COVID-19 rapid tests, or antigen tests, are increasing in popularity to detect SARS-CoV-2 (novel coronavirus). UC Davis Health experts offer information below about COVID rapid tests and how they work.

Until now, the majority of COVID-19 rapid diagnostic tests have been done with a nasal or throat swab. They detect a protein that is part of the coronavirus. These rapid tests are particularly useful for identifying a person who is at or near peak infection. COVID-19 (novel coronavirus) replicates itself by putting its genetic material inside our cells. If a person is being tested at the stage, when the virus is still replicating inside the cells, the coronavirus has not produced sufficient protein or shed enough to be detected by antigen testing.

Antigen tests – or rapid tests – are less expensive and generally faster. The downside is they can be less accurate. As of November, UC Davis Health has a rapid test that is highly accurate for COVID-19 and the flu. This test is used for patients with symptoms, where we need to know what’s causing those symptoms in order to better treat the patient.

Learn more about COVID-19 testing

View a list of COVID-19 symptoms you should watch for

Antigen tests are known to be less sensitive than viral tests. These COVID rapid tests perform best with people in the early stages of COVID-19 infection, when viral load is the highest. Rapid tests are less expensive than the more accurate genetic tests and can be available at point-of-care.

No test is completely accurate, which means that some cases will be missed (false negatives) and some people will be told they have the virus when they don’t (false positives). Positive tests tend to be accurate, but negative tests need to be interpreted with caution, especially in a high-risk setting or when used on asymptomatic people. However, some experts argue that widespread testing, even when it’s less accurate, can still help contain the COVID-19 pandemic – especially if the test is regularly repeated, which is usually the case for these kinds of tests.

As of November, UC Davis Health has a rapid test that is highly accurate. This test is used for patients with symptoms, where we need to know what’s causing those symptoms in order to better treat the patient.

Learn more about rapid COVID tests

The Healthy Davis Together project has some COVID-19 testing options available for people who live in the City of Davis. For testing in Sacramento and other counties, you should check with your county’s public health office. Sacramento County offers a number of testing sites and options, though not necessarily rapid COVID tests. Testing options are also available in Placer County, El Dorado County and most other counties.

UC Davis Health rolled out a groundbreaking, highly accurate test that can check for both COVID-19 and flu viruses at the same time. It returns results in 20 minutes. We are the first in the region and among the first in the nation to use this rapid, combined molecular tests at the point of care. UC Davis Health was one of the institutions that helped evaluate the accuracy of these rapid tests to gain emergency use authorization from the U.S. Food and Drug Administration (FDA). We are also the first UC health system to use the rapid flu and COVID-19 test.

The rapid point-of-care test is a PCR-based method, which is similar to what UC Davis Health has used in our lab since March where we run hundreds of tests a day. The accuracy is greater than 99% and often returns results in less than an hour. What’s new is the combination of accuracy and speed, plus the ease of a single test to detect the COVID-19 (novel coronavirus) and A and B flu viruses.

Both the rapid COVID-19/flu test and the lab test for COVID-19 are highly sensitive, highly specific PCR tests. They can pick up very small amounts of viral RNA very early in an infection, so there’s a low chance for false negatives, including among pre-symptomatic and asymptomatic COVID-19 cases. The lab tests are run in a fully enclosed robot and operated by highly trained clinical laboratory scientists, so there’s little chance of cross-contamination or human error.

For now, the combined COVID-19 and flu tests will be limited to the emergency department or situations when speed is critical to understand a patient’s condition. Fast, accurate flu and COVID-19 results can help with management and treatment of both viruses. They can also eliminate hours or sometimes days of anxiety for patients.

Most UC Davis Health patients will continue to get the molecular PCR tests that come back in about a day. This is because the flu/COVID rapid tests, for now, are being used in the emergency department and in clinics where results are time sensitive.

Testing through UC Davis Health is for:

  • patients with symptoms
  • patients who need treatment in order to help manage their health, or
  • people who are being admitted to UC Davis Medical Center for a procedure or other condition

Read more about the rapid test for flu and COVID-19