Rapid Antigen vs PCR Test: Differences & Common Mistakes

Rapid Antigen vs PCR

After two years living with the Covid 19 pandemic, the world is ready to move on. But we do need to take proper precautions if we want to prevent another wave. CDC Guidelines recommend rapid testing, vaccinations, sanitization, and personal protective equipment as the tools and medical supplies that will enable us to return to our everyday lives.


One of the best ways to screen and diagnose people with the Covid 19 infection is using Covid-19 At Home Tests. Buying a rapid antigen test kit means that you can do the test in the safety, comfort and convenience of your own home or workplace. The other alternative, PCR testing, requires you to travel to a lab or testing site to give your sample and may take days to deliver your results.

An over-the-counter rapid antigen test is an easy solution and a handy medical supply to keep on hand!


What are the steps in taking a rapid antigen test?


Before you begin, it’s always important to look at the instructions as some tests can be different. Ensure you wash your hands thoroughly with warm water and soap for 30 seconds before handling any test components.


When you open a test kit, you will usually find:


  1. A swab stick individually wrapped in sterile plastic packaging
  2. A small vial/bottle/plastic container with a cap containing a clear liquid called the buffer solution
  3. A test strip, which is a small plastic cartridge with a well or slight depression, where you can put in the drops of the sample to be tested



Step 1: Taking the Sample Swabs


Open the test kit and line up the contents on a clean surface. Open the sterile packet containing the swab stick. Insert the collection swab into each nostril, rotating five times in each nostril.

It is advisable to insert the swab stick about 1/2 to 3/4 of an inch into each nostril. An easy way to figure out how deep to go is to measure the size of the tip of your little finger.


Some kits have two swab sticks, one for a nasal and one for a throat swab ( or an oropharyngeal swab). If there is a throat swab, you can insert it in your mouth and scrape the soft tip against the mucous lining at the back of your throat, at least 3-4 times.


The swab itself doesn’t hurt, but it can be uncomfortable, especially for people who have a sensitive gag reflex. It may cause a bout of sneezing or coughing after the test.

After you have finished, you can put the swabs back into their wrappers for later use.



Step 2: Mixing with the Buffer Solution


Tap the small plastic vial ( dropper or container) three times on a hard surface to eliminate any air bubbles. Remove the cap and set it aside on a clean surface.

Remove the swab sticks used to collect the sample from your nose or throat and insert the swab tip into the vial. Turn it around in the liquid at the bottom of the tube to mix it thoroughly. Squeeze the bottom of the vial as you pull out the swab to get every last bit of the sample you collected on your swab tip. Replace the cap on the vial and set it aside for 5 minutes. Throw away your swab safely.


Step 3: Loading the sample


The test cartridge has a sample collection well on one end. Remove the cap on the vial and place 3-5 drops of the liquid into the collection well.


Step 4: Interpreting the test


The test strip has two markings, a C and a T. As the liquid travels along the test strip, it reacts with the test chemicals. It forms a dark line visible at the marking for C. It is imperative to get a line at C, as this is the control line and lets you know that the test was done correctly. If there is no line at C, you must re-do the test.

Once the line is visible at the C mark, you must wait for 15-20 minutes.

If the Covid virus is present in your sample, and if you are positive, a line will be visible at the T marking.


Rapid Antigen vs PCR

A negative test result with a control line, which means the test was performed correctly.


Step 5: Precautions after a positive test


Discard all the test equipment properly. If your test is positive, be sure to isolate yourself from your friends and family and maintain proper precautions, including washing your hands and wearing masks. If your symptoms worsen, go to your local emergency department.


What are the common mistakes people make when doing a rapid antigen test?


A rapid antigen test is simple to perform, but people often make a few mistakes.


  1. They may not insert the swab deep enough into each nostril or into the back of the throat. This means that they may not get enough of the sample on the swab, and it may lead to a false-negative result.
  2. They may not mix the swab with the buffer solution well enough.
  3. They may not wait for 15-20 minutes before reading the results.


While they are minor steps, they are crucial to ensuring that the test is conducted correctly to give an accurate result.



What makes rapid antigen tests different from RT-PCR tests?


PCR ( polymerase chain reaction tests) are also known as nucleic acid-based tests, which detect the virus’s genetic material. On the other hand, rapid antigen tests detect protein particles on the virus’s surface.

Aside from the test mechanism, there are several other differences between rapid tests and PCR tests. Check out the table below to know more.


Rapid Antigen Tests

PCR tests

This is a point of care test that can be done anytime and anywhere. It comes with a clear set of instructions that enables anyone to do it, not just medical professionals.

This is a specialized test, where the sample collected is transported to a central laboratory where it is loaded in complex machines or analyzers to give a result.

It tells you whether the virus is present in high concentrations

It can detect whether any viral genetic material is present, even at low levels.

You can get these results in minutes and are cost-effective solutions for screening and diagnosing an infection.

They do take hours or days to give a result and are relatively expensive, which may not be effective as a screening tool.



When are rapid antigen tests used?


1. They are effective as screening tests.


People are going back to work, and children are going back to school, so screening employees and students with a fast and convenient rapid test are recommended to keep people safe from an outbreak. Early detection means that you can make efforts to sanitize and quarantine to limit the spread of the infection.


2. They are effective as diagnostic tests.


The rapid tests work by detecting specific proteins known as antigens on the surface of the covid virus particles. Unlike the PCR tests, these rapid kits don’t amplify what’s in the sample, so they can detect the virus only when it reaches a high enough level in your body. The virus usually comes to these levels around the time symptoms start and when you are likely to be most contagious. So, an excellent time to take these tests is when you start having symptoms.


With the spread of the Covid 19 infection, the demand for rapid kits has considerably increased as they provide a fast and easy way to test people for the infection. After buying and using rapid antigen test kits, you can recognize exposure risks, implement quarantine protocols, and safeguard the health of your family members, employees, or students, quickly and effectively.


At Peach Medical Labs, we have a full range of best-selling products, including Covid-19 Antigen Tests like the Abbott BinaxNOW at-home test, Quidel Quick Vue, and other OTC Covid Testing kits. They are known for their effectiveness in rapid testing of Covid 19. With easy instructions for the BinaxNOW kits, the BinaxNOW antigen self-test accuracy is one of the best!