Missteps in Creating a Long Haul COVID Case Definition

If difficulties occur in developing reliable case definitions, there are serious consequences for patients, as they would then be unsure whether or not they have the illness, as well as for scientists, who would then have difficulties in finding biomarkers.

This has occurred for the post-viral illness known as chronic fatigue syndrome, which most patients refer to as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). The consequences have been devastating in terms of increasing stigma for these patients with ME/CFS as when biomarkers are not reliably identified, health care workers inaccurately attributed their illness to psychiatric versus more biological causes.

Will a similar fate occur for the millions of people who have not recovered from the current COVID pandemic?

Patients previously infected with COVID-19 often have persisting and new symptoms. Many have termed the post-COVID-19 infection phenomenon as “long COVID” or “long haul COVID.” If only 10% develop long haul COVID, then of the 47 million current cases in the US, there will be over 4 million individuals affected. This will have significant consequences on our health care system.

Recently, the internationally respected World Health Organization (WHO) introduced a clinical case definition for those who have not recovered from being infected by COVID. Their criteria suggest that symptoms are usually three months from the onset of infection with a duration of at least two months. Their case definition also mentions that among the common symptoms are fatigue, shortness of breath, and cognitive dysfunction.

A clinical case definition is intended to be very broad so that it can include all those who have the disorder. This is in contrast to a research case definition, which is more restrictive in criteria to identify a more homogeneous sample.

It is unclear why three months have to elapse for a person to have the WHO diagnosis. In other words, those patients who continue having symptoms after the first few weeks of COVID infection are left without a diagnosis for several months, and these first few months might be a critical time for a diagnosis that could help patients secure treatment.

The next part of the WHO case definition is that the symptoms must last for two months. We know that sometimes symptoms are delayed with long haul COVID, so if symptoms emerged three months past infection, a patient would need to be sick again for two months before being provided a diagnosis and possible treatment. It would be simpler to just indicate the amount of time that has elapsed since being infected or becoming sick, as this would eliminate problems associated with individuals not being able to have a diagnose and treatment at the critical early times in the illness.

As stated above, a clinical case definition is by its very nature broad to include all those with an illness. It is very problematic that there are currently multiple definitions that have been proposed by different organizations. If scientists from around the world have been successful in developing vaccines, they surely must have the ability to reach a consensus on the case definition of long haul COVID. Below we provide some of the parameters that could be used to classify all patients as well as provide scientists with needed research case definition criteria for classification purposes.

At the present time, there is no differentiation of illness severity for those who have not recovered from COVID. It would have been relatively straightforward to categorize patients into those that are mildly, moderately, or severely affected. Those who are severely affected will be more symptomatic than those in the moderate category. Such a relatively simple rating scale could have been proposed to differentiate patients into meaningful categories, as there will be important functional reductions between such groups which will affect health care needs for services.

When diagnostic categories lack reliability and accuracy, the validity (i.e., usefulness) of a diagnostic category is inherently limited. Many of the symptoms, such as fatigue, are common among individuals who have never had COVID. Just indicating that a person has a symptom is insufficient for designating at what threshold the symptom needs to exist for it to be considered a problem. A very infrequent symptom might not be a problem for the person even if it is rather serious when it occurs, and a very frequent symptom might also be less impactful when the severity of it is minimal. Failing to differentiate frequency and severity with these types of symptoms makes it considerably more difficult to assess the impact of symptoms. In addition, the use of structured interview schedules increases the chance that the clinical material needed to apply to the diagnostic criteria is elicited by structuring and standardizing the questions asked by each interviewer. Thus, structured interview schedules serve to remove as much as possible the unreliability in the resulting diagnosis introduced by differences in the way clinicians elicit clinical information: reducing variance by having scientists and clinicians ask the same questions. Together, the provision of operationally explicit, objectively debatable criteria and standardized interviews will significantly improve the reliability of clinical diagnosis for long haul COVID. Today, there are dozens of COVID questionnaires being used to elicit patient information with inadequate or no psychometric properties.

Millions of individuals who have not recovered from the COVID virus are now dealing with a host of symptoms that are challenging our health care system. Many are experiencing significant problems in being recognized by health care workers as a real disorder, as for many of them, there are no biological markers of persistent illness. Just as with ME/CFS, we need to be sure that long haul COVID patients are not victimized first by the pandemic and then by the health care skepticism of their significant symptoms. We have the conceptual and theoretical grounding to develop clinical and research case definitions for those with persisting COVID symptoms. Patients must be instrumentally involved in all such efforts as failure to do so will only further delegitimize their condition.