There are many studies investigating why some people experience “long COVID” and others do not, but diagnosing and treating post-acute complications of COVID-19 (PASC) continues to be a challenge for healthcare providers.
A study published in medRxiv sought to identify PASC biomarkers to improve long-term diagnosis of COVID. The team of researchers from Brigham and Women’s Hospital and Massachusetts General Hospital found that an excess of spike protein of SARS-CoV-2 in plasma indicates a long COVID.
The researchers analyzed plasma samples collected from 63 individuals previously infected with COVID-19, 37 of whom were diagnosed with PASC. Blood samples were collected at least 2 times no more than 12 months after a positive RT-PCR for COVID-19 or antibody test. As a control, blood samples were also taken from 26 individuals who had contracted COVID-19 but had fully recovered without a diagnosis of PASC.
The researchers used ultrasensitive single molecule array assays to measure the concentration of COVID-19 antigens. They detected the S1 subunit of the spike, full-length spike, or nucleocapsid (N) in 65% of plasma from patients with PASC. Of all 3 antigens measured, a peak was most frequently detected, in 60% of patients. It should be noted that no peak could be detected in fully recovered patients with COVID-19.
Of the 37 persistent COVID patients, 30 were women, confirming previous research findings that women are disproportionately affected by PASC. Among the 26 patients not diagnosed with PASC, 10 were admitted to the intensive care unit (ICU) and 7 were intubated.
The presence of SARS-CoV-2 peak antigen in most PASC patients suggests that prolonged COVID may be due to the active presence of a SARS-CoV-2 viral reservoir. The researchers noted that their sample size was small, but it is significant that the peak was found at different time points 2-12 months after contracting COVID-19.
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