RESEARCH TRIANGLE PARK – As the number of COVID-19 pandemic victims continues to increase as well as the number of deaths, researchers are warning that current one-time screening methods are missing many infections. Measures to fight COVID-19 therefore remain “very important.”

“One-time screening in apparently healthy people is likely to miss people who are infected. The author team are unsure whether combined screenings, repeated symptom assessment, or rapid laboratory tests are useful,” say the reseachers in a study for which a researcher at RTI International in RTP is the lead author.

These approaches could miss anywhere from 20-100% of people infected with COVID-19, RTI noted.

“As more people become infected, screening will identify more cases. However, because screening can miss people who are infected, public health measures such as face coverings, physical distancing, and quarantine for those who are apparently healthy, continue to be very important,” the study warned.

There’s another side effect, the study concludes: Screenings “could also increase the risk of identifying false positive cases, leading to unnecessary isolation.”

“Our research shows that the likelihood of missing a person who may have COVID-19 through screening is extremely high,” explained Viswanathan, a Ph.D. and an expert in systemic review methodology who is the director of the RTI-UNC Evidence-based Practice Center.

RTI image

Meera Viswanathan

To improve detection, Viswanathan cited three “key measures:”

  • Screening methods that are more sensitive and accurate
  • A robust public health infrastructure with a testing plan put into place
  • Public buy in — testing will not succeed without public acceptance

“Currently, when someone is screened negative, the assumption is that they do not have COVID-19. Because asymptomatic spread is so common, we cannot make that assumption,” Viswanathan she added. “If more accurate screening methods are developed in the future, and they are going to be used as a tool to find COVID-19 cases, they should be followed up with measures like testing and isolation for positive cases and quarantine for those suspected to be infected.”

The study, published through an alliance of scientists, health care providers and others known as Cochrane, reviewed results from 20 studies focusing on COVID-19 testing. They found the following:

  • All screening strategies (17 studies, 17,574 people), incorrectly identified:

between 20 and 100 out of 100 infected people as healthy
between 0 and 38 people out of 100 healthy people as infected

  • Asking about symptoms (13 studies, 16,762 people ), incorrectly identified:

between 40 to 100 out of 100 infected people as health
between 0 to 34 out of 100 healthy people as infected

  • Temperature measurements, asking about international travel, exposure to known infected people and exposure to known or suspected infected people (6 studies, 14,741 people), incorrectly identified

between 77 and 100 out of 100 infected people as health
between 0 and 10 out of 100 healthy people as infected

  • Asking about symptoms plus temperature measurement (2 studies, 779 people), incorrectly identified:

between 31 and 88 out of 100 infected people as health
between 0 to 10 people out of 100 healthy people as infected

However, the researchers said they had “insufficient evidence from two small studies on rapid laboratory tests and repeated symptom assessment to tell how accurate they were in identifying healthy and infected people.”