The risks of contracting long Covid may have been exaggerated because of ‘methodological flaws’ in how the long-term symptoms sometimes left after the virus are being studied, research has suggested.
The research team from the UK, Denmark and the US have concluded that “many” scientific journals end up overstating the prevalence of long Covid because of a combination of “overly broad definitions, lack of control groups, inappropriate control groups, and other methodological flaws”.
Instead, the authors argue long Covid’s symptoms are common among a range of upper respiratory viruses.
It has been estimated that more than two million people in the UK may be suffering from long Covid, with symptoms often varying widely, but including chronic fatigue, shortness of breath and ‘brain fog’.
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The research team, led by Dr Vinay Prasad , professor of epidemiology and biostatistics at the University of California in San Francisco, said the lack of definition around long Covid could end up leading to an increase in healthcare spending and more anxiety, as well as a risk of misdiagnoses and diversion of funds.
The study, published in the journal BMJ Evidence-Based Medicine, examined the definition of the condition as set out by several global health organisations, including the National Institute for Health and Care Excellence (NICE) and the World Health Organization (WHO).
“In general, in the scientific literature, imprecise definitions have resulted in more than 200 symptoms being associated with the condition termed long Covid,” the researchers said.
Studies carried out in the early stages of the pandemic were more likely to have included fewer patients, some with mild or no symptoms, which could have led to a sampling bias, they added.
“Our analysis indicates that, in addition to including appropriately matched controls, there is a need for better case definitions and more stringent (long Covid) criteria, which should include continuous symptoms after confirmed SARS-CoV-2 infection and take into consideration baseline characteristics, including physical and mental health, which may contribute to an individual’s post-Covid experience,” the team argued.
They recommended there needs to be “internationally established” diagnostic criteria for long Covid and called for future studies to avoid “umbrella terms”.
“Inappropriate definitions and flawed methods do not serve those whom medicine seeks to help. Improving standards of evidence generation is the ideal method to take long Covid seriously, improve outcomes, and avoid the risks of misdiagnosis and inappropriate treatment,” the research team argued.
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