Scientists say levels of a specific protein in someone’s blood could predict whether they are at high risk of getting critically ill or dying of Covid.
Imperial College London experts say they have detected a blood protein which appears directly linked to the risk of death or severe illness.
The protein, named GM-CSF, is thought to be responsible for the immune system going haywire and causing organ damage or death in some people with Covid.
Finding it early on when a Covid patient is admitted to hospital might allow doctors to treat them more aggressively, and it is possible to target GM-CSF with existing drugs already used to treat arthritis.
Bringing levels down could reduce the risk of someone becoming gravely ill, the researchers said.
In a study of more than 500 people with coronavirus the team found that levels of the protein – known as a cytokine – were significantly higher in very ill people and almost 10 times higher in people who later died.
Professor Peter Openshaw, one of the experts behind the study, said: ‘These insights are crucial in improving our understanding and clinical management of Covid.’
The researchers are not yet at the stage where they could mass-produce a test, but said it was useful to be able to recognise the warning sign.
Imperial College London researchers have identified a cytokine – dubbed GM-CSK – that was at high levels early on in Covid patients that later suffered severe disease. Doctors say this could provide an early warning sign for which patients are more at risk from the virus
Blood samples were tested from 471 hospitalised Covid patients and 39 outpatients with a mild form of the disease in England.
Scientists also compared 20 historic samples from patients who had died from flu during the 2009/10 swine flu epidemic.
The samples were scanned for for 33 different types of cytokines.
Cytokines are released into the bloodstream when someone catches an infection – they are tiny substances that fire up the immune system to attack invaders.
Normally they help to ward off diseases but, if the blood contains too many of them at once, they can trigger an over-reaction called a ‘cytokine storm’.
This is a reaction in which the immune system over-reacts to danger; by causing widespread, uncontrolled swelling this can permanently damage healthy parts of the body and cause fatal problems with the internal organs.
In their blood screens the Imperial College London researchers found that GM-CSF was at high levels early on in patients that later suffered severe disease.
Doctors said this could provide an early warning for which patients are more at risk and pave the way for new treatments to combat the disease. But they said more research and tests were needed.
Dr Ryan Thwaites, from the National Heart and Lung Institute at Imperial, said: ‘GM-CSF appears to specifically mark out severe Covid-19 and may play a role in driving severe disease.
‘In future studies, we need to determine whether elevated levels of this protein in the blood at an early stage allows us to identify patients at increased risk of becoming very ill and may benefit most from receiving targeted treatments aimed at GM-CSF.’
Professor Peter Openshaw, an experimental medicine expert at the university, added: ‘These insights into the molecular drivers of disease are crucial in improving our understanding and clinical management of Covid-19…
‘We hope to inform the worldwide community of clinicians and investigators about where to look and what to target.’
Scientists said future treatments could suppress the amount of GM-CSF in the body, which they said may help alleviate severe disease and improve survival.
There are already two drugs available that can suppress this cytokine.
They are Sargramostim, which is typically used after a bone marrow transplant, and Otilimab, which treats multiple sclerosis and rheumatoid arthritis.
Both can help doctors to regulate the function of the immune system.
The study was carried out with the International Severe Acute Respiratory and emerging Infection Consortium (ISARIC) based in London.
But the researchers said the blood test wouldn’t be suitable for mass blood testing of everyone who was positive for coronavirus because it was too complex.
Dr Kenneth Baillie, an intensive care doctor at the University of Edinburgh who was involved in the research, said it would ‘not be useful’ to use blood tests en masse.
‘It would not be very useful to test patients at hospital when they’re already unwell,’ he said during a press briefing.
‘We don’t have the ability to test people at large scale to identify these types of risk factors, and testing who will be sick with Covid won’t be practical.
‘We need treatments that will turn this from a devastating disease into a treatable disease.’
The study was published in the journal Science Immunology.