New Tests May Finally Diagnose Long COVID

Medscape | By Sara Novak

One of the biggest challenges facing clinicians who treat long COVID is a lack of consensus when it comes to recognizing and diagnosing the condition. But a new study suggests testing for certain biomarkers may identify long COVID with accuracy approaching 80%. 

Effective diagnostic testing would be a game-changer in the long COVID fight, for it’s not just the fatigue, brain fog, heart palpitations, and other persistent symptoms that affect patients. Two out of three people with long COVID also suffer mental health challenges like depression and anxiety. Some patients say their symptoms are not taken seriously by their doctors. And as many as 12% of long COVID patients are unemployed because of the severity of their illness and their employers may be skeptical of their condition.

Quick, accurate diagnosis would eliminate all that. Now a new preprint study suggests that the elevation of certain immune system proteins are a commonality in long COVID patients and identifying them may be an accurate way to diagnose the condition.

Researchers at Cardiff University School of Medicine in Cardiff, Wales, United Kingdom, tracked 166 patients, 79 of whom had been diagnosed with long COVID and 87 who had not. All participants had recovered from a severe bout of acute COVID-19.

In an analysis of the blood plasma of the study participants, researchers found elevated levels of certain components. Four proteins in particular — Ba, iC3b, C5a, and TCC — predicted the presence of long COVID with 78.5% accuracy.

"I was gobsmacked by the results. We’re seeing a massive dysregulation in those four biomarkers," says study author Wioleta Zelek, PhD, a research fellow at Cardiff University. "It’s a combination that we showed was predictive of long COVID." 

The study revealed that long COVID was associated with inflammation of the immune system causing these complement proteins to remain dysregulated. Proteins like C3, C4, and C5 are important parts of the immune system because they recruit phagocytes, cells that attack and engulf bacteria and viruses at the site of infection to destroy pathogens like SARS-coV-2. 

In the case of long COVID, these proteins remain chronically elevated. While the symptoms of long COVID have seemed largely unrelated to one another, researchers point to elevated inflammation as a connecting factor that causes various systems in the body to go haywire.

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