02 Aug What To Do If You Get A Positive Antigen But Negative PCR Covid Test

The FDA has approved three specific tests for Covid-19; antigen, antibody, and PCR tests, but not without some cautionary footnotes. Specifically, it notes that antigen tests, while offering rapid results, can lead to false positives and false negatives. On the other hand, polymerase chain reaction (PCR) tests are considered the gold standard in viral testing because of their high sensitivity. Because of the relative inaccuracy of antigen tests, many people who use it might test one way, and then when they use a PCR test get different results. This article explains why you might get a positive antigen but negative PCR Covid test result and what to do.

Which test should you trust?

Covid-19 testing is currently the best way to arrest the spread of the virus. With widespread testing, it can be possible to identify those most likely to spread the virus, allowing them to self-isolate and protect those around them. It’s important to get the test most readily available to you if you think you may have Covid-19.

Before explaining why you might get differing results from antigen and PCR tests, you should know which test to trust and why.

Antigen testing vs. PCR testing

Antigen testing is a rapid testing method that looks for molecules (proteins) on the virus’s surface to generate a positive or negative result. Antigen tests are typically carried out in a non-lab environment and may be administered by anyone with some training. They can also be self-administered by someone who has no medical training with a DIY kit.

On the other hand, PCR testing is a lab test that looks for virus RNA, which are small pieces of genetic material that viruses use to create molecular proteins. Lab technicians carry out PCR tests in a sterile lab environment using sophisticated equipment that can detect even a single virus in a sample.

The verdict is that PCR tests are more reliable than antigen tests because they generally return a nearly 100% accurate result.

Positive antigen but negative PCR Covid test: What could be wrong?

So far, we’ve discussed situations in which individuals get a negative antigen test result but go on to have a positive PCR test result. In such cases, the antigen test missed detecting the virus, but the PCR test caught it.

In the case of a positive antigen test result that yields a negative PCR test result, however, the problem could have more to do with how the test was done.

Here are the main reasons this might happen:

• Sample contamination: If your sample is contaminated during testing, it might get mixed with another positive sample, leading to a positive result even though you might not have the virus.
• Wrong interpretation of results: If the person testing you makes a mistake interpreting the results, they might give you a positive result erroneously.
• Sample mix-up: In places that do lots of testing, it’s easy for samples to get mixed up, resulting in an individual getting test results that aren’t theirs.

In any of these scenarios, the positive antigen test result is overruled by a negative PCR test result because they are more accurate and less prone to such mistakes.

Related:

• Should You Get A Rapid PCR Test For Kids?
• What To Know About The 30-Minute Accula Rapid PCR Test
• How Accurate Are Rapid COVID-19 Tests?
• Can You Get A Rapid Covid-19 Test At Home With A Covid-19 Test Kit?
• What Is The RT-PCR Nasal Swab For Covid-19?
• What Is The Difference Between The Antibody And Antigen COVID-19 Tests?