New research definition for Long COVID

The RECOVER Initiative has revised the research definition for Long COVID. This definition differs from a classic case definition, as it was developed for research and not for diagnosis by doctors. A standardised definition of Long COVID in research is important, among other things, so such studies can be conducted in a more uniform manner and be better compared with each other. 

The revised research definition includes data from a total of 13,647 adults with and without previous infection with the SARS-CoV-2 coronavirus. The so-called ‘Long COVID Research Index’ of 2024 translates the existing symptoms of the individuals into a score. On the basis of this value, a probable Long COVID disease and a possible Long COVID disease can then be differentiated. 

Based on the data, the researchers were able to differentiate between 5 different forms (‘subtypes’) of Long COVID, each with its own characteristic symptoms. In subtype 1, the focus is on changes in odour or taste. Subtype 2 is characterised by a chronic cough. Subtype 3 describes reduced mental performance (‘brain fog’) as a characteristic symptom. People with subtype 4 suffer from a clearly noticeable, faster or irregular heartbeat. Subtype 5 includes people with pain after physical exertion, dizziness and gastrointestinal symptoms. Subtypes 2 to 5 also include fatigue and discomfort after exercise. Subtype 5 shows overlaps with myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS).

The application of the revised research definition in clinical studies should help to better take into account the complexity of the pattern of illness and the differences between different patient groups.