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A blood test has been developed that can predict whether Covid patients will need intensive care, or if they are likely to survive, soon after symptoms develop.
If validated in real-life hospital settings, the test could allow clinicians to target life-saving treatment to patients in greatest need first, increasing their chances of survival. It could also boost physicians’ confidence in difficult decisions, such as offering palliative care or an ICU bed when hospitals are close to capacity.
Earlier this year, Markus Ralser and his colleagues identified 27 proteins in the blood of Covid-19 patients that were present at different levels based on the severity of their symptoms. Since then, they have followed 160 Covid patients whose blood was tested when they entered the hospital to explore whether their protein signature could predict the progression of their disease.
The idea is to give doctors a “digital picture” of how sick a patient is, something that you can’t necessarily tell just by looking at them, which could help inform their treatment. For example, in Covid-19, a phenomenon called happy hypoxia means that a patient may feel relatively well but then deteriorate rapidly.
“It turns out that these patients have an early inflammatory response to infection, which we can measure in the blood and use to say, ‘Okay, 40 days later, this is your likely outcome,’” said Ralser, a professor of biochemistry at the Francis Crick Institute in London and the Charité University Medicine in Berlin.
“Every day they have severe Covid, and people who need intensive care should receive it as soon as possible because this greatly increases their chances of survival.”
Although it is unlikely that a blood test alone will ever be used to determine which patients are assigned the few beds in the intensive care unit, it could provide additional data to help inform physicians making these difficult decisions.
Proteins were measured using an instrument called a mass spectrometer, which can detect the presence and abundance of hundreds to thousands of proteins in a sample, based on their mass.
Such proteomic analysis allows many more proteins to be measured in the blood than with current clinical trials, according to Manuel Mayr, professor of cardiovascular proteomics at the British Heart Foundation at King’s College London, who was not involved in the study. “This can reveal important information about why some Covid-19 patients may have a better or worse prognosis,” he added.
So far, the test has been validated in 24 other seriously ill patients, where it correctly predicted the outcome of 18 of the 19 who survived and five of the five patients who died.
“We can predict which patients will need oxygen support and ventilator support quite accurately, and we also have markers for patients who are not as seriously ill at first but are at high risk of getting worse,” said Ralser, whose research is published as a pre-press, but not yet peer reviewed.
The next step is to validate the test in hospitals in the UK, US and Germany. These studies are expected to begin in the next few weeks, and the data from them would have to be sent to health regulators later, before the tests are more available.
Mayr cautions that such studies can lead to additional complications, as age and medical treatments can also influence the types and abundance of proteins that circulate in the blood.
“In this study, samples were collected at the beginning of the pandemic, at a time when patients were not receiving dexamethasone, a drug that suppresses the immune response and has now become the standard of care and reduces the risk of death in patients with severe Covid -19, “he said. “Therefore, these new protein markers will require further testing in larger, independent cohorts of Covid-19 patients receiving the latest medical treatment.”
It is also developing proteomic tests for Covid-19 to inform the prognosis of seriously ill patients: “In addition to proteins, we look at the RNA of the virus circulating in the blood as a predictor of a poor outcome. Viral load and the spread of viral material in the blood can be informative for the prognosis, especially in patients with severe Covid-19 admitted to intensive care ”.
Even if Covid vaccines mean our hospitals are better off by the time such tests are approved, these studies could pave the way for a broader use of proteomics within the NHS, with applications that go far beyond Covid- 19. For example, other researchers are developing proteomic tests to predict outcomes for patients with cancer, type 2 diabetes, and neurodegenerative diseases, including Alzheimer’s disease.
