SARS-CoV-2 Viral Load Predicts Need for Ventilator, Death Risk

By Reuters Staff

November 03, 2020

(Reuters) - When COVID-19 patients are admitted to the hospital with pneumonia, their risk of intubation or death can be estimated based on their viral load, a new study suggests.

"This risk can be predicted regardless of how sick they are when they are admitted, what other comorbidities they may have, their age or how many days they had symptoms," coauthor Dr. Ioannis Zacharioudakis of NYU School of Medicine told Reuters.

"In our study we found that in symptomatic patients with pneumonia caused by COVID-19 who are sick enough to require hospitalization, the amount of virus RNA detected on their nasopharyngeal swabs at the time of their admission can predict their risk of needing to be intubated or dying from the disease," he said.

"We estimated the amount of the virus through a value called the cycle threshold which is a number that shows how many times (cycles) the amplification process (polymerase chain reaction) had to be repeated in order to have enough viral genetic material for the test to detect it," he continued. "This number is readily available in commercial PCR assays used for COVID-19 diagnosis. Simply put, the machine has to work less if there is more virus, leading to fewer cycles being needed to reach positivity."

His team studied 314 patients, dividing them into three groups according to viral load upon hospital admission. Patients in the highest tertile had 59% higher odds of becoming critically ill or dying than patients in the lowest tertile.

The study, published in Annals of the American Thoracic Society, "justifies the practice of using the amount of virus detected as an additional factor to assess patients' risk of adverse outcomes," Zacharioudakis said. "This will have practical implications in our ability to judge which patients will benefit the most from early escalation of care, treatment with antivirals and/or inclusion in trials of new therapeutics in an era when we are experiencing a surge in cases around the world and hospitals' abilities are finite."

Further studies are needed to evaluate whether changes in viral load during the course of hospitalization with correlate with a relevant change in clinical outcomes, he said.

SOURCE: Journal of the American Thoracic Society, online October 29, 2020.