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 excess SARS-CoV-2 spike protein in plasma indicates long-lasting COVID-19. The researchers analyzed plasma samples collected from 63 people previously infected with COVID-19, 37 of whom had been diagnosed with PASC. Blood samples were collected at least 2 times no more than 12 months after a positive COVID-19 RT-PCR or antibody test. As a control, blood samples were also collected from 26 people who contracted COVID-19 but had a full recovery, without a diagnosis of PASC. The researchers used highly sensitive molecular array tests to measure the concentration of COVID-19 antigens. They detected either the S1 subunit of the spike, the full-length spike, or the nucleocapsid (N) in 65% of plasma from patients with PASC. Of the 3 antigens measured, spike was detected most frequently, in 60% of patients. Notably, no peak was detected in fully recovered patients with COVID-19. Of the 37 long-term COVID patients, 30 were women, confirming previous research findings that women are disproportionately affected by PASC. Of 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 spike antigen in the majority of PASC patients suggests that long-term COVID may be due to the active presence of a SARS-CoV-2 virus reservoir. The researchers noted that their sample size was small, but importantly, a spike was detected at various time points 2-12 months after infection with COVID-19.
