Four parameters are enough to predict the risk of developing persistent Covid syndrome or Long Covid. According to a study published in «Nature Communications» the key lies in an immunological signature – lower levels of certain antibodies in the blood-, which when combined with a history of asthma, age and some symptoms of Covid-19, determines the risk of Long Covid.
The acute infection that causes the SARS-CoV-2 coronavirus can affect multiple organs and even after the elimination of the infection, the symptoms can persist in the long term. About a third of infected people report symptoms lasting more than four weeks after initial infection.
Persistent Covid, a little-known situation, for which there is no definition, standard diagnosis or treatment, has baffled doctors and researchers around the world since the pandemic began.
The exact number of patients with persistent Covid is unclear, although it is estimated that a third of Covid patients overall may experience symptoms for at least a month.
Any initial information about which patients may end up becoming so-called long-term patients will be very helpful.
already described more than 200 different symptoms associated with persistent Covidand. They are grouped into three major phenotypes: respiratory, fatigue and cognitive, but, the heterogeneity, combinations of symptoms and inter-individual variability stand out, they had not been seen before in any viral or bacterial infection.
If confirmed by larger studies, this research could help scientists develop a test to predict who may continue to experience symptoms weeks, months, and even years after infection.
Not surprisingly, it is estimated that 16% of people who overcome acute Covid-19 infection develop Long Covid. Thus, taking into account that there are more than 265 million people in the world, and in Spain more than 5 million have been infected by the coronavirus, in Spain for example there could be up to 800,000 patients, that will require attention, follow-up by multiple specialists and many diagnostic tests, which will once again collapse hospital outpatient services and probably also Primary Care services, both of which are already very damaged and exhausted.
The team of Onur Boyman, author of the new study and researcher at the department of immunology at the University Hospital of Zurich (Switzerland), analyzed a cohort of 215 people; 175 tested positive for SARS-CoV-2 and 40 were healthy controls. Of the 175 people who tested positive, 134 were followed up to a year after initial infection.
The authors identified 89 mild cases and 45 severe casesis. 53.9% of mild cases and 82.2% of severe cases of Covid-19 developed persistent Covid, defined by the persistence of one or more symptoms related to Covid-19 for more than four weeks after onset of the symptoms.
The authors analyzed antibody levels and other clinical parameters and identified a signature based on lower levels of total immunoglobulin M (IgM) and immunoglobulin G3 (IgG3), older age, history of asthma, and five symptoms (fever, fatigue, cough, shortness of breath, and gastrointestinal symptoms) reported during primary infection that could be used to predict the risk of developing Long Covid.
The results confirmed this in an additional cohort of 395 people with Covid-19.
“We want to be able to recognize and identify, as soon as possible, who is at risk of developing persistent Covid,” says Onur Boyman.
Boyman’s research began in early 2020, during the first wave of the pandemic. His team followed patients through the acute phase of infection, then for six months, and then for a year as the phenomenon of persistent Covid became apparent.
Comparing more than 500 Covid patients, some of whom suffered from Covid for a long time and others whose symptoms resolved, several key differences emerged.
The most obvious was how the immune systems of patients who developed Covid for a long time initially reacted al virus.
Such patients in Boyman’s study showed marked decreases in levels of two immunoglobulins, IgM and IgG3, which are antibodies produced by the immune system to fight infection.
Those antibody levels, when combined with other factors, such as middle age and a history of asthma, were 75 percent effective in predicting Long Covid, Boyman said.
Because the researchers have known which patients suffered from Covid for a long time, more research is needed to determine whether the criteria would be as accurate from the onset of the disease.
The investigation did not include the Omicron variant. Study patients were infected between April 2020 and August 2021, before this variant was established
So it’s not clear whether the findings would apply to those who can develop Covid long after infection. Omicron.
In addition, the study did not take into account the vaccination status of the participants. Many of the long-term Covid patients fell ill in early 2020, before vaccines were available.