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Covid-19 Rapid Antigen Test (RAT) – FAQ
Instructional video: How to do a Covid-19 Rapid Antigen Test (RAT)

General Information

Q: How accurate are Rapid Antigen Tests? 

A: Positive test results on rapid tests are generally accurate, and if you test positive you should take precautions (wear a high-quality respirator mask, isolate, inform your contacts) to avoid passing on the virus. 

A negative test doesn't necessarily mean your don't have Covid; it *could* mean you're not infected, but it may also mean that you don't yet have sufficient virus in your body for the test to detect. The higher the amount of virus (viral load) in the sample collected, the more likely the test will detect a Covid infection and the higher the risk that you can infect others. So you shouldn't rely on a single negative test to rule out Covid-19. Keep testing. If you have no symptoms, test 3 times, 48 hours apart. If you have symptoms, test twice, 48 hours apart.

Estimates of test sensitivity for older Omicron variants have been in the range of 70%–81%. It’s important to note that data isn’t available on newer circulating sub-variants. However as long as their mutations are targeting mainly the spike protein, rapid antigen tests which rely on detecting nucleocapsid protein, are still expected to work.

Q: How do I perform a rapid test? 

In early 2022, studies suggested that combined oral and nasal swabs are now more effective for detecting Covid infections. So in addition to the manufacturers’ instructions for your test kit, sampling should be modified as follows:

  • Perform an oral swab: rub the inside of each cheek, between the cheek and gums rotating the swab for 5 seconds and avoiding the teeth. Then rub the back of your throat or tongue for 5 seconds. Try to rub the soft tip at the very back of your throat. 
  • Next, perform a nasal swab: insert the swab into one nostril about 2 cm and gently swab around the inside of your nose 3-5 times. Repeat in the other nostril with the same swab. Swabbing shouldn’t be painful.
  • It’s important to read and interpret the test within the designated time window. Results outside this time period are invalid.

If you have symptoms

Q: When should I test if I have symptoms of Covid-19? 

A: You should test at the first sign of a viral illness. If your result is negative, test again in 48 hours. If still negative, repeat the test again in another 48 hours for a total of two 48 hour intervals. Serial testing at the start of a suspected Covid infection ensures the increase in the SARS-CoV-2 virus is captured, therefore increasing the chance the virus level will be above the detection limit of the test.  To verify your negative result, you may also consider using a different brand of rapid antigen tests. If you have symptoms, don’t rely on a single negative test to rule out Covid-19 though, assume you have an infection and take steps to prevent the transmission of all viral illness.

If you are in a high risk category and meet the BC eligibility criteria for Paxlovid (nirmatrelvir-ritonavir), we advise testing daily as the window to start Paxlovid is within 5 days of symptom onset (or if asymptomatic, 5 days of testing positive).

Q: Can a negative rapid test rule out Covid-19 completely?

A: No. Rapid tests are useful tools, but they do not detect all infections. You may also be early in your infection with a viral load too low for detection.

Q: I live and/or work alone and am not worried about spreading the virus to others. Do I still need to take a test? 

A: It’s a good idea to confirm your infection by rapid test. This way, you can document it for your medical record in case you develop Long Covid or a post-Covid condition in the future. Additionally, the timing of your next Covid vaccine will be changed based on the time since your last infection in order to have an ideal immune response. A three to six month interval is generally recommended by BC CDC, with the longer interval preferable. However, timing must be balanced with the risk of getting reinfected. 

Q: Can rapid tests be used after their expiry date?

Most rapid tests can be kept and used after their manufacturing dates. The manufacturing date is indicated on each test box next to the code MFG. Artron Covid-19 Antigen Tests, Abbott Panbio Nasal COVID-19 Rapid Test Device and the following lots of BTNX Inc. Rapid ResponseTM COVID-19 Antigen Rapid Test can be used 24 months after the manufacturing date.

Expired tests can be thrown in the garbage, and the cardboard box and instructions can be recycled.

If you’re visiting high-risk individuals

Q: How can I protect my high-risk loved one when visiting them?

A: When visiting a high-risk individual, such as an elderly person or someone who has underlying health conditions, is pregnant or has Long Covid, it is best to take a Covid-19
rapid antigen test as close to the time of your visit as possible (e.g., the morning of the visit if you will be visiting at lunch time). 

Keep in mind that you may have a negative result and still be infected, so continue to take other Covid precautions such as wearing a respirator-style mask. And if you have symptoms postpone your visit no matter the rapid test result.

Q: Are rapid tests necessary if I am fully vaccinated?

A: Yes. Although vaccines can reduce the risk of severe outcomes such as hospitalization and death, they do not prevent the spread of the highly transmissible sub-variants. Additionally in vaccinated individuals, symptoms can appear first (immune system reaction) with rapid tests being negative for a few days at the start of the infection. Thus the need to test every 48 hours after symptom onset, for two 48 hour intervals.

If you’ve been exposed to someone with Covid

Q: Can I test immediately after exposure?

A: It's generally recommended to wait 2 days after exposure before beginning to test. Omicron variants have a mean incubation period of 3.6 days, and testing too early may miss an infection that is just starting. 

Q: When can I stop testing after a high-risk exposure?

If you have no symptoms, you should continue testing every 48 hours. If negative, repeat in 48 hours. If the second test is negative, repeat one more time for a total of 3 intervals. 

Q: When am I not infectious anymore?

As long as your rapid antigen test remains positive, you should assume you can infect others. This is true regardless of the presence or absence of symptoms. Two negative tests 24 hours apart are best to ensure you are no longer infectious

A return of symptoms should prompt retesting as viral rebound does occur, meaning your symptoms return or worsen and you may test positive again after having tested negative. One small pre-print study suggested that it can happen in roughly 20% of individuals on Paxlovid treatment vs 2% of those not receiving it. Importantly, rebound was associated with being infectious for a prolonged period and thus a need to return to isolation and infection protection

In this same small study, only 50% of patients with a viral rebound experienced symptom rebound, suggesting the need for prolonged rapid antigen testing after Paxlovid. Unfortunately, how long one should continue to rapid test after a  Paxlovid treatment course, is unclear at this time.

Archived Briefings from Protect Our Province BC

In honor of February being Heart Month, cardiologist Dr. Leslie Kasza joined Protect our Province BC’s Dr. Susan Kuo for a discussion on COVID-19’s impact on heart health and how you can reduce your risk. Don’t be fooled into thinking it won’t happen to you because you are _________, fill in the blank: young, healthy vaccinated and/or you only had a mild infection, etc.
A Protect Our Province BC panel discussion about how we as a community, can pull together to create a safer learning environment for kids when school starts again in September! We can avoid another ‘tripledemic’ if we work together! Ready for Fall 2023? Briefing video:
“COVID-19 vaccination is safe during pregnancy and may protect newborns from infection, especially if vaccines are given in the second or third trimester. This is similar to what we are already doing with other maternal vaccines, including TDaP and seasonal influenza.” – Dr. Eastabrook

More News from Protect Our Province BC

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General Information Q: How accurate are Rapid Antigen Tests?  A: Positive test results on rapid tests are generally accurate, and if you test positive you should take precautions (wear a high-quality respirator mask, isolate, inform your contacts) to avoid passing on the virus.  A negative test doesn't necessarily mean your don't have Covid; it *could*… Continue reading Covid-19 Rapid Antigen Test (RAT) – FAQ