How Accurate Are Rapid COVID-19 Test Results?

How Accurate Are Rapid COVID-19 Test Results?

With the recent surge of the omicron COVID-19 variant in the United States, more and more people are procuring tests. While the PCR test is the most accurate way to detect COVID-19, it can be difficult to schedule an appointment. That’s why many people opt for the at-home rapid antigen tests. How accurate are these tests, which you can now obtain for free via the United States Postal Service?

Two types of tests can identify a current infection of SARS-CoV-2. The first test is the polymerase chain reaction (PCR) test, also called a diagnostic test or molecular test. This test identifies infection by detecting genetic material of the coronavirus. The second type of test is an antigen test, which diagnoses COVID-19 by searching for certain molecules found on the surface of SARS-CoV-2. Rapid antigen tests provide results quickly and don’t require lab analysis. Even though they yield quick results, they aren’t as accurate as PCR tests. 

How Accurate Are Rapid Antigen Tests?

The primary difference between a PCR and rapid antigen test is that rapid tests aren’t always sensitive enough to detect a positive infection. A PCR test may be able to detect positive infection sooner than a rapid test can, which helps reduce the spread of COVID-19. You can test negative with an antigen test, but there’s a possibility that you may be infected. The viral load may not be high enough for the test at that moment in time. People with symptoms may receive more accurate results.

If you want to test before getting together with a group of people, using a rapid antigen test may be sufficient. If you are traveling or attending an event, however, a PCR test is often necessary. According to the Centers for Disease Control and Prevention (CDC), antigen test sensitivity will vary depending on where you are in your infection. It has “moderate to high” sensitivity during peak viral load. That means that antigen tests are more likely to generate false negatives, especially on symptomless people.

Chances Or Rapid Tests Giving False Negatives

A 2021 review examined the results of 64 test accuracy studies that evaluated commercially produced molecular or rapid antigen tests. The results indicated that the accuracy varied considerably. For people with COVID-19 symptoms, the tests gave correct positive results 72% of the time. The average positive results for people with symptoms fell with the range of 63.7% to 79% accuracy. 

The accuracy for the antigen tests was different for people without COVID-19 symptoms. The researchers found that antigen tests had 58.1% accuracy for symptomless people. Researchers also used antigen tests during the first and second week of symptoms. Rapid antigen tests more accurately detected positive COVID-19 infection during the first week of symptoms. In fact the accuracy percentage was 78.3%, but it dropped to 51% accurate during the second week of symptoms. 

Are Some Rapid Tests Better Than Others?

In order for test makers to sell rapid test kits, they have to submit clinical data about the sensitivity and specificity of the test. Sensitivity relates to the test’s ability to detect a true positive, while specificity relates to the ability of the test to detect a true negative. The use of all at-home COVID-19 tests is allowed under emergency use from the U.S. Food and Drug Administration (FDA). For this reason, the relative performance of individual tests hasn’t been rigorously tested by the FDA. Is there one rapid test that is better or more reliable than another one? It’s very difficult or even possible to give an answer. 

Lastly, there is no rapid test that tells you which variant you have. In order to detect a variant, lab genetic testing is necessary. Random samples of positive COVID-19 are sent to specialized labs, where researchers anonymously sequence them to identify variants. Should you want the most accurate result for COVID-19 positivity or negativity, get a PCR test.

2022-05-13T04:23:34-07:00

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