Defining Long COVID

Much has been written about long COVID, often with variable and conflicting definitions of the syndrome. This can result in a muddy mess when it comes to understanding it.

In this blog series, I will be writing about long COVID: what it can teach us about how medicine treats its patients, major themes from my work with long COVID patients in psychotherapy, reflections on emerging research findings, and more.

In order for there to be clarity, however, it is important to know what I am referring to when I use the term "long COVID."

The World Health Organization's Definition

In 2021, the WHO convened a panel of experts in order to establish a clinical case definition of what they termed "post-COVID-19 condition." This effort resulted in the following definition:

"Post COVID-19 condition occurs in individuals with a history of probable or confirmed SARS CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms and that last for at least 2 months and cannot be explained by an alternative diagnosis. Common symptoms include fatigue, shortness of breath, cognitive dysfunction but also others and generally have an impact on everyday functioning. Symptoms may be new onset following initial recovery from an acute COVID-19 episode or persist from the initial illness. Symptoms may also fluctuate or relapse over time."

There is a lot to unpack there, but it is important to emphasize:

• Individuals do not need to have had a confirmed SARS CoV-2 infection. This is crucial given the known inequities in access to diagnostic testing, differentials in antibody status by sex/age/hospitalization status, issues with false negatives, and the possibility that poor antibody responses may have something to do with long COVID pathophysiology.
• Symptoms may be delayed following an initial period of recovery, usually presenting within three months. It might be tempting to attribute symptoms to another process entirely when one has "fully recovered" from COVID. However, while symptoms from an acute phase may have disappeared, we do not yet know the full picture of what happens thereafter. Evidence of a heightened risk of vascular conditions such as heart attack and stroke, even after mild cases, suggests there is some dysfunction happening behind the scenes.
• Symptoms cannot be explained by an alternative diagnosis. There is some important grey area here. Take, for example, someone with preexisting cardiovascular disease that has been well controlled. If they have a heart attack six months after a positive COVID test, is this considered "explained by an alternative diagnosis?" To what degree has a COVID-19 illness impacted their underlying cardiovascular disease? What about someone with no cardiovascular history who has a heart attack or stroke within a year after a positive COVID-19 test? Some people have isolated cases of end-organ damage from the infection itself, with evidence of cardiac, renal, and pulmonary disease. Others have multiple symptoms which cannot be pinpointed to specific organ dysfunction.

Other Definitions

The CDC defines "long COVID or post-COVID conditions" as:

"A wide range of new, returning, or ongoing health problems that people experience after being infected with the virus that causes COVID-19 ... at least four weeks after infection is the start of when post-COVID conditions could first be identified ... There is no test to diagnose post-COVID conditions, and people may have a wide variety of symptoms that could come from other health problems ... Your healthcare provider considers a diagnosis of post-COVID conditions based on your health history, including if you had a diagnosis of COVID-19 either by a positive test or by symptoms or exposure, as well as doing a health examination."

As part of their Recover initiative for studying long COVID, the NIH coined the term PASC as an umbrella term referring to sequelae of COVID-19 following the acute course. The issue with this term is that it assumes clearly defined boundaries between acute and chronic courses without providing a definition or timeline.

In addition, there exist several other definitions in other countries/regions that were created by local health organizations.

Long COVID: The Patient-Coined Term

Starting in the early days of the pandemic, patients galvanized through international networks to coalesce around their shared experiences of a "long" disease course that strayed from what was being described as the norm. This working definition of long COVID was described by Munblit et al as "signs, symptoms, and sequelae that continue or develop after SARS-CoV-2 infection for any period of time; are generally multisystemic; might present with a relapsing-remitting pattern and a progression or worsening over time, with the possibility of severe and life-threatening events even months or years after infection."

It tends not to include those with an isolated condition, such as those with asymptomatic post-COVID kidney dysfunction, and usually includes those with multiple symptoms in different organ systems, many of which do not correlate to abnormalities on basic lab tests. It is also crucial to distinguish between those who experienced severe illness with intubation +/- prolonged hospitalization from those who experienced mild or moderate outpatient courses of illness, as the long-term issues both groups face may be quite different.

Now that the definition issue has been addressed, "long COVID," as coined by patients, is the definition that I will be working with in future posts. I invite you to watch this space for more long covid lessons.