According to current study, a blood test conducted at the time of Covid-19 infection can help indicate whether a person is likely to develop long-term Covid.
The study, published in the journal Lancet eBioMedicine, examined proteins in the blood of healthcare workers infected with SARS-CoV-2 and compared them to samples from uninfected healthcare workers. Protein levels in the body are usually steady. However, the researchers discovered a significant variation in the levels of several of the proteins up to six weeks after infection, suggesting that a number of critical biological processes were disrupted.
Using an artificial intelligence (AI) algorithm, they identified a “signature” in the abundance of different proteins that successfully predicted whether or not the person would go on to report persistent symptoms a year after infection.
The researchers say that if these findings are repeated in a larger, independent group of patients, a test could potentially be offered alongside a polymerase chain reaction (PCR) test that could predict people’s likelihood of developing long Covid.
The study’s lead author Dr Gaby Captur (MRC Unit for Lifelong Health and Ageing at UCL) said, “Our study shows that even mild or asymptomatic Covid-19 disrupts the profile of proteins in our blood plasma. This means that even mild Covid-19 affects normal biological processes in a dramatic way, up to at least six weeks after infection.
“Our tool predicting long Covid still needs to be validated in an independent, larger group of patients. However, using our approach, a test that predicts long Covid at the time of initial infection could be rolled out quickly and in a cost-effective way.
“The method of analysis we used is readily available in hospitals and is high-throughput, meaning it can analyse thousands of samples in an afternoon.”
Senior author Dr Wendy Heywood (UCL Great Ormond Street Institute of Child Health and Great Ormond Street Hospital) said, “If we can identify people who are likely to develop long Covid, this opens the door to trialling treatments such as anti-virals at this earlier, initial infection stage, to see if it can reduce the risk of later long Covid.”
Researchers compared blood plasma samples obtained every week for six weeks in spring 2020 from 54 healthcare workers who had PCR, or antibody-confirmed infection, to samples taken during the same period from 102 healthcare workers who were not sick.
They examined how Covid-19 altered these proteins over the course of six weeks using targeted mass spectrometry, a type of study that is particularly sensitive to small changes in the amount of proteins in blood plasma.
The researchers discovered unusually high amounts of 12 proteins out of the 91 examined in SARS-CoV-2 patients, and the degree of abnormality correlated with the severity of symptoms.
The researchers discovered that aberrant levels of 20 proteins tested at the time of the first infection predicted persisting symptoms after a year. The majority of these proteins were shown to be involved in anti-coagulant (anti-clotting) and anti-inflammatory actions.
A machine learning system based on the participants’ protein profiles was able to differentiate all 11 infected healthcare professionals who reported at least one persistent symptom after a year from infected healthcare workers who did not report persistent symptoms after a year. Another machine learning technique was employed to predict the chance of mistake, and it estimated that this strategy may have a 6% error rate.