah Mehndiratta, MSc, University of Glasgow

COVID-19 (coronavirus disease 2019) pandemic due to the SARS-CoV 2 (severe acute respiratory syndrome) viral strain has posed a high concern worldwide. This is because of the associated high mortality and the devising of effective treatment strategies. It has been nothing short of devastating at the global level leading to a total of 37,82,940 deaths worldwide as of June 2021. The infection usually presents with atypical pneumonia with symptoms ranging from a minor cold to severe respiratory system disorders.

Serial thin-section chest computed tomography (CT) scans can help during diagnosis and progression of the disease, including responses to treatment by depicting abnormalities in the lung tissues. Despite the viral clearance, chronic impairment of the lungs can lead to fibrotic interstitial lung diseases, mainly pulmonary fibrosis. Persistent follow-up checks are essential for the evaluation of post-COVID-19 recovered patients for symptoms of pulmonary fibrosis. A recent study published in the Respiratory Research journal focuses on the development of pulmonary fibrosis in COVID-19 survivors to identify early warning signs.

Pulmonary Fibrosis:

Amongst radiological findings, patients mainly depict bilateral, peripheral, and basal ground glass hazy opacities showing areas of increased attenuation. Pulmonary fibrosis is usually idiopathic, bears a genetic predisposition, and more likely appears in older patients presenting with high comorbidities of COVID-19. It could also develop due to delaying of hospitalized care and in particular patients with high BMI and fever. Chronic inflammation of the lung tissues could be a part of the pathogenesis.

The disease is considered to be a chronic sequela of the ARDS (acute respiratory distress syndrome) and can develop as early as 1 week in the course. ARDS can develop in about 40% of COVID-19 patients and is characterized by diffused alveolar damage, with an initial acute inflammatory phase in the hyaline membranes and edema. This can lead to an organizing phase characterized by loose fibrosis mostly within alveolar septa and pulmonary hyperplasia (type-II). The final is the fibrotic phase, majorly due to the dysregulated immune mechanisms of the cytokines (IL-6 and TNF-a) and protease enzymes mainly VEGF and other metalloproteinases. While some patients may recover from this, others face collagen deposition and fibroblasts deposition, ultimately causing pulmonary fibrosis.

Methodology and Results:

The study was conducted on a sample of 462 COVID-19 patients admitted at a Shenzhen hospital between January to April 2020. About 457 of them got CT scans either during hospitalization or after recovering to check for pulmonary lesions. More than half of them were followed up between the next3-5 months after disease onset. Parenchymal bands and bronchiectasis are the most common scan features in all samples observed. In the first 3 months, more than 70% developed pulmonary fibrosis and less than 5% in total reversed the condition in the first 30 days itself. The common factors associated were age, fever, BMI, and procalcitonin which acts as a marker of systemic inflammation. The study helped in identifying risk factors through logistic- regression analysis and prediction models with an accuracy of 76%. The abnormal lung function did not differ significantly in the fibrotic and non-fibrotic groups.

Conclusion:

The prediction model had an average under the curve area of 0.84 for the prediction of persistent pulmonary fibrosis during early diagnosis in COVID-19 recovered patients. The study could help in developing intervention tools for targeting the condition. Research on clinical and laboratory biomarkers is essential to sub-group patients who have more chances of developing lung fibrosis and associated reduction in lung capacity. Anti-fibrotic therapy is also proving effective in animal studies in attenuation of lung function decline and improve life expectancy.

Also read: What causes post-concussion syndrome, now revealed!

References:

1. Li, X., Shen, C., Wang, L., Majumder, S., Zhang, D., Deen, M. J., Li, Y., Qing, L., Zhang, Y., Chen, C., Zou, R., Lan, J., Huang, L., Peng, C., Zeng, L., Liang, Y., Cao, M., Yang, Y., Yang, M., Tan, G., … Liu, Y. (2021). Pulmonary fibrosis and its related factors in discharged patients with new corona virus pneumonia: a cohort study. Respiratory research, 22(1), 203. https://doi.org/10.1186/s12931-021-01798-6
2. Vasarmidi, E., Tsitoura, E., Spandidos, D. A., Tzanakis, N., & Antoniou, K. M. (2020). Pulmonary fibrosis in the aftermath of the COVID-19 era (Review). Experimental and therapeutic medicine, 20(3), 2557–2560. https://doi.org/10.3892/etm.2020.8980

Author info:

Kanikah Mehndiratta is an avid researcher in the field of Genetics with a background in Biotechnology. She is a post-graduate from the University of Glasgow in their Medical Genetics and Genomics program. Currently, based in Chandigarh as a Scientific Writer, she involves herself mainly in projects related to neurological disorders. Outside of academics, she likes to read novels, travel and involves in volunteer work mostly.

LinkedIn profile- https://www.linkedin.com/in/kanikah-mehndiratta-301830171

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3.https://bioxone.in/news/worldnews/first-ever-genomic-analysis-on-the-african-swine-fever-virus/

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