Differences Between the 3 COVID-19 Tests

Published On: February 4, 2021Categories: Uncategorized
medical professionals

Urgent care clinics are familiar with upper respiratory viruses. In a 2016 survey, the top medical diagnoses given in urgent care centers were acute upper respiratory infections, acute sinusitis, acute pharyngitis, cough, and fever. These result from influenza, colds, and even previously discovered versions of the coronavirus.

But the novel coronavirus that causes COVID-19 is different. Although doctors have not definitively determined why its symptoms are so much worse, doctors do know that the outcomes are much more serious. Patients are at much higher risk of developing pneumonia from COVID-19 than flu. The result is a mortality rate that is at least three times higher than the flu.

Moreover, COVID-19 appears to spread more widely than the flu. The main reason is that the pre-symptomatic period during which a person can spread the virus before showing symptoms is about a day for the flu, but a whopping 14 days for COVID-19.

This fact highlights the need for testing. Medical professionals hope that extensive testing can help to identify these pre-symptomatic, but contagious people as quickly as possible so they can isolate. This minimizes, or even eliminates, the number of people they infect.

Three different COVID-19 tests are available. These tests work differently and are used in different situations. Here are the three types of COVID-19 tests and the general differences among them:

Molecular Test

This test is also called a PCR test because it uses PCR technology to examine the test sample for the DNA of the COVID-19 virus. This test is highly accurate but can take anywhere from a day to a week to complete depending on the location. This test only detects active COVID-19 infections, so it cannot be used to determine if you were previously infected.

Medical professionals use molecular tests to identify pre-symptomatic or asymptomatic cases so the person infected can isolate from others. This minimizes the risk of infecting friends, family, co-workers, and the public.

Molecular tests are also useful to distinguish COVID-19 cases from influenza or severe colds, which produce similar symptoms, but do not have the same grave consequences as COVID-19.

An urgent care administers the molecular test by taking a nasopharyngeal swab or collecting a saliva sample. The test sample is sent to a lab that uses a thermal cycler to amplify the DNA in the sample. This makes it easier for the lab to find the COVID-19 DNA in the sample. If the sample contains COVID-19 DNA, the test is positive.

Antigen Test

This test also requires a nasopharyngeal swab. Rather than being sent to a lab, the antigen test can be conducted at the testing location. The reason is that rather than requiring expensive DNA equipment, an antigen test only requires a test strip that detects the N protein on the surface of the COVID-19 virus’s molecule. Medical professionals use antigen tests to detect active infections. These tests cannot detect recovered cases.

The benefits of the antigen test are that it is much faster, much more convenient, and much less expensive than a molecular test.

The main disadvantage is the antigen test is much less sensitive than the molecular test. While positive test results are usually correct, the antigen test can produce false negatives when someone has a low viral load. This means that a negative result on an antigen test is not always negative.

Antibody Test

An antibody test looks for the presence of COVID-19 antibodies. The antibodies are produced by the immune system in response to a COVID-19 infection. Thus, rather than detecting the COVID-19 virus directly, it detects the virus indirectly.

Antibody tests require a blood sample and are used by medical professionals to identify previously recovered cases of COVID-19. Thus, this test is the only version currently in use that can tell you if you can return to work or school after recovering. This test cannot be used to identify a current infection.

These tests can be completed the same day, but can take up to three days depending on the lab.

COVID-19 testing will be a key element to ending the pandemic. But you must know how the tests are used what their weaknesses are so that you can get the right test for your situation. When you have questions about COVID-19 and any of the tests that are available, don’t hesitate to reach out to Care Station Medical.