A new study found that most routine laboratory tests are not reliable for diagnosing Long COVID, also known as Post-Acute Sequelae of SARS-CoV-2 infection (PASC).
The study, published today in Annals of Internal Medicine, found no reliable biomarker among 25 routine clinical laboratory values for prior infection, PASC or specific types of PASC clusters. This suggests none of these routine labs can serve as a clinically useful biomarker of PASC.
„Our study shows patients can have severe Long COVID with normal lab results. This suggests doctors should not focus on the results of blood panels to diagnose Long COVID but should focus more on symptoms and ways to help patients get relief by treating their symptoms,“ said the study’s first author, Kristine Erlandson, MD, a professor in the Division of Infectious Diseases at the University of Colorado Anschutz Medical Campus.
Seven percents of all adults in the U.S., nearly 18 million people, currently have long COVID, according to Agency for Healthcare Research and Quality’s Medical Expenditure Panel Survey.
To investigate clinical laboratory markers of SARS-CoV-2 and PASC, the researchers examined data from nearly 10,000 adults with and without SARS-CoV-2 infection. The researchers recruited from over 80 enrolling sites across 33 U.S. states plus Washington, DC and Puerto Rico, making it one of the largest and most diverse studies of its kind.
The study compared results in several ways: between participants with and without prior SARS-CoV-2 infection at six months after infection, between participants with and without PASC and between participants with each of four most common PASC symptom phenotypes and those unlikely to have PASC.
They found participants with prior SARS-CoV-2 infection showed modest increases in HbA1c (a marker of long-term blood sugar levels) and urinary albumin-to-creatinine ratio (uACR), along with small decreases in platelet counts.
“While these differences are statistically significant, these associations are generally small and not reliable enough to serve as diagnostic biomarkers for PASC,” Erlandson says.
The researchers suggest this data shows the complexity of PASC as a condition that may involve multiple physiological pathways beyond simple laboratory markers, such as those for inflammation, anemia or other markers.
https://www.acpjournals.org/doi/10.7326/M24-0737
