Some patients who were infected with COVID-19 experience decreased lung function and respiratory symptoms even after recovery. The possibility of detecting this long-term risk of lung damage through blood tests has been suggested.
According to the PHOSP-COVID study involving researchers from the University of Leicester, Imperial College London, and University College London (UCL), analyzing specific molecular levels in the blood of patients who were hospitalized due to COVID-19 can provide clues to identify those at high risk of persistent lung abnormalities.
The PHOSP-COVID study is a large observational study led by the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre (BRC), which tracks the long-term effects of COVID-19 on patients' physical and mental health and recovery processes.
The researchers analyzed blood samples taken about five months after discharge from 957 patients who were hospitalized due to COVID-19, measuring various biomarkers known to increase in cases of lung damage. The analyzed molecules include KL-6 (Krebs von den Lungen-6), MMP-7 (matrix metalloproteinase-7), SP-D (surfactant protein-D), and SP-A (surfactant protein-A).
Among these, patients with confirmed lung abnormalities on chest CT scans had significantly higher levels of KL-6 and MMP-7. These two substances are known to increase in patients with existing lung diseases and are interpreted as indicators reflecting damage to the epithelial cells lining the inside of the lungs.
Dr. Rachel Evans, a clinical lecturer at the University of Leicester, stated, "Epithelial cells are an important barrier surrounding the lungs, serving as a defense against particles we inhale and inducing mucus production and immune responses," adding, "The indicators found in the blood in this study show that this protective barrier has been damaged." She further explained that this damage affects "the persistent symptoms and decreased lung function in some long COVID patients."
She continued, "If we can identify who is likely to experience ongoing lung issues through a simple blood test, it could help develop more appropriate treatment strategies for each patient."
Dr. Ian Stewart from the National Heart and Lung Institute at Imperial College London, who led the analysis, emphasized, "The PHOSP-COVID study has secured high-quality data from many individuals, allowing us to identify signs of persistent lung damage even in relatively small groups," adding, "Given that such damage could have lifelong effects, it is important to find reliable indicators to distinguish at-risk groups."
Professor Gisli Jenkins from Imperial College London evaluated, "These results show the potential to screen for individuals at high risk of chronic lung disease after acute COVID-19 infection through blood tests." Professor Rachel Chambers from UCL also stated, "This study represents significant progress in finding reliable biomarkers that can be used to track and manage ongoing lung damage."
The researchers confirmed that the residual lung abnormalities appearing after COVID-19 are associated with increased signals of epithelial cell damage and fibrosis, stating that further research is needed to closely track whether these indicator changes recover over time or progress to lung fibrosis.
The results of this study were published in the international journal 《EBioMedicine》 under the title 'Residual lung abnormality following COVID-19 hospitalization is characterised by biomarkers of epithelial injury.'
