Long COVID now has a working case definition in the U.S.
Twelve key symptoms of long COVID include postexertional malaise, fatigue, brain fog, dizziness, gastrointestinal symptoms, palpitations, changes in sexual desire or capacity, loss of or change in smell or taste, thirst, chronic cough, chest pain, and abnormal movements, said Andrea Foulkes, ScD, of Massachusetts General Hospital and Harvard Medical School in Boston, and colleagues from the NIH's RECOVERopens in a new tab or window consortium.
Survey data from nearly 10,000 people were used to define the 12 signature symptoms, the researchers reported in JAMAopens in a new tab or window. The findings also included a symptom-based scoring system to help clinicians and researchers better identify long COVID and investigate treatments.
"One of the big takeaways from this study is the heterogeneity of long COVID: long COVID is not just one syndrome; it's a syndrome of syndromes," Foulkes said in a statement. "Understanding this idea is a really important step for doing more research and ultimately administering informed interventions."
"Now that we're able to identify people with long COVID, we can begin doing more in-depth studies to understand the biological mechanisms at play," she added.
Since 2020, researchers have documented a wide range of symptomsopens in a new tab or window that emerge after acute SARS-CoV-2 infection. Many studies have been limited by retrospective design, reliance on electronic health record data, or lack of a control group, which has led to disagreement about how common long COVID is, how severe certain symptoms may be, and what patterns define long COVID.
Incorrect case definitions can delay diagnoses, decrease the chance of finding underlying mechanisms, and lead to misdirected, ineffective treatments for long COVID (also known as post-acute sequelae of SARS-CoV-2 infection, or PASC), observed Robert Gross, MD, MSCE, and Vincent Lo Re III, MD, MSCE, both of the University of Pennsylvania in Philadelphia, in an accompanying editorialopens in a new tab or window.
Before developing a case definition for long COVID, it's important to "consider whether these sequelae represent a single pathophysiologic process or rather multiple different conditions triggered by antecedent SARS-CoV-2 infection," Gross and Lo Re wrote.
"In addition, it is important to know whether they are direct sequelae of infection itself or are mediated by specific organ injury and dysfunction," the editorialists continued. "For example, severe SARS-CoV-2 infection that requires intensive care unit admission can result in a well-described post-intensive care syndrome with many features that overlap with post-acute sequelae."
