Many who get sick with Covid-19 end up with long term symptoms, known loosely as Long Covid. On 25 January 2022, researchers in Switzerland published research results that help to predict which Covid-19 patients are likely to develop Long Covid.
The researchers uncovered a signature immune response to the SARS-CoV-2 virus that is associated with prolonged Covid-19 symptoms. The study, which involved 215 individuals, found that those with Long Covid generally had lower levels of IgM and IgG3 antibodies. IgG3 is a specific IgG antibody produced in large numbers in response to SARS-CoV-2. By contrast, patients with both high IgM and high IgG3 were less likely to develop Long Covid.
Interestingly, individuals with a history of asthma, both those with Covid-19 and those without the illness, had lower levels of IgG3 antibodies.
In the Swiss study around 82% of severe cases and 54% of mild cases went on to develop Long Covid. In general, around one third of Covid-19 patients suffer from Long Covid with a range of 10% to 60% depending on the patients included in the study and the definition of Long Covid. Given these large numbers, understanding which patients might go on to develop Long Covid could be of significant help to doctors and patients.
Overall, the Swiss study found that Long Covid correlates with IgG3 antibody levels, patient age, history of asthma and certain symptoms in the initial phase of the illness. Based on these results, the team came up with a score based on these factors and the results of an Ig antibody test. The scoring system can be relatively easily used to predict to a high level of probability (74 AUC) whether a patient will develop Long Covid.
Research publication (in English)