TagAntibody Test

Types of COVID Tests

Getting tested for COVID can be confusing. 

Dr. Nirav Shah, senior scholar at Stanford University School of Medicine, describes the three different COVID tests available today: PCR, serology or antibody, and antigen tests.

At Covid Act Now, we hope that this post will give you a clear understanding of which COVID test to get, when to get tested, and how to evaluate the advantages, costs, and disadvantages of each.

PCR TESTS (Polymerase Chain Reaction)

The most widely used COVID test is called the PCR test. The PCR test is a nasal swab procedure that detects the viral genetic material of the virus. Lately, the delays to get the test results back for a PCR test can take up to a week, but these are the best tests available to detect if you have an active infection.

PCR tests are the most accurate COVID test for an active infection and cost over $100. There is generally a long wait for free testing with up to one-week turnaround times for results.

SEROLOGY TESTS

Serology tests, or, as they are more commonly known, “antibody tests,” test the blood and looks for antibodies, the proteins your body makes to fight the future infection. Antibodies are formed when you have an infection, whether or not you’ve had symptoms. 

It takes typically one to three weeks after infection for your body to make antibodies, and, as of today, we do not know how long the COVID antibodies can last in your body. 

Detection of COVID antibodies in the blood might indicate temporary immunization from the virus, but there is no definite proof so far. 

ANTIGEN TESTS

While the PCR and serology tests have pretty good test characteristics, such as sensitivity and specificity, the antigen tests are not as sensitive. This difference means that if an antibody test comes back negative, you may still have COVID. Antigen tests are generally used to confirm COVID positive diagnoses, but not to rule them out.

The antigen test is great to confirm COVID symptoms, as the PCR test results might take too long, and you might expose a lot of people during this turnaround time.

Antigen COVID tests give fast results (15 minutes), and do not have to be done in a lab or by highly trained personnel. They are inexpensive but can give false negatives, so antigen tests are best used to confirm symptoms.

Learn our 5 metrics: daily new cases, test positivity, infection rate, ICU headroom used, and contact tracing. For a description of assumptions and methodology, please see our references and assumptions document, along with our data sources presentation.

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