COVID-19 Test: What You Need to Know

January 14, 2022 4:00 pm

author:
University of Utah Health Communication

There are two types of tests: PCR and antigens.

The PCR test detects viral RNA. This is the type of test you must take at the test center. In the test, the tester uses a nasal swab or saliva to perform the test. The time required depends on the testing capabilities in your area, but in the event of a spike, it may take 24 hours to several days for results to be obtained.

Antigen testing (rapid testing) detects proteins on the surface of the virus. These tests are available in test centers and off-the-shelf kits. The results of these tests may be returned in just 15 minutes.

Both of these tests are useful, but it can be difficult to determine which is best for your particular situation.

Emily Spibak, MD, MHS, Associate Professor of Health Infectious Diseases, University of Utah, provides the following information on how to test, when to test, and which test is best.

Should I have a PCR or antigen (rapid) test if I suspect I have COVID-19?

Ideally PCR because it is more sensitive and accurate and is more likely to detect the COVID-19 virus. In reality, the demand for this type of test is currently very high due to the surge in Omicron, which can take several days before results are obtained. If this is the case in your area, a quick home test kit can help, given the good performance at the stage of symptoms, especially after 12 to 24 hours of symptoms.

If I have been infected with COVID-19, how many days do I need to be tested?

The recommendation is 3-5 days after exposure. Faster if you are symptomatic. If you have a high-risk exposure and the rapid test returns negative, it is best to follow up with the PCR test to completely rule out COVID-19 infection.

With a lack of tests and long lines, can you skip the tests and assume that you are simply infected with a virus if you are experiencing symptoms?

It is always best to test, especially if you are at high risk of serious illness, working in a medical facility, or interacting with a vulnerable population. However, if you have a high incidence of COVID-19 in your area, it is reasonable to assume that you have any symptoms. In case of illness, I add that it’s a good idea to stay at home, even if you don’t have COVID-19. Currently, our medical system is overwhelming. Isolate COVID-19, flu, or any other infectious disease if possible, and wear a high-quality mask whenever you need to go out in public.

Do rapid commercial tests detect COVID-19 as accurately as any other method?

Rapid testing is less sensitive than PCR testing, but it is about 90% more sensitive in the presence of symptoms. They are less sensitive in asymptomatic individuals. Also, if the rapid test is done too early, the virus will be less present and the result may be negative. Again, if the early symptomatic test gives a negative result, but you suspect that you are infected with COVID-19, repeat the test 24-48 hours later or do a PCR test.

Some people share on social media that when using a home test kit, you need to wipe your throat instead of your nose. Do you recommend it?

Some unpublished data suggest that sore throat is a common symptom in the early stages of infection. Also, viral replication by Omicron begins at high levels in the throat and can later travel to the nasal passages. This can result in a negative nasal test early in the symptoms. At this time, it is advisable to try saliva PCR testing early in the onset of symptoms or repeat the rapid antigen testing strategy.

People share an anecdote that wiping the throat or wiping the throat first and then the nostrils may give better results, but this is not currently recommended by test makers. .. Information is still available and needs to be investigated before recommending it.

Is the accuracy of rapid testing in detecting Omicron virus less accurate?

Still do not know. No research has been done yet, but as far as we know, rapid testing is still good at detecting Omicrons. However, the accuracy may be low on the first day of the symptom, so assume that you are infected with COVID-19 and wait for the test on the second day of the symptom, or repeat the test if the first is negative.

How accurate is the PCR test? Some people who test negative for PCR are convinced that they are infected with COVID-19. What advice would you give to someone who has a negative test but has symptoms of the disease?

The PCR test is very accurate, but not 100% accurate and depends on the accuracy of the sample collected. If you get negative results but have symptoms of COVID-19, isolate at home if possible and repeat the test within 24 hours. Also, be aware that other respiratory viruses are circulating in the community. It is also important to stay home to stop the infection of other viruses.

What if I need test results before undergoing another procedure such as surgery or a monoclonal antibody?

PCR tests are best, but if you need immediate results, some backups in your area may not be available. In this case, a quick test is recommended, but you should also check the requirements for a particular procedure. Talk to your healthcare provider about the best option.

If I have been infected with COVID-19 and are currently asymptomatic and 5 days have passed since the onset of symptoms, do I need to test again? Or is it safe to get back to work with a high quality mask?

Talk to your employer about your workplace requirements. Current CDC guidance recommends, but does not require, test if you can. If you are asymptomatic, you can return to work, but you should wear a high-quality mask such as KN95 for at least another 5 days. If you still have a fever or a severe cough after 5 days, stay in quarantine until your symptoms subside. It is important to note that a cough can last for days or weeks. Therefore, if your cough is productive and frequent, be careful. However, if it is a dry, intermittent cough and other symptoms go away, it may be safe to get out of isolation as long as you can continue to wear the mask.

My main advice right now is to get vaccinated, get a booster, use a high quality mask such as KN95, practice social distance, work from home if possible, get infected with the virus. It’s about testing if you suspect you’re doing it. If you can’t test but feel sick, isolate if possible. Many people describe the virus as less serious than other variants, but it’s not so serious for our medical system and some people in our hospital are very ill. If you get Omicron, don’t assume that you will have only mild symptoms.