PHOENIX (April 30, 2020)—With more COVID-19 testing options available, residents need to be aware of how testing options vary and what information they do and do not provide. The two main types of tests currently available answer two different questions:
- A PCR test is used to determine if someone is currently infected with COVID-19
- A serology test is used to determine if someone has been infected with COVID-19 recently or in the past
“The two main questions people want to know are, am I sick with COVID-19 right now, and have I had it already," said Dr. Rebecca Sunenshine, medical director for disease control at Maricopa County Department of Public Health. “The first question is easier to answer, but you need the right type of test to answer that specific question.”
A PCR test (polymerase chain reaction test) is a diagnostic test that determines if someone is currently infected with COVID-19 by detecting the genetic material of the disease. This is the test that has been available since the start of the outbreak, is used by most healthcare providers to diagnose the disease and the one reported to Maricopa County Public Health where we get our daily numbers of confirmed cases.
Antibody testing, also known as serology, is less useful as a diagnostic test to determine if someone is currently infected. Instead of looking for the genetic material of the virus, serology testing looks for antibodies created by the body to fight infection to determine if the person was recently infected or infected in the past. Because it takes some time for the body to develop these antibodies, it is not as reliable for diagnosing active infection or for making clinical recommendations for care.
There isn’t enough information available about the test yet to know whether a positive serology test means that someone definitely had COVID-19 in the past because the test may detect antibodies to related-but-different coronavirus strains that cause the common cold.
Dr. Sunenshine explained, “It’s like seeing someone at a party who at first glance you think is your friend, but then it turns out to be their cousin who just looks really similar. Even though they look almost the same, the antibodies wouldn’t protect you from getting COVID-19.” She added, “We don’t want people to believe they are immune to COVID-19 and stop doing the things they need to do to protect themselves like washing their hands and staying 6 feet away from others.”
Anyone who has symptoms of COVID-19 or thinks they may have been exposed should call a healthcare provider or use the CDC symptom checker at Maricopa.gov/COVID19. In that case, PCR testing is the most appropriate test.
People who are curious about whether they have had COVID-19 in the past can ask for a serology test. They should continue to protect themselves, regardless of the result.
- Wash your hands with soap and water frequently
- Don’t touch your face
- Stay at least 6 feet away from others
- Stay home and away from others if you are sick
If you think you might be sick with COVID-19 or have been exposed to COVID-19, please immediately isolate yourself from others in your household. CDC recently added additional COVID-19 symptoms to the list in addition to cough and difficulty breathing. These include:
- Fever
- Chills
- Repeated shaking with chills
- Muscle pain
- Headache
- Sore throat
- New loss of taste or smell
If you are sick, have been around someone who is sick or are caring for someone who is sick, please see https://www.maricopa.gov/5512/Sick-or-Exposed-to-COVID-19 for details on what you can do to protect yourself and those around you.
For more information on COVID-19 and what you can do to stop the spread, please visit www.Maricopa.gov/COVID19 for English or www.Maricopa.gov/COVID19es for Spanish.