JACKSON, Wyo. — In response to an influx of community questions about COVID-19 testing in Teton County, St. John’s Health and the Teton County Health Department published a letter yesterday offering more detail on each type of test.
First, there are two types of tests: active disease testing and antibody testing. “These two types of tests, ideally, may be used together to develop an overall picture of COVID-19 in our community,” the letter says. But they have very different jobs.
Active disease testing, or real-time PCR testing, is used to diagnose a person with COVID-19. It is necessary to provide real-time data on infected persons and determine who needs to be isolated or quarantine. PCR test results will come back negative if a person does not have COVID-19 at the time the test was taken, even if they have previously had it. PCR tests are what health officials are using to keep track of case counts and monitor the spread of COVID-19 in real-time.
Antibody testing, meanwhile, determines if a person has developed antibodies to COVID-19 through exposure to the virus. Importantly, it does not tell a person if they are currently infected. Antibodies form in response to COVID-19 exposure, but there is a delay between infection and antibody formation. An antibody test tests an individual’s serum, blood, plasma, or finger prick sample for the presence of IgM or IgG.
“A positive test result would indicate that a person has been exposed to COVID-19 and has developed an immune response,” the letter says. “It is important to note that current antibody testing may not be a reliable way to identify persons who are currently infected with COVID-19.”
St. John’s made the decision last week to postpone antibody testing until more is known and more FDA options are available. Currently, there is only one FDA-approved test on the market. Tests are not known to confirm immunity, measure the strength of one’s immunity, or determine how long immunity might last.
“The hope that we hold for this type of testing is that it may provide a better understanding of the spread of COVID-19 along with calculating accurate case fatality rates and developing other important indicators,” officials write. “Antibody testing may also prove useful for identifying first responders, medical providers and others who have been exposed and who can safely resume work without needing to be quarantined or isolated.”
St. John’s has tasked a group of local physicians, scientists, and experts with reviewing and advising on antibody testing platforms that may help the community. It will base decisions about antibody testing for healthcare workers and emergency responders on recommendations of the group. Members of the group have no financial interest in companies currently offering antibody testing, the letter says. The members of the panel are: Dr. Travis Riddell, Dr. Marcia Lux, Dr. Jim Little, Dr. Jeff Greenbaum, Dr. Lars Conway, Dr. Marc Domsky, Matt Lenz, Zach Hall, Laurentius Marais, and Chuck Fleischman.
The panel will consider several factors, including FDA approval status, technology specifications, published test performance, cost, invasiveness (blood draw vs. finger stick), impact on personal protective equipment (PPE) supplies in the community, and results of rigorously designed serology studies currently underway.
Until there is “a reliable antibody test,” St. John’s Health and Teton County Health Department agrees that PCR testing remains the priority.
“We feel strongly that we should continue first and foremost to direct available financial and human resources into doing more widespread COVID-19 active disease testing so that we can more quickly stop the spread of COVID-19 in our community,” the letter says. “It is the opinion of the Teton District Health Officer, the CEO of St. John’s Health, the Director of Teton County Health Department and other public health experts that antibody testing should not be the focus of the current effort to control the spread of COVID-19, but that we should conduct a robust exploration of whether antibody testing may soon be an important part of our public health response to this disease.”
