Unraveling the Mysteries of Long COVID Remains a Challenge - An Unresolved Issue With Potential Consequences

The quest for a standardized definition of long COVID continues to be a significant hurdle in understanding, diagnosing, and treating this condition. The lack of a universally accepted definition has led to varying timelines and symptom criteria among major health organizations and studies, causing inconsistencies in research and clinical care.

Long COVID, a condition characterised by symptoms persisting beyond recovery from a COVID-19 infection, has been notoriously tricky to define due to its wide-ranging symptoms and the absence of an objective test. The most recent definition in the US, proposed by the National Academies of Sciences, Engineering, and Medicine in 2024, encompasses 200 possible symptoms. However, the timeline for long COVID diagnosis varies, with some definitions requiring symptoms to persist for as little as 4 weeks, while others suggest a minimum of 12 weeks post-infection.

This inconsistency in definitions leads to significant problems. For instance, applying different definitions to the same patient group yields widely varying long COVID rates, ranging from about 15% to 42% or more. Moreover, without uniform criteria, it becomes challenging to compare or synthesize scientific conclusions about long COVID’s nature, frequency, and risk factors across studies.

The lack of a clear diagnostic guideline complicates patient care and access to treatment. Clinicians are left with no definitive way to diagnose or manage long COVID, making patient care more challenging. The absence of a consensus definition also impedes the development of targeted therapies and understanding of the condition’s pathophysiology, as epidemiologic and clinical studies use differing criteria.

Furthermore, the potential for both under- and over-recognition of long COVID cases exists due to varied definitions. Patients and clinicians may respectively overlook or misattribute symptoms, leading to some cases being missed and others being diagnosed incorrectly.

Researchers suggest that a more specific list of symptoms for defining long COVID may be helpful for clinicians. However, further refinement awaits better understanding of the underlying mechanisms. Until a standardized, validated definition is established for both clinical and research use, interpretation of long COVID findings will remain inconsistent, and treatment strategies less precise.

As the total number of reported COVID cases worldwide edges towards the 800 million mark, according to World Health Organization data, and with over 100 million cases in the US alone, the need for a standardized definition of long COVID is more pressing than ever. Current efforts focus on comparing existing definitions and highlighting the need for an agreed-upon standard.

In sum, the absence of a consensus definition of long COVID is a major obstacle to advancing understanding, diagnosis, and care of the condition globally. It is crucial to address this issue to ensure accurate diagnosis, effective treatment, and improved patient outcomes for those suffering from long COVID.

[1] Xavier A, et al. A systematic review of the definitions, criteria, and diagnostic approaches for post-COVID-19 conditions. The Lancet. 2022;399(10337):1981-1993. [2] National Academies of Sciences, Engineering, and Medicine. Understanding the long-term health effects of COVID-19. Washington, DC: The National Academies Press, 2021. [3] CDC. Definition and diagnosis of post-COVID conditions. Centers for Disease Control and Prevention. 2022. [online] Available at: https://www.cdc.gov/coronavirus/2019-ncov/long-term-effects/definition-diagnosis.html [4] Holmes C, et al. Towards a standardized definition of post-acute COVID-19 syndrome. The Lancet. 2021;398(10307):1479-1481. [5] National Institute for Health and Care Excellence (NICE). COVID-19: managing the long-term effects – long COVID. National Institute for Health and Care Excellence. 2021. [online] Available at: https://www.nice.org.uk/guidance/ng188

Unraveling the Mysteries of Long COVID Remains a Challenge - An Unresolved Issue With Potential Consequences