Different Types of COVID-19 Tests

Different Types of COVID-19 Tests

With the abrupt arrival of the highly contagious Omicron variant just before the holiday season, the world is heading into 2022 — and the third year of the coronavirus pandemic — in the midst of a record-breaking wave of COVID-19 cases. 

Given that Omicron appears to be causing a rapid surge in infections among unvaccinated and vaccinated people alike, it’s as important as ever to get tested at the onset of worrisome symptoms or after an incident of close-contact exposure. 

Here at American River Urgent Care in Orangevale, California, we offer convenient on-site COVID-19 testing — including molecular PCR tests and rapid antigen tests — to people of all ages. Here’s what you should know about these two basic diagnostic methods.   

Diagnostic COVID-19 testing

During the past two years of sporadic lockdowns, social distancing, mask wearing, remote work, distance learning, vaccinations, and boosters, scientists were busy creating a variety of COVID-19 tests to help people detect active infections as quickly and accurately as possible.

But while it may seem like there are many available testing options, all diagnostic COVID tests fall into two basic categories: PCR tests and antigen tests. 

Molecular PCR testing

The FDA authorized the first PCR test back in March 2020. Early on, these deep nasal swab tests were typically administered by healthcare professionals at drive-through testing hubs.   

How it works

The coronavirus replicates itself by putting its genetic material inside your cells; a molecular PCR test uses polymerase chain reaction technology to detect trace amounts of that genetic material.

This COVID test isolates viral RNA from a nasal swab, throat swab, or saliva sample, and then converts it into a complementary strand of DNA. Next, using the PCR technique, the DNA is multiplied thousands of times to create a sample that’s large enough to analyze.  

Advantages

Considered the gold-standard diagnostic test for COVID-19, PCR tests are exceptionally sensitive: positive results are almost always correct, and false negatives are extremely rare. This high level of sensitivity means that PCR tests are very reliable.   

Downsides

Because PCR tests must be sent to a lab for processing, it can take anywhere from 24 hours to several days to get results. While their outstanding accuracy is valuable, having to wait for them can be problematic — especially if it’s difficult for you to quarantine in the meantime.     

Best application

PCR tests are always the best choice if you’re able to quarantine until you receive your results. They’re not a good option, however, if you need to know your infection status as soon as possible. In such cases, it’s best to take a rapid antigen test first, then follow up with a PCR test to confirm your results.   

Rapid antigen testing 

First approved by the FDA in May 2020, rapid antigen tests are simpler, less expensive, and often more accessible than PCR tests. They’re specifically designed to detect active coronavirus infections quickly and with a relatively reliable rate of accuracy. 

How it works

COVID sheds proteins as it replicates inside your body. Antigen tests detect fragments of these viral proteins, typically from a sample collected via nasal swab or throat swab. 

The swabbed sample is mixed with a liquid and placed onto a testing strip. As the mixture flows across the strip, the COVID antibodies that are present in the strip bind to any viral protein fragments that are present in the sample. 

If there are COVID proteins in the sample, the bonded protein-antibody complex forms a visible, colored line. If there are no viral proteins, or if levels aren’t yet high enough to detect, there’s no line. 

Advantages

Antigen tests offer quick results, often in a matter of minutes and usually in less than an hour. They’re very good at detecting COVID infections that are near their peak, and they rarely generate false positives. This means that if an antigen test says you test positive, you very likely have an active COVID infection.

Downsides

Antigen tests aren’t as sensitive as PCR tests, meaning they’re more likely to generate false negatives. This means that a negative antigen test doesn’t definitively rule out the presence of an active COVID infection. Antigen tests are also less likely to detect an active infection in its earliest stage, when viral loads are low.  

Best application

Antigen tests are very useful for diagnosing an active COVID infection in real time, particularly when symptoms are present or following a known exposure. But if the test generates a negative result — especially if you have symptoms or you’ve been exposed — it’s best to double-check the result with a PCR test. 

Schedule your COVID test today

Whether you’re experiencing symptoms, you want to check your status following an exposure, or you’d simply like to be tested prior to an event or family visit, we can help. Call 916-287-8569 to schedule a prompt PCR or rapid antigen test at American River Urgent Care today, or click online to book an appointment any time.

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