A false positive result is possible with a rapid COVID-19 test. It happens when a person does not have COVID-19 but still tests positive for the disease.

People can use a rapid COVID-19 test at home to check whether they have SARS-CoV-2, the virus that causes COVID-19. The result is available within a few minutes.

These self-tests do not require laboratory analysis, and people can use one whether or not they are vaccinated or have any symptoms.

Rapid tests are available online, in pharmacies, or in retail stores. Other terms for a rapid test include a home test, an at-home test, or an over-the-counter (OTC) test.

This article outlines how a false positive on a rapid COVID-19 test can happen. It also discusses other factors, such as test accuracy and steps people should take if they test positive for COVID-19.

A person holding a false positive rapid covid test.Share on Pinterest
Design by Medical News Today; photography by Calvin Chan Wai Meng/Getty Images

Although a rapid COVID-19 test is unlikely to produce a false positive result, possible reasons for inaccurate results include:

  • Symptoms and testing time: Rapid tests tend to be more accurate if a person tests while experiencing some symptoms.
  • Contamination: The Food and Drug Administration (FDA) explains that false positive results can occur due to contamination.
  • Not reading instructions: People should read the package instructions before using an at-home COVID-19 test. A person may get a false positive result if they check the result before or after the test instructions recommend doing so.

According to the World Health Organization (WHO), rapid tests are less accurate than polymerase chain reaction (PCR) tests, which detect a virus’s genetic material. PCR tests check whether a person has the virus at the time they get tested and can provide an early diagnosis.

However, a rapid test has other advantages, which may outweigh the importance of sensitivity. These advantages include the below:

  • They are more easily available.
  • The results are ready faster.
  • They are cheaper and easier to do, making them suitable for frequent use.

A positive result on an at-home COVID-19 test is usually accurate, but false negatives can occur when a person has no COVID-19 symptoms or their infection happened recently.

A 2021 study found that antigen tests are more likely to be accurate if a person has a high viral load.

A 2020 pilot data study found rapid tests only detected around 48.9% of infections in people without symptoms. However, there is a low chance they will issue a false positive result.

Despite these drawbacks, some researchers have suggested that the speed of return and ability to do more frequent tests may make the rapid antigen test more suitable in many cases than a PCR test.

A person can take some measures to reduce the risk of getting a false positive test result, such as:

  • buying FDA-approved at-home tests
  • following the directions on the package
  • avoiding using expired tests
  • not sharing or reusing swabs

The FDA also provides a list of antigen tests that people can buy. These include:

  • Flowflex COVID-19 Antigen Home Test
  • NIDS COVID-19 Antigen Rapid Test Kit
  • OHC COVID-19 Antigen Self Test
  • QuickVue At-Home OTC COVID-19 Test
  • Celltrion DiaTrust COVID-19 Ag Home Test

The Centers for Disease Control and Prevention (CDC) recommend people take a rapid test if they:

  • have developed COVID-19 symptoms, such as cough, fatigue, shortness of breath, or nasal congestion
  • have been in close contact with someone who has contracted SARS-CoV-2
  • are attending an indoor or crowded event

If a person gets a positive result after an at-home test, they likely have COVID-19. If someone tests positive, the CDC recommends taking the following precautions:

  • staying at home for 5 days and avoiding close contact with others
  • staying hydrated
  • seeking medical care if an individual has trouble breathing
  • getting enough rest

The WHO recommends calling a medical professional if a person tests positive, has mild symptoms, and is at risk of developing a serious disease.

If a child tests positive for COVID-19, looks confused, and their lips turn blue — or gray or whitish for those with darker skin, a parent or caregiver should seek urgent care.

It may also be a suitable idea to undergo a PCR test to confirm the result.

A rapid or at-home COVID-19 test is a quick and convenient way to find out if a person has COVID-19.

Rarely, rapid tests may provide a false positive result. For example, if someone does not follow the package instructions, they may get inaccurate results.

Health experts recommend self-isolating for at least 5 days if they test positive for COVID-19. If a person experiences trouble breathing or worsening symptoms, they may wish to consult a doctor.