Experts explain the different kinds of COVID-19 tests

RT-PCR, antibody and antigen tests are the main COVID-19 tests available in El Paso

Maria Salette Ontiveros, Photographer

El Paso has been the focus of national media attention because of the staggering amount of new COVID-19 cases these past few weeks and it’s not letting up. The county reported Wednesday a record-shattering 3,100 new cases of COVID-19.

With the disease spreading like a wildfire, experts say it’s important to be educated on what kinds of COVID-19 tests are out there.

Currently, there are three different types of tests available in the region: The RT-PCR test, antibody test, and antigen test.

“The RT-PCR test detects directly the virus and is the most specific and sensitive test, it is the best. We call it the gold standard,” said Dr. Delfina Dominguez, clinical laboratory sciences professor at UTEP.

According to Dominguez, the PCR test detects even the smallest amounts of the virus because it’s the most sensitive.

“The antibody (test) just tells you if you have been infected or not… If the result is negative, it means that you have not developed in your body those proteins or antibodies of the coronavirus,” said Dr. Joel Hendryx, the chief medical officer at the University’s Medical Center of El Paso.

Hendryx explained there are times when people test positive for COVID-19 through both the antibody and RT-PCR tests without actually being infected. According to Hendryx, the person may have parts of the virus’ RNA are still floating around in their nasal area, which can be picked up because the PCR test is so sensitive.

He said that when this happens, a person has already had an immune response to the disease.

On the other hand, the antigen test looks for proteins from the virus.

“This antigen test is new and is being introduced very quickly, several laboratories have been approved by the FDA,” Dominguez said. “It is excellent in a way that is very specific, however, if the patient has low amounts of the virus, then they might be not detected either.”

According  to the Pan American Health Organization (PAHO) website, unlike previous rapid antibody tests, which have led to negative results during early stages of infection, this test is more accurate in determining if someone is infected.

“Sometimes people want to know as soon as possible, the antigen test takes 30 minutes and it is very fast, like I said, it’s very specific, but not that sensitive, in other words, the test can give you very good results if the patient contains high amount of the virus,” Domiguez said. “The antibody test is also very quick, but you can’t be certain if you are developing the antibodies which usually  develop after two weeks of the infection.”

The RT-PCR test takes three to five days to obtain results, the antibody test takes from 12 to 24 hours, while the antigen test takes half an hour. However, experts say the most efficient test citizens should take is the RT-PCR test.

The antibody test can be taken at any local clinic and the antigen test can be taken at any local laboratory.
There are currently four state testing sites in El Paso, open 9 a.m. to 4 p.m. Monday through Friday. The sites offer the RT-PCR test at no cost for anyone five years and older with or without symptoms.  No appointments are needed, but once the daily capacity is met, the site will close for the day.

Testing sites:

  • El Paso Community College Valle Verde Campus, 919 Hunter Dr., El Paso, TX
  • Nation Tobin Recreation Center, 8831 Railroad Dr., El Paso, TX
  • SISD Student Activities Complex, 1300 Joe Battle Blvd., El Paso, TX
  • UTEP Schuster 1 Parking Lot (Schuster Avenue and Spur 1966 Roundabout, on the south side of the complex), El Paso, TX
  • Ascarate Park, 6800 Delta, El Paso, TX

The UTEP testing program is free and available to UTEP staff, faculty and students who will be on campus during the semester. No appointments are necessary. The testing site  offers the RT-PCR test.

Maria Salette Ontiveros may be reached at [email protected]