Boston—
Screening asymptomatic people for COVID-19 with low-expense testing is cost-effective and decreases infections and death.

A report in Clinical Infectious Diseases points out that, even when the pandemic is slowing down, low-cost, recurring screening of those showing no symptoms at a cost of about $3 or less per test every 2 weeks would be worth it. 

In addition, when the pandemic is surging, Massachusetts General Hospital–led researchers advise that screening can be cost-effective when done more frequently, even if testing costs rise.

The article explains that COVID-19 testing refers generally to assays of people with symptoms of the illness, while screening refers to testing of individuals who do not have symptoms of the infection. 

“Massachusetts experienced a major COVID-19 outbreak beginning in March 2020, and while the outbreak is now under reasonably good control, questions remain about how to optimally deploy COVID testing, both in our current situation and in other settings—and communities—where new infections continue to rise,” explained lead researcher Anne Neilan, MD, MPH, investigator in the MGH Divisions of General Pediatrics and Infectious Diseases and the Medical Practice Evaluation Center.  “While some have argued testing must be highly sensitive to be of value, others suggest that sensitivity can be sacrificed if tests are rapid, low-cost, frequent and widely available.”

A dynamic transmission model developed by members of the research team—the “CEACOV model”—was used to analyze the outcomes anticipated from several different strategies for COVID-19 testing and screening for the entire population of Massachusetts. The study assumed use of the laboratory-based polymerase chain reaction (PCR) tests, which involves a sample, usually nasal swab or saliva, taken from the nose or mouth; the test is then sent to a laboratory that screens for the virus causing COVID-19.

Researchers note that their model-based analysis revealed that repeated screening of the entire population would lead to the most desirable clinical outcomes, preventing infections, hospitalizations, and deaths most effectively. 

“Based on the prices that most laboratories are now charging for the PCR test, with our current levels of new COVID-19 cases in Massachusetts, the most cost-effective strategy remains testing only people with symptoms of COVID-19. Importantly, for Massachusetts as of now, this includes testing all people with symptoms, and not only people whose symptoms are severe,” points out study cosenior author Andrea Ciaranello, MD, MPH, investigator in the Division of Infectious Diseases at MGH. “However, in locations where cases are rising, regular screening of the entire population, while expensive, will actually be of very good value. This is true even at current testing costs around $50 and will be truer if test costs can be brought down substantially.”

Ways to bring tests costs down include using less expensive reagents, pooling of specimens in the lab or carefully allocating unused testing capacity across cities or regions,” Dr. Ciaranello said.

Dr. Neilan added, “When the pandemic is slowing, if testing costs can come down to $5 or less, repeat screening of people without COVID symptoms would decrease infections and deaths, and be cost-effective.”

The study compared four testing strategies: 
1. Hospitalized: PCR testing only patients with severe/critical symptoms warranting hospitalization; 
2. Symptomatic: PCR for any COVID-19-consistent symptoms, with self-isolation if positive; 
3. Symptomatic plus asymptomatic-once: Symptomatic and one-time PCR for the entire population; and, 
4. Symptomatic plus asymptomatic-monthly: Symptomatic with monthly re-testing for the entire population. 

Researchers considered effective reproduction numbers (Re, 0.9-2.0) at which policy conclusions would change. Results indicate that, at Re 0.9, symptomatic plus asymptomatic-monthly screening versus just testing hospitalized patients resulted in a 64% reduction in infections and a 46% reduction in deaths but required greater than 66-fold more tests/day with five-fold higher costs. Symptomatic plus symptomatic-monthly had an incremental cost-effectives ration less than $100,000 per quality of life year only when Re  was greater than 1.6; test cost was $3 or less and every 14-day testing was cost-effective at all Re examined.

“Testing people with any COVID-19-consistent symptoms would be cost-saving compared to testing only those whose symptoms warrant hospital care. Expanding PCR testing to asymptomatic people would decrease infections, deaths, and hospitalizations. Despite modest sensitivity, low-cost, repeat screening of the entire population could be cost-effective in all epidemic settings.

The researchers did not evaluate the possible use of less-sensitive but less-expensive tests, such as rapid tests used on-site at healthcare facilities, schools, or workplaces.

Dr. Ciaranello emphasized that repeat screening is essential, noting, “Screening a group of people just one time, while an interesting snapshot, is an approach that will miss many people who will become able to infect others in the future. Because of this, we also found that screening just once was a less efficient use of healthcare resources under most circumstance than strategies using repeat testing.”

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