Can Long COVID researchers learn from ME/CFS?

There is a dizzying array of case definitions for long COVID that vary in terms of the name of this condition, duration of symptoms, types of symptoms, and medical comorbidities. The field of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has encountered comparable problems when developing case definitions over the past 3 decades. In this commentary, we will show how lessons learned from ME/CFS can help identify a variety of conceptually distinct comorbid medical conditions. This is a difficult task for those overseeing the large national COVID study, RECOVER, with more than 8,500 participants currently enrolled and a goal of 40,000 participants by the end of the year.

Participants in the RECOVER study are asked hundreds of questions at each assessment over time, and a series of questions asks patients to indicate whether participants have any comorbid conditions. RECOVER investigators want to know if these comorbid conditions are due to either: 1) the SARS-CoV-2 infection itself, such as damage to the lungs or other organs as a result of respiratory distress syndrome acute, or persistent symptoms consistent with post-USI syndrome; or 2) medical conditions that may have preceded the infection such as obesity and cerebrovascular disease. Both new and existing conditions could make recovery from COVID more difficult (and these premorbid conditions can also make a person more susceptible to SARS-CoV-2 in the first place). RECOVER officials are currently debating whether to add to their list of comorbid conditions.

However, there is another question which is equally important, but which has rarely been discussed by RECOVER scientists or others. This question is critically important in classifying long-term COVID patients, as some have “explained” conditions and others have “unexplained” conditions contributing to the onset and persistence of symptoms.

From its earliest days, ME/CFS scientists have dealt with this issue of “explicable or unexplainable” comorbidities, as many ME/CFS case definitions exclude a person from having ME/CFS if they had an explainable reason – that is, a previous diagnosis. medical condition whose resolution has not been documented beyond reasonable clinical doubt and whose continued activity may account for their chronically tiring illness. In other words, if cancer was causing their fatigue and other symptoms, they would have cancer-related fatigue, but not ME/CFS, because ME/CFS is a disease that has unexplained symptoms.

Additionally, ME/CFS researchers realized that the consequences of various medical conditions could also explain fatigue. For example, if the person with cancer had surgery or radiation therapy that resulted in fatigue and other symptoms, researchers would not classify the person as having ME/CFS because the person has another explained reason for his symptoms. However, if a person with the main symptoms of ME/CFS had cancer in the past, the cancer was successfully treated, and the cancer is no longer causing the symptoms, then the person would not have a disease. exclusion and would be eligible for ME/CFS Diagnosis.

It is extremely important to identify long-lasting COVID patients who might be classified as having unexplained persistent symptoms versus those who are explained, as these two groups might need to be differentiated when analyzing long-lasting COVID data. To do this, the RECOVER trial must collect enough information to determine if any previous uncontrolled diseases are present. We can learn from ME/CFS investigators how to gather adequate information to determine whether the patient’s persistent symptoms are due to an explained or unexplained cause. At a minimum, physicians should determine whether patients have other active, untreated disease processes that account for most of the major symptoms of post-exertional malaise, sleep disturbances, and cognitive impairment.

This information on explained/unexplained symptoms would also allow RECOVER investigators to determine whether their participants meet the criteria for ME/CFS, as there is growing evidence of multiple similarities between the two conditions. However, without this diagnostic information regarding explained or unexplained symptoms, it will not be possible to differentiate people in the RECOVER trial who have from those who do not have ME/CFS.

Leonard Jason, PhD, is a professor of psychology and director of the Center for Community Research at DePaul University. He is also the chair of the Diagnostic Tests and Testing Algorithms Subcommittee of the NIH RECOVER Working Group on Commonalities with Other Post-Viral Syndromes, and is an ME/CFS Expert for ILLInet RECOVER. Ben Katz, MD, is a pediatric physician at Ann & Robert H. Lurie Children’s Hospital in Chicago, and his research interest is the pathophysiology of viral infections in immunocompromised versus normal hosts. Benjamin Natelson, MD, is a neurologist at Mount Sinai in New York. He has studied and cared for patients with ME/CFS for many years, and is now adding the care of people with long-term COVID to his practice. Hector Fabio Bonilla, MD, is a physician and infectious disease researcher at Stanford University in California, specializing in HIV/AIDS, hepatitis C, and ME/CFS. Suvetha Ravichandran is a research assistant at the DePaul Center for Community Research where she is developing a consensus statement on ME/CFS comorbid conditions.

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