How Well Do Rapid Tests Actually Work? Infectious Disease Experts Break It Down

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Infectious disease doctors break it down.

As convenient as rapid tests are, many people wonder about their accuracy. How often do people get false negatives? Is one brand better than another?

With so many people testing negative on rapid tests when they're actually positive—an experience a lot of people have had recently—it raises the question of whether this has something to do with this new variant. Here’s everything you need to know.

Why Some COVID Rapid Tests Show Negative Results Even if You’re Positive

There is no evidence to suggest that the new variants (XBB.1.5 or BQ.1.1 for example) lead to less accurate rapid tests. The rapid tests should still be working against the current variants, and we know that even as SARS-CoV-2 has evolved, the rapid tests have continued working for all prior variants, Dr. Scott Roberts, MD, a Yale Medicine infectious diseases specialist, explains.

However, Dr. Roberts says false negatives can appear on rapid tests for the following reasons:

  • The tests aren’t that sensitive (compared to PCR) and multiple tests over time may be required.
  • The user doesn’t test appropriately (not swabbing far back enough in the nose).
  • People are testing too early, often at the very start of symptoms, before the viral load has ramped up enough to flag a positive test.

Related: Do At-Home COVID Tests Expire? Here’s What Infectious Disease Experts Say

Dr. Henry Redel, MD, Chief of Infectious Disease, Saint Peter’s University Hospital in New Brunswick, New Jersey, agrees that the new variant isn’t a factor.

“People may not be doing the serial testing that is recommended—sometimes the antigen test may be negative early in disease so it is worth repeating 48-72 hours after an initial negative test following the manufacturer's protocol,” says Dr. Redel.

How Accurate Are Rapid COVID-19 Tests?

Rapid tests are accurate roughly three-quarters of the time when someone has symptoms, according to Dr. Roberts. This accuracy rate is a lot lower than a PCR test, which has a much higher sensitivity. For this reason, if you suspect you have COVID, either get a PCR test or repeat your rapid test 48 hours after your first negative. 

“There are multiple types of rapid tests including NAATs which are a bit more sensitive picking up in the range of 90% of cases, most are antigen-based which are not as sensitive as the PCR tests meaning they will miss some positive cases,” Dr. Redel explains. “They do pick up about 70% of cases when done appropriately and include the repeat testing.”

In other words, the brand does make a difference. "Some tests work better than others and some brands have been recalled by the FDA,” says Dr. Roberts. “I suggest ensuring that the rapid at-home test used is validated by the FDA.”

Because rapid tests can take days to show a positive result, if you suspect you have COVID, it's important to either get a PCR test to confirm or make sure you're isolating from others while you repeat rapid testing every 48 hours.  

Next up: Looking for an At-Home COVID Test? Here's Exactly Where to Get One

Sources

  • Scott Roberts, MD, a Yale Medicine infectious diseases specialist
  • Dr. Henry Redel, Chief of Infectious Disease, Saint Peter’s University Hospital in New Brunswick, NJ
  • FDA: “At-Home COVID-19 Antigen Tests-Take Steps to Reduce Your Risk of False Negative Results: FDA Safety Communication”
  • FDA: “At-Home OTC COVID-19 Diagnostic Tests”


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