The has just proposed a new case definition for long COVID. The criteria specify that the condition "is present for at least 3 months as a continuous, relapsing and remitting, or progressive disease state" and the condition can be defined by "single or multiple symptoms" that "can range from mild to severe." We are also informed that there are "more than 200" possible symptoms. Finally, although "some individuals with long COVID are severely affected," there are no specific limitations in functioning.
In practical terms, this ensures that the criteria have good sensitivity, meaning that everyone who has long COVID will probably be included. That's good news for making certain that struggling patients are not left behind. However, the specificity is rather poor, which translates into inaccurately diagnosing many who do not have long COVID. This has implications for medical billing, disability benefits, and social accommodations, not to mention the consequences that can come from slapping a chronic illness label on a patient.
Overly Broad Criteria
Here is the problem: a person can meet these proposed long COVID criteria by merely having one symptom that is not a burden to the person or does not have any negative impact on the person's functioning. If a person has trivial pain in the toe for 3 months following COVID infection, with no negative consequences to the person's functioning or quality of life, that person would still be eligible for a long COVID diagnosis. The failure to list any thresholds of frequency or severity of symptoms, so that the symptoms are not trivial, has major consequences for an infection that is as widespread as COVID. The authors of this report even note, "It is reasonable to estimate that 80-to-90 percent of all adult Americans were infected at least once between 2020 and the end of 2023 (CDC, 2024b)."
Had the authors applied their criteria to a data set, such findings might have provided them with some of the implications of their recommendations. For example, I just examined a group of 100 healthy individuals who had completed a 54-item symptom questionnaire that listed . If I had instead applied a simple formula in my data set identifying individuals who had at least a minor severity of symptoms -- which is all the proposed long COVID symptom criteria would require -- then 99% of the sample would be eligible for a diagnosis.
The Implications
So, if the vast majority of citizens are eligible for a long COVID diagnosis given their prior infection, and the threshold criteria for being diagnosed is so minimal, then it is possible that the prevalence of long COVID could increase exponentially. The authors recommend their new criteria being employed throughout the U.S., including: "the federal government, state, tribal, local, and territorial health authorities; clinical societies and associations; public health practitioners; clinicians; payers; researchers; drug industry; employers; educators; international organizations; and patients." There will be a wide-ranging impact of this new case definition, because it will be used with billing codes (e.g., ICD codes) in an outpatient or inpatient setting, as well as for other purposes from school or workplace accommodations to (amid dwindling Social Security dollars).
In addition, the authors note that their recommendation may need to be "updated in no more than 3 years' time." But the last time (2015) the National Academies made a of the Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) case definition group within 5 years, it never occurred. Given this track record of failure to reconvene and reassess, will a similar fate occur with long COVID?
That 2015 National Academies report also made the unfortunate recommendation to have almost no exclusionary illnesses for ME/CFS, and as a result of this broadened criteria, prevalence rates are estimated to have . Furthermore, while the new ME/CFS case definition was designed to be used for clinical purposes, it is now used for research purposes. This can lead to inclusion of trial participants who may not actually have ME/CFS, skewing research findings. We can expect a similar pattern to occur with the newly proposed long COVID case definition.
We must learn from past experiences with other post-viral illnesses. Patients with ME/CFS have had to endure the losses of a debilitating illness and then be of healthcare workers, friends, and even family members to their disease. This is due, in part, to an empathy breakdown causing stigma. Because experiences fatigue, many feel their experience of illness is comparable to ME/CFS; so, an unwitting conscious or unconscious bias is that if they can cope with fatigue, why can't those with ME/CFS?
These attitudes trivialize the experience of ME/CFS, because garden-variety fatigue is not debilitating ME/CFS. Of note, seeking medical treatment for ME/CFS report feelings of estrangement; with ME/CFS report delegitimizing experiences by physicians; and cannot find a single knowledgeable and sympathetic physician to take care of them. We must do all we can to avoid such trauma for patients with long COVID.
Avoiding the Same Old Mistakes
There is one bright side to the report that was not afforded to patients with ME/CFS. When the 2015 National Academies report was issued, they made the unfortunate recommendation to rename ME/CFS to systemic exertional intolerance disease (SEID), a name quickly rejected by both patients and government officials. At least the authors of this new report have settled on a term, "long COVID," that has been embraced by most patient groups and researchers.
Yet, there's still a chance to make this proposed case definition narrower.
Case definitions are crucial for science, and even more critical for diseases like long COVID that lack a consistent biomarker. There is a clear benefit for a more uniform long COVID case definition, because currently physicians make this diagnosis on a case-by-case basis with a mix of definitions and their judgment. But there are potential negative consequences of an overly broad long COVID case definition.
Because a of primary care patients have unexplained symptoms, healthcare workers often do not know what is causing their symptoms or how to help them. Physicians might feel better providing a nebulous diagnosis like the proposed National Academies long COVID definition, but in the long-run, I doubt this helps patients.
is a professor of psychology and director of the Center for Community Research at DePaul University. He recently co-edited the book, . He serves as ME/CFS expert for ILLInet RECOVER.