Patients with long Covid who are suffering from fatigue and shortness of breath a year after the original infection show signs of autoimmune disease, say researchers.
Analysis of blood samples from 106 patients with ongoing symptoms at three, six and 12 months after Covid infection showed specific antibodies that have been linked with autoimmune diseases.
Reporting in the European Respiratory Journal, researchers found nearly 80% of the long Covid patients had two or more ‘autoantibodies’ in their blood three months and six months after the infection. By 12 months this had fallen to 41%.
By contrast blood samples from healthy volunteers showed no sign of the autoantibodies.
Analysis of samples from controls who had experienced a non-Covid respiratory infection, found levels of the autoantibodies were comparatively low.
Two specific autoantibodies (called U1snRNP and SSb-La), persisted in around 30% of Covid patients a year after infection as did pro-inflammatory cytokines such as TNF-alpha and this tended to be among those patients who were also still suffering with fatigue and shortness of breath, the Canadian researchers said.
The finding offers clues about the nature of long Covid that could potentially lead to improvements in diagnosing and treating the condition, they concluded.
Most patients were still taking part in the study at six months but by one year only 57 came back, which may be because they had recovered, they noted.
Study leader Dr Manali Mukherjee from McMaster University in Ontario said: ‘Although long Covid is now recognised by bodies like the World Health Organization, we still know very little about why it develops or how we can help patients.
As a respiratory researcher who has studied the immune system it was her own experience with long Covid symptoms that prompted the research, she added.
‘For the majority the patients in our study, even if they had autoantibodies soon after their infection, this resolved after 12 months.
‘However, in some patients, autoantibodies persist, and these patients are more likely to continue suffering with symptoms and to need medical help.
‘These results point towards the need to test for signs of autoimmune disease in patients with symptoms of long Covid that last for a year or more.’
The team are continuing to follow the patients over two years.
In an assessment of the impact of the Omicron variant on the NHS, the DHSC has estimated there are now two million people who have self-reported long-Covid.
The prevalence has increased due to the high numbers of people infected since the emergence of Omicron, the analysis said, as there is some evidence vaccination reduces the risk of developing long Covid symptoms.
Dr Eva Polverino, head of the European Respiratory Society’s Respiratory Infections Assembly, said there was a lack of evidence on why some people develop long Covid and how we can help patients recover.
‘We know that certain infections can, in some cases, trigger longer-term autoimmune diseases such as rheumatoid arthritis.
‘This study adds to growing evidence that similar processes may be involved in long Covid.’