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Scientists funded by federal government proposed a definition long covid based on symptoms identified in a large study published Thursday in the Journal of the American Medical Association.
The definition is based on 12 symptoms that most people with long Covid separate six months or more after infection from people who have not had it coronavirus.
Ever since the beginning of the pandemic, many people have suffered from myriads debilitating symptoms which persist long after they have been infected with Covid-19.
Patients have adopted the name long Covid. Scientists call this condition post-acute sequelae, or PASC.
However, there is still no systematic, universally accepted definition of long Covid for research that could serve as a basis for future tools to diagnose this condition.
“We’re really trying to come up with a concrete, replicable specific definition for long Covid,” said Dr. Leora Horwitz, study author and professor at NYU Grossman School of Medicine.
The study, funded by the National Institutes of Health, surveyed nearly 10,000 participants at 85 hospitals, health centers and community centers in 33 states.
More than 8,600 patients who had Covid were compared with more than 1,100 who did not have the virus.
The research is part of NIH’s massive $1.15 billion RECOVER research initiative, which aims to define long-term Covid, understand what causes the condition and develop treatments for it. RECOVER is short for Research on COVID to improve recovery.
Symptoms that stood out the most among participants with long Covid included loss of smell and taste, nausea after exertion, chronic cough, brain fog, thirst, palpitations, chest pain, fatigue, changes in sex drive, dizziness, gastrointestinal problems, abnormal movements and hair loss.
The researchers assigned points based on how much each symptom distinguished participants with long-term Covid from those who did not catch the virus.
A participant who has 12 or more points is predicted to have a long duration of Covid.
For example, loss of smell and taste and fatigue after exertion stood out more than other symptoms and had scores of 8 and 7 points, respectively. Palpitations and dizziness, which are characteristic of prolonged Covid, but which are also common symptoms in many other conditions, received 2 points and 1 point respectively.
Future clinical use
Horwitz, the study’s author, said the proposed definition of long Covid could help develop a method for doctors to diagnose patients.
But Horwitz said the definition presented in the study is an early working definition, still needs to be fine-tuned and is not yet ready for clinical use.
Because there is no universally accepted definition, many Covid patients have long struggled to get appropriate health care, especially early in the pandemic, as some symptoms are common to other conditions, which can make diagnosis difficult.
There are no tests that can diagnose long Covid based on blood markers. Scientists participating in the RECOVER project are trying to understand the underlying biology that causes long-lasting Covid, which could potentially lead to such tests in the future.
Horwitz said the proposed definition could help create a rubric for diagnosing long-term Covid patients in a similar way to Lupus. There is no single blood test that can diagnose lupus, so doctors also rely on a collection of common symptoms to determine whether a patient has the disease.
Horwitz said the goal is to provide researchers with a more systematic definition that can be used to answer questions about risk factors and how long Covid is after repeated infection and between different variants of the virus, among other things.
Biological samples from patients who developed prolonged Covid during the study could be used to investigate what causes the condition, potentially helping to find treatments and leading to inclusion in future clinical trials, according to the study.
Long Covid more common before omicron
The study also found that long Covid was more common among people infected before the micron variant swept the US in December 2021.
About 17% of patients who enrolled more than 30 days after infection during omicron developed long Covid. In contrast, about 35% of those infected before the omicron era developed long Covid.
But patients who were reinfected during the omicron were more likely to develop long Covid than those who reported a single infection when the variant was increasing. About 21% of patients with repeated infections who registered after 30 days experienced long-term Covid disease, compared to 16% who contracted Covid once.
People who were fully vaccinated were less likely to develop prolonged Covid, regardless of when they were infected.
About 16% of participants who were up-to-date on their injections who became infected during the omicron developed long-term Covid, compared to 22% of those who did not receive the injection. Before omicron, 31% of people who had updated their vaccinations and who became infected developed prolonged Covid, compared to 37% of people who were not vaccinated.