As clinicians on the frontline of the COVID-19 pandemic, we know that accurate information is critically important for our patients. Facing an onslaught of misinformation about personal protection, symptoms, testing options, and treatment options, especially as the Delta variant continues to infect more people, the general public is left to wonder what’s real and what’s hype.
One active area of confusion surrounds COVID-19 testing. People want to know whether they have been infected, and they have other questions, such as “Are we still at risk if we were infected and recovered?” and “What are my options and risks today?” Also, new questions have arisen in recent weeks and months, such as “What is the need for testing if I’ve been vaccinated?” and “Does the Delta variant change anything regarding testing?”
Here’s what we know about COVID-19 testing and the Delta variant, including what you can expect as a vaccinated person.
Data suggests that the Delta variant is significantly more contagious than previous strains of COVID-19; however, it is not proving to be more deadly. The second surge is primarily affecting people who are not vaccinated — but vaccination is not a 100 percent guarantee against infection (vaccination provides very strong protection and has been shown to greatly decrease symptom severity, hospitalization, and death).
The CDC is now recommending that even if you are vaccinated, you should consider getting tested for the virus that causes COVID-19 if you have been exposed to someone who either is suspected to have or has been confirmed to have COVID-19 and you are showing symptoms of COVID-19, since you can pass on the infections to others.
There are many tests you can take to see if you may be actively infected with SARS-CoV-2 (the virus that causes COVID-19).
The two main types are nucleic acid amplification testing and rapid antigen testing, both available at many Carbon Health clinics. You can also find these tests in commercial testing centers like LabCorp or Quest, and through university healthcare centers.
NAATS specifically identify the RNA (ribonucleic acid) sequences that comprise the genetic material of the SARS-CoV-2 virus. NAATs can use many different methods to amplify nucleic acids and detect the virus, including but not limited to reverse transcription polymerase chain reaction (RT-PCR) and isothermal amplification.
Pros: NAATs are able to detect very small amounts of SARS-CoV-2 RNA in a specimen, making them highly sensitive and effective for diagnosing COVID-19.
Cons: To ensure accuracy, most test results may take days to a week for the average person to receive, although there are now rapid isothermal amplification tests that can be done within 30 minutes.
While NAATs look for genetic material from the virus, the antigen test looks for molecules on the surface of the virus.
Pros: Test results are almost immediate, allowing you to detect the presence of COVID-19 quickly.
Cons: These tests are less sensitive, with a higher false negative rate.
Positive results from both a NAAT and a rapid antigen test mean, with a high degree of certainty, that you are currently infected with SARS-CoV-2. However, a small percentage of people will still test positive with a NAAT six weeks after infection. If the person isn’t displaying any clinical symptoms of a COVID-19 infection, then it may be that they still have remnants of the virus RNA but are no longer infectious, or replicating viruses. (See current guidelines from the CDC on what to do when you are sick with COVID-19 or think you might have COVID-19.)
Testing negative with a NAAT is less reliable than testing positive. Again, because none of the tests have been studied in a clinical setting, about one in ten to about three in ten patients who test negative are actually positive carriers of SARS-CoV-2.
Rapid antigen tests are less sensitive than NAAT tests, so they have a higher false negative rate. They also are effective only during the peak period of infectivity, which is usually one to two days prior to symptoms and up to three to five days after symptom onset. After that, the false negative rate increases, which makes a NAAT test better at picking up positive tests for a longer period of time.
If you have been told your test is negative, you should still be careful about interacting with people, especially if they are at high risk or if you have symptoms that are consistent with COVID-19. It will take a while for us to know what the actual number of false negative tests are with any of these tests. Repeat testing is also an option for people who have symptoms — if medical professionals suspect COVID-19 despite a negative initial test.
An antibody test is most appropriate for people who need to know whether a recent illness was due to a coronavirus infection.
A positive serology or blood antibody test means you may have had a SARS-CoV-2 infection, or another type of coronavirus infection. However, antibodies can persist for a long time after infection and there are additional reasons for elevated antibodies, including the vaccine.
With the Delta variant, we are seeing infection in people who have already had COVID-19 and who have been vaccinated, so the presence of antibodies doesn’t mean that you cannot be infected. So at this time, antibody testing isn’t particularly useful for patients or clinicians. Researchers are constantly reviewing data to see whether this test could be useful in the future, in certain clinical settings or to guide booster needs in particular populations, but right now this does not appear to be the case.
At Carbon Health we are fully committed to making sure our patients get the care they need. We will update you about these tests as more information becomes available to the public. By getting ahead of the problem, we can flatten the curve together.
Carbon Health’s medical content is reviewed and approved by healthcare professionals before it is published. But note that our knowledge and understanding of COVID-19 are developing and changing very rapidly; if you have questions or concerns about COVID-19 precautions, treatments, and vaccinations, please talk to your healthcare provider.