Long COVID cannot be reliably diagnosed in routine lab tests, according to international researchers.
A study of over 10,000 adult patients found that more unique biomarkers are needed to accurately identify and treat the condition that almost 1 in 5 Australians suffer from.
Researchers from America's National Institute of Health (NIH) performed 25 routine lab tests on patients enrolled in the RECOVER (Researching COVID to Enhance Recovery) trial to investigate whether patients with a prior COVID-19 infection exhibited similar physical abnormalities compared to those without one.
According to researchers, lab tests revealed markedly few differences in biomarkers between the two demographics.
Biomarkers are naturally occurring molecules, genes, or characteristics that are signs of a normal or abnormal condition, disease, or process.
Those previously infected exhibited signs of early kidney disease associated with heart disease, but those symptoms were only observed in a minority of people.
Similarly, a difference in test results suggesting heightened risk of diabetes in previously-infected patients disappeared when those without pre-existing diabetes were eliminated.
Long COVID, or SARS-CoV-2, describes a cluster of overlapping medical symptoms that persist for weeks or months after a COVID-19 infection, including tiredness and fatigue, 'brain fog', sleep problems, coughing, and shortness of breath.
No validated clinical biomarkers for long COVID currently exist, meaning diagnosis requires gathering a patient's detailed medical history, physical exams, and using laboratory testing to rule out other conditions.
The study's participants completed a baseline set of surveys, a physical examination, and 25 standard laboratory blood and urine tests. They were then tested over two years with regular surveys and lab tests.
"Long COVID symptoms can prevent someone from returning to work or school, and may even make everyday tasks a burden, so the ability for rapid diagnosis is key," said David Groff, director for the Division of Cardiovascular Sciences and the NIH's National Heart, Lung, and Blood Institute.
"Our challenge is to discover biomarkers that can help us quickly and accurately diagnose long COVID to ensure people struggling with this disease receive the most appropriate care as soon as possible."