Long Covid continues to evade a clear diagnostic test, researchers reported in a study published Monday in the Annals of Internal Medicine.
The findings are part of the National Institute of Health’s RECOVER Initiative, a billion-dollar-plus effort launched in 2021 to research causes and treatments for the estimated 17 million Americans with long Covid.
Monday’s study used data from more than 10,000 patients at 83 clinical sites around the country. The researchers looked at a number of lab results from the patients, including routine blood counts; kidney and liver tests results; and markers of inflammation in the body. They found no differences between those with long Covid and those without the condition.
Dr. Kristine Erlandson, the lead author of the study and an infectious disease physician at the University of Colorado Anschutz Medical Campus, said she was disappointed they weren’t able to find a test that could clue doctors into long Covid.
“I think it is consistent with what we’ve learned more recently,” Erlandson said. “It’s really a symptom-driven condition and there isn’t a specific laboratory value that points us towards that definition or diagnosing someone with long Covid.”
In an accompanying editorial, doctors at Johns Hopkins University School of Medicine wrote, “Clinicians are left to continue doing what we have done in the past: order tests to rule out alternative explanations rather than to diagnose long COVID.”
Patients in the study were determined to have long Covid based on a scoring system of 12 symptoms including brain fog, dizziness and palpitations, among others. Different symptoms were assigned different scores, and a long Covid diagnosis was met if the score reached a level of 12.
There was no time cutoff for symptoms and a positive Covid test was not required for diagnosis.
Dr. Marc Sala, a pulmonologist and co-director of the Comprehensive Covid Center at Northwestern Medicine, said the study was well done but noted that the results might be frustrating to the millions out there still suffering from the illness.
“I think one of the criticisms that can be leveled against the study is that a lot of these labs that they sent are the same things that you get with your primary care doctor,” Sala said. “A lot of these tests weren’t exactly nuanced to looking for a novel reason for long Covid.”
Sala said that while routine blood tests are often normal with his long Covid patients, more specialized testing — such as blood tests while a patient is exercising, or a CT scan after Covid pneumonia — turns up abnormal. He said patients, particularly those who are otherwise healthy and come in with an extraordinary amount of shortness of breath and fatigue, would need much more testing beyond what was done in the paper.
Erlandson, the study author, said that this research is a first step and more specialized tests are being performed as part of additional research for the RECOVER Initiative.
Dr. Nisha Viswanathan, the director of the long Covid clinic at UCLA Health, was not surprised with the results based on her experience working with long Covid patients for three years.
“One of the things about long Covid that is so striking is the fact that at least our standard medical examinations have come up negative, yet our patients are struggling with ongoing symptoms,” Viswanathan said.
She said she’s hopeful that there will one day be a biomarker for long Covid, pointing to recent preprint, or non-peer-reviewed study, from Yale School of Medicine showing high levels of autoantibodies, or antibodies that attack the body instead of intruders, as a potential clue.
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