How COVID-19 Is Helping Research Into Pulmonary Fibrosis?
The interstitial lung diseases (ILDs) are a group of over 200 different diseases that may result in lung inflammation or (in the worst case) pulmonary fibrosis (PF). There are many different aetiologies for ILD/PF and in some cases, we do not know the cause, so called ‘idiopathic’.
One of the questions that we at Breathing Matters want to answer is – can COVID-19 give you pulmonary fibrosis? There are a few clues that this might be the case. Other coronaviruses such as Severe Acute Respiratory Syndrome (SARS) or Middle East Respiratory Syndrome (MERS) have been reported to cause PF in a small percentage of patients, but of course the numbers of patients affected by SARS-CoV-2, the virus that causes COVID-19, will be much greater so, even if only a small percentage are affected, the numbers may still be very large. The diagnosis of ILD/PF is suggested by a clinical finding of breathlessness and abnormal lung function. The diagnosis is then confirmed with a CT scan of the chest.
Initial studies from China, Italy and the UK have remarkably similar findings. Of patients with COVID-19 discharged from a hospital in China, nearly half had abnormal lung function (Mo X, et al. European Respiratory Journal 55: 2001217, 2020). Data from Leeds of patients with COVID-19 discharged from hospital showed that the majority (75% of those admitted to intensive care, and 65% of those admitted to the regular wards) still suffered from fatigue at 6 to 8 weeks post discharge. The number suffering from continual breathlessness was also high (70% of those admitted to intensive care, and 45% of those admitted to the ward). (Halpin S et al. Journal Medical Virology, First published: 30 July 2020, DOI: (10.1002/jmv.26368).An Italian study from Rome found that at 60 days around 55% of patients were suffering from fatigue and 40% from breathlessness. It is unclear what is the cause of these high levels of breathlessness, but a study from Austria is following their patients up in more detail at 6, 12 and 24 weeks after discharge. So far, they have found that at 6 weeks 47% of patients are short of breath and this falls to 39% at 12 weeks. In addition, 33% have abnormal lung function suggestive of lung fibrosis, but this falls to 22% at 12 weeks. Of course, to diagnose lung fibrosis requires at CT scan of the chest and they found that CT scans suggested an interstitial lung disease (ILD) or lung fibrosis in 88% falling to 56% at 12 weeks. However, it is also important to know how much of the lung is affected, and many of the studies do not clarify this, but just comment on whether ILD is present or not. The result is that it is hard to know whether these patients had minimal or significant ILD changes on the CT scan. Clearly, Breathing Matters will be looking out for the 24 week data.
Our own experience is that of around 800 patients seen at UCLH with COVID-19, in the first wave approximately 4-6% have persistent or slowly resolving CT changes at 12 months suggestive of interstitial lung involvement. The incidence of ILD may be less in subsequent waves because of the wider use of the steroid, dexamethasone, in patients with COVID-19 pneumonitis. Currently, our main priority is to analyse the scans of 20,000 patients who were hospitalised with COVID-19 and are taking part in the national PHOSP study, to see how common the development of ILD/ PF is in a much larger group of patients. We will also look at 10,000 patients who had COVID-19 but were not hospitalised. This study funded by UKRI is a multicentre study that will look at the incidence of post COVID-ILD, investigate how much of the lung is affected and what the critical contributory factors are. It may be that this virus and the enormous numbers of patients that have been infected will shed some light on the pathogenesis of other ILD/PF diseases.