New research identifies immune system activity as likely cause of long Covid

New research has revealed changes in our blood proteins caused by our body’s own immune defenses are the likely cause of long Covid. A leading medical expert says we can now develop simple blood tests to identify people with the debilitating condition.

Almost four years after it was first reported, the likely cause of long Covid has been identified. Pinpointing the cause of the debilitating condition could now lead to new treatments.

Long Covid is a life-changing condition that causes chronic fatigue, breathlessness, ‘brain fog’, anxiety and stress, leading to significant impact on our daily life. Around 1.9 million Brits suffer from it and around 1 in 20 people who contract Covid-19 go on to develop long Covid. Concerningly, 41% of long Covid patients report serious health issues lasting at least two years. There are currently no diagnostic tests and few therapeutic solutions for affected patients.

It has long been hypothesized that immune dysfunction underlines long Covid, and now research has determined it is due to increased activation of the “complement system”. The complement system is major part of the body’s immune defenses that normally helps to clear infections and clean up damaged cells. Ironically, in long Covid cases, it is causing the problems."

Dr Avinash Hari Narayanan (MBChB), Clinical Lead at London Medical Laboratory, (LML)

‘A new report, published in Science last week, found patients experiencing long Covid symptoms exhibited changes to their blood serum proteins. These changes indicated that the complement system was abnormally activated, altering blood coagulation and causing tissue injury. Medical professionals call this “thrombo-inflammation”.

‘Together with changes at a cellular level to blood platelets, these results show potential new biomarkers for diagnosis of long Covid and will inform research for future treatments.

‘For many months after the first Covid patients began to report debilitating, persistent symptoms, long Covid was regarded with skepticism by some employers and even health professionals. The crux of the problem was its distinct pattern of presentation, with no identifiable cause.

‘Now the cause of the condition has potentially been recognized after pioneering research by scientists from the UK, Switzerland, the USA and Sweden. The team followed 39 healthy controls and 113 Covid-19 patients for up to a year after initial confirmation of acute Covid infection. At six months, 40 patients had developed long Covid symptoms.

‘They found several differences in the blood of people with long Covid compared to those without it, including an imbalance in proteins involved in blood clotting and inflammation. This was linked to increased activation of the complement system.

‘People with long Covid symptoms lasting six months or more had reduced levels of some proteins involved in the complement system and elevated levels of others, compared with fully recovered or healthy participants. Interestingly, those patients who initially had long Covid but whose symptoms ended within six months found their complement systems returned to normal.

‘In addition to offering a basis for easily diagnosing the condition, the study will help clinical researchers find ways to modulate and regulate the complement systems of patients suffering from long Covid, potentially offering an opportunity to understand and manage the condition.

‘Already, “off-the-shelf” blood tests can easily identify inflammation in the body and that can be used to indicate the likelihood of long Covid. A heart health profile test measures “C-Reactive protein” (CRP) that indicates inflammatory burden and cardiovascular risk. It is also an excellent indicator of high cholesterol and other issues.

‘London Medical Laboratory’s Heart Health Profile test is already widely used to identify a number of conditions. The simple, finger-prick blood test indicates risks to heart health and includes a full cholesterol profile, as well as testing for inflammation. It also tests for diabetes, showing how well the body is controlling blood sugar.

‘The Heart Health Profile test can be taken at home through the post, or at one of the many drop-in clinics that offer these tests across London and nationwide in over 120 selected pharmacies and health stores.