New Study Reveals Varied Definitions of Long COVID Create Confusion

A recent study has highlighted significant inconsistencies in the definitions of long COVID, complicating diagnosis and treatment for patients worldwide. Researchers reported their findings on March 15, 2024, in the journal JAMA Network Open, emphasizing the urgent need for a standardized definition of this condition.

The research indicates that the definition of long COVID varies considerably among medical professionals, leading to discrepancies in identifying affected individuals. This inconsistency poses challenges for both diagnosis and subsequent treatment options for millions suffering from lingering symptoms following a COVID-19 infection. Lead researcher Lauren Wisk, an assistant professor at UCLA’s David Geffen School of Medicine, stated, “The findings highlight the need for a standard definition for long COVID.”

Multiple organizations, including the National Academies of Sciences, Engineering, and Medicine, have proposed their own definitions of long COVID, but none have gained universal acceptance. The definitions present various flaws, with the National Academies’ definition, released in 2024, being particularly broad. Critics note that it does not require laboratory confirmation of a prior COVID-19 infection, raising questions about its validity.

To explore these discrepancies, researchers analyzed five existing definitions of long COVID applied to over 4,500 COVID patients tracked as part of an ongoing research initiative. These studies were conducted in the United States, United Kingdom, Netherlands, Sweden, and Puerto Rico. The definitions varied in terms of symptom duration, with some requiring symptoms to persist for as little as four weeks, while others extended to six months. Additionally, the number of symptoms considered ranged from as few as nine to as many as 44.

The findings revealed that the percentage of patients identified as having long COVID fluctuated between 15% and 42%, depending on the definition applied. This wide range can result in missed diagnoses for legitimate cases of long COVID, as well as misdiagnoses for individuals who do not actually have the condition. Senior researcher Dr. Joann Elmore emphasized the significance of a unified definition, stating, “Without a shared definition, we risk mislabeling patients and misguiding care. This is more than an academic debate — it affects real people.”

The study underscores that these variations in definitions also hinder the medical field’s ability to understand long COVID comprehensively. Wisk pointed out, “If every study on long COVID uses a different definition for identifying who has it, the scientific conclusions become harder to compare across studies and may lead to delays in our understanding of it.”

In the absence of an objective measure, such as a blood test, or a uniform standard for diagnosing long COVID, researchers and healthcare practitioners must navigate which definitions best suit their inquiries and be transparent about the limitations of their choices.

For those seeking further information, the U.S. Centers for Disease Control and Prevention provides additional resources on long COVID. The ongoing research and discussions surrounding this condition highlight the pressing need for clarity in definitions, ultimately aiming to improve patient care and outcomes in this evolving area of medicine.