Coronavirus Chronicles

What to Know about Rapid Covid Tests in King County

Tests are back on the rise. But is it any easier to get a quick and reliable result?

By Benjamin Cassidy September 16, 2021

Uh, what did the directions say?

Everyone's getting Covid tests again in King County. After a precipitous drop in swabbing that coincided with the widespread uptake of vaccines, daily test counts in the area are back at winter-wave levels.

And those numbers are probably undercounts. Unlike at earlier points of the pandemic, at-home rapid Covid tests are popping up in stores and internet search results. In just 15 minutes, these kits can offer peace of mind as people venture out into a world where the Delta variant is spreading. Or, they can very quickly alert someone that they're infected, potentially thwarting superspreader events before they start.

But are they really reliable? And where can people find them? With some help from Public Health—Seattle and King County, we've got answers.

What is a rapid Covid test?

Let's start with this: "rapid Covid test" is a bit of a misnomer. The test itself isn't any quicker than the old-fashioned swabbing we all came to expect at the beginning of the pandemic. It's the results of that test that arrive faster. Rapid Covid tests pick up viral antigens, or particles of SARS-CoV-2, rather than its genetic material, King County's public health authority explains. This is a quicker task: It takes just 15–30 minutes to figure out if someone's Covid-positive.

Are these the at-home Covid tests everyone's talking about?

Yes, most likely. At-home PCR tests are far less common.

PCR? What is a PCR test?

If you've visited a testing site and had to wait a few days for your results, you've likely had a polymerase chain reaction test. These swabs do identify the virus's genetic material, but they need to be lab-processed, hence the delay in getting a Covid yea or nay.

Wait, why haven't we been using rapid tests at every site instead of PCR tests?

PCR tests "are considered the gold standard for accuracy and sensitivity," Public Health—Seattle and King County's Gabriel Spitzer notes via email.

So are the rapid tests unreliable?

Spitzer says rapid tests are sometimes less accurate than the PCR tests "depending on whether a person is vaccinated or not and whether a person has symptoms." False positives may be less common. "A positive result from a rapid test is usually highly accurate, but a negative test cannot completely rule out an infection, especially if the person is unvaccinated or has symptoms."

But if you get two negative rapid test results within 48 hours, you can consider yourself negative.

Shouldn't people just get the PCR test, then?

As mentioned, PCR tests take multiple days to process. Sometimes people need answers sooner than that if they want to minimize potential spread of the virus (see: sports). Difficulty booking a PCR appointment (or waiting in an absurdly long line) is also increasingly common. Basically, it's a much slower process. For the record: Public Health—Seattle and King County doesn't officially recommend one test over the other.

Where can people get a Covid test in King County?

Some original Covid testing sites may be closed now. It's best to check this running list for sites across King County.

Okay, maybe the rapid Covid test will be more convenient, actually. What happens if you test positive?

Whether you're vaccinated or unvaccinated, you should isolate for 10 days from the time you first experience symptoms. Didn't have any symptoms? Isolate for 10 days post-positive test. Also, you should tell any close contacts and your medical provider about your positive test. Though not required, you are strongly encouraged to report your positive result to Washington's Department of Health by calling 1-800-525-1027.

Some rapid Covid kits include two tests. What happens if one test produces a positive result and the other a negative?

As mentioned before, false negatives can occur; taking a third test within 48 hours can help confirm that the negative is a true negative. Symptomatic people who test negative very likely do not have Covid; rapid tests are less reliable in asymptomatic people. When in doubt, isolate.

How much do rapid Covid tests cost?

It's not cheap; $10 or $15 per test on the lower end, but they can run you much more. With demand high, expect it to be expensive. There are various types of rapid tests available, but Washington high school athletes are using BinaxNOW, a common one that can be found at pharmacies.

Will venues and/or businesses accept a negative result from a rapid Covid test?

Best to check with the business or venue.

How does self-swabbing work?

That's what directions are for.

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