Scientists Make Breakthrough Discovery to Diagnose Long COVID
COVID-19 vaccinations saved 2.5 million lives between 2020 and 2024, according to a new comparative effectiveness study. Similar to the flu, health experts say the best defense against COVID is staying up to date with the most recent vaccine. But some variants hit harder than others, especially in children, older adults, and people who are immunocompromised. Although it’s not unusual for COVID symptoms to linger for several days or even weeks following a negative test result, symptoms that persist three months or longer after onset are an indicator of long COVID.
The chronic condition can feel “similar to autoimmune, lung, heart, neurological or psychological disorders. Some symptoms are mild and others are completely debilitating. They may come and go, change or get worse over time. You may feel like you never really got better from your initial bout with COVID at all,” explains Mayo Clinic.
It’s estimated that five to 10 percent of cases lead to long COVID. Moreover, most patients don’t feel “back to normal” for 12 to 18 months.
Despite the evolution of the COVID-19 vaccine, there isn’t an approved test for diagnosing long COVID.
“If a patient arrives in clinic and they relate the persistence of typical signs and symptoms of long COVID, 12 weeks or more after COVID -19 infection, I give them a presumptive diagnosis, but I don’t have any blood tests or biomarkers to confirm this diagnosis,” William Stringer, MD, a Lundquist Institute investigator, said in a news release.
However, Stringer and a team of scientists believe they’re on the precipice of identifying a potential long COVID biomarker. If corroborated by other research centers, the biomarker would be the first “quantifiable indicator” of its kind.
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The study, which appears in the journal Infection, was led by researchers from City of Hope’s Translational Genomics Research Institute (TGen) and the Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center.
Specifically, they were looking for traces of SARS-CoV-2 protein fragments in extracellular vesicles (EVs). These proteins don’t naturally exist in healthy human cells, leading scientists to hypothesize that their presence could be a clear biomarker for long COVID.
“Emerging evidence suggests that SARS-CoV-2 RNA and viral antigens can persist in diverse tissues (lung, brain, muscles, lymph nodes, and plasma) for months to years after acute infection, and may be pathogenic for common long COVID symptoms,” wrote the authors.
They further explained, “EVs—nanosized vesicles which facilitate intracellular communication of bioactive molecules such as proteins, lipids, nucleic acids, and metabolites—have been found to harbor other viral RNA and proteins, and may potentiate viral replication, immune activation and inflammation.”
For the study, researchers analyzed 56 blood samples from 14 individuals who had COVID within the past two years and/or people experiencing long COVID symptoms, such as fatigue, shortness of breath, and lack of energy.
Their analysis detected 65 distinct SARS-CoV-2 protein fragments within the EVs.
“Sequence analysis confirmed that these peptides were specific to SARS-CoV-2 and did not overlap with human proteins. Importantly, each subject exhibited one or more SARS-CoV-2 peptides in their EV cargo, suggesting the persistence of viral components over time,” wrote the authors.
These findings fuel a growing abundance of research that suggests COVID variants can linger and fester in tissues, plasma, and muscles long after symptoms first manifest. A biomarker of this stature could accelerate diagnoses and help patients get treatment fast.
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But while promising, the authors said there’s “still a lot to unpack.”
“We haven’t run [our tests] on people without long COVID symptoms who are currently, or who were, infected with COVID,” said Stringer. “This raises the question: is this just continuing to take out the trash from the COVID infected cell or is this really ongoing replication someplace? I think that’s the mechanistic issue that needs to be resolved in future studies.”