Many of us have had a rapid antigen test (RAT) or administered it to our school-age children.
But how many of us are using them correctly?
Here are 15 pitfalls to avoid if you want to get the most out of your RAT.
1. Store at the wrong temperature
RATs must be kept at 2-30 degrees Celsius to work as intended.
Storing at higher temperatures means the proteins in the tests can become denatured: permanent changes to the protein’s structure, like when you cook an egg.
Don’t let the kit freeze. This can also damage kit components.
2. Use straight from the refrigerator
Reagents (essential test kit ingredients) will not function properly at low temperatures. Let the kit sit out of the fridge for about 30 minutes before using it.
3. Use an outdated test
Always check the expiration date before use, which you will find on the box. Expired tests may contain biological or chemical reagents that have been spiked or denatured.
4. Open too early
DO NOT open test items until you are ready to begin. Storing the open test can lead to false positives (you can test positive without actually having COVID).
5. Getting tested too soon or too late after exposure
One study, not yet peer-reviewed, suggests that RATs cannot detect SARS-CoV-2 (the virus that causes COVID-19) until at least day two after exposure. It takes an average of three days to test positive.
RATs are also unable to detect the virus after seven to eight days after exposure. So don’t wait too long to get tested.
RAT sensitivity (ability to detect a positive case) improves if you test daily, for several days.
6. Assuming all tests work the same
Some RATs need nasal swabs, others use saliva. The way the virus is extracted from the sample, the number of drops added to the test device, and the length of time to read the results differ between brands.
Familiarize yourself with the instructions, especially if it’s a brand new one or if it’s been a while since your last RAT.
7. Test contamination
DO NOT touch the tip of the swab (the soft piece that goes into the nose) with your fingers or allow it to come into contact with other surfaces.
8. Mucus sampling
Blow your nose before doing a nasal swab, as you don’t want to taste the mucus. You want to rub the tissue lining your nasal passages, using the technique below.
9. Cleaning with the swab at the wrong angle and depth
When you insert the nasal swab, you are not trying to swab the inside of the nostril, but the tissue further back in the nostrils.
So instead of going straight up with the swab, try going horizontally and about 2-3 centimeters back. Then roll the swab gently against the walls of your nasal passage the exact number of times your test recommends. Repeat on the other side.
Because it is easy to get the angle/depth wrong, it is best for parents or caregivers to take samples from children. Most RATs should not be used in children under two years of age, so check the instructions if you are not sure.
10. Continuing with a bloody swab
Blood on the nasal swab will give you an inaccurate result. Discard the test and do another when the bleeding has stopped, or take a sample only from the non-bleeding side.
Do not use a test that requires a nasal swab if you are prone to nosebleeds. Use a saliva test instead.
11. Eating, drinking, chewing gum, brushing teeth, or smoking before a saliva test
These may give an inaccurate result. So wait 30 minutes before taking a saliva sample.
12. Adding too many or too few drops to the indicating device
Adding the correct number of drops will ensure that the liquid moves across the test surface in a specified time. Adding too few or too many drops will mess up the timeline and the test will not work properly.
13. Reading the result too early or too late
Read the result at the time indicated in the instructions.
Read the test too soon and you may get a false negative result (the test is negative but you are really positive). Too late and it could indicate that you are positive when you are not.
14. Misinterpret the result
When you read your results (at the correct time):
two lines means you have tested positive for SARS-CoV-2
a line in C (for control) ONLY means the test worked and you tested negative
a line in T (for test) (or A for antigen, depending on the kit) but NOT in C means your test is faulty. make another
no lines also means your test is faulty and you need to repeat it.
15. Improper disposal of the kit
Seal any kit components that have been in contact with your nasal or saliva sample (swab, containers, reagents, test device, etc.) in the plastic bag provided and dispose of in the trash.
Just put the cardboard box and paper instructions in recycling.