Difference Between Rapid Antigen Test, RT-PCR And Antibody Test For COVID

Travel restrictions due to COVID-19 are still in place all over the globe, which is one of the main reasons why COVID tests are still a necessity. 

Rapid antigen tests and RT-PCR tests have become necessary almost worldwide, and this is especially true for travelers. 

Whether you have to travel for work, family obligations, or for pleasure - you’ll need a COVID test to travel. Even if you can get into a country without a COVID test, you might need a negative COVID test in order to get back into your country. 

Advancements in technology have allowed healthcare professionals to make COVID tests widely available for our safety.

Diagnostic (viral) COVID tests help you determine your positive or negative COVID status, which helps you decipher if it’s safe to travel, be around other people, go to work, or attend social events.

COVID-19 is often characterized by symptoms such as fever, cough, sore throat, body aches, loss of the sense of taste or smell, fatigue, shortness of breath - just to name a few. However, sometimes COVID-19 is present with zero symptoms. 

The two most common laboratory tests to test your COVID status are RT-PCR and rapid antigen tests. 

Project Screen, delivers world-leading SARS-CoV-2 testing solutions, including both RT-PCR testing for pre-departure and peace of mind, as well as at-home antigen testing with the FlowflexTM  COVID-19 Rapid Antigen Test.

Meanwhile, an antibody test, which is usually a blood test, identifies how many antibodies your immune system has produced to fight against COVID-19, due to a previous COVID-19 infection or vaccination. This indicates you may have immunity against COVID-19. However, antibody tests are not suitable for diagnosing an active COVID-19 infection.

When should you be using an antigen test, RT-PCR test, or an antibody test? Below, we will provide an overview on all three types of COVID tests, the difference between them, and a guide on which best suits your needs.

1. Rapid Antigen Test

Antigen tests such as the FlowflexTM COVID-19 Rapid Antigen Test are immunoassays designed to detect specific COVID-19 viral antigens. Point-of-care, laboratory-based, and self-tests are currently authorized for use. They can be performed on nasal or nasopharyngeal swab specimens placed directly into the extraction buffer or reagent.

Antigen tests for severe acute respiratory syndrome coronavirus (SARS-CoV) are affordable, fast, and suitable for people of any age. Most antigen tests return results in approximately 15–30 minutes. These rapid COVID tests tend to be less sensitive than other nucleic acid amplification tests, which detect and amplify the presence of viral nucleic acid. However, nucleic acid amplification tests (NAATs) can produce positive results several weeks after initial infection. They can detect levels of viral nucleic acid even when the virus cannot be cultured. This shows that a positive result does not always indicate contagiousness.

Because antigen tests are less sensitive, additional testing with NAAT is recommended. However, where rapid test turnaround time is critical and immediate results are desired, antigen tests may be used to screen for the presence or absence of this pathogen. This early detection enables infection prevention and control measures to be initiated, preventing transmission.

Antigen tests are faster, more convenient, and cheaper than a RT-PCR test, but are they as accurate? Let’s discuss RT-PCR tests below.

2. RT-PCR Test

Many people often feel inconvenienced when they have to get a RT-PCR test. However, the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) test is the gold standard for diagnosing viral diseases like COVID-19. 

The RT-PCR test isn’t quite as convenient as a PCR test, but it’s extremely accurate, and a correct diagnosis from a PCR test is almost guaranteed. This means that there is a high possibility of a positive result for those who have the virus. However, there is still a small chance of misinterpretation and incorrectly diagnosing someone as positive when they are, in fact, negative. The rapid antigen test typically has an analytic sensitivity of 30% to 40% lower than RT-PCR test, depending on whether the tested people are symptomatic or asymptomatic. 

Sometimes, depending on the situation, it’s serious enough that you need an RT-PCR test instead of a rapid test.

How The RT-PCR Test is Conducted

The clinician begins the RT-PCR test by using a long, soft swab to collect a sample of respiratory secretions from the back of the nasal cavity. This sample is then treated with chemicals to extract viral RNA. If a person is infected with a virus, the sample will have both their DNA and the virus' RNA. The reverse transcriptase enzyme, which stands for RT, converts RNA extracted from a sample into DNA. This conversion is necessary because the virus that causes COVID-19 is a single-stranded RNA-based virus and cannot be amplified without being changed into double-stranded DNA.

The next step with this type of COVID test involves identifying the virus utilizing fluorescent dye identification through the viral DNA amplification process. A specialized device tracks the amount of fluorescence in the sample after each cycle of amplification and presents what is measured in real time on the computer. The result is then examined and determined as positive or negative. Amplifying viral genetic material is a lengthier process. 

One of the less convenient aspects of this type of test is that when you get a RT-PCR test, you might not get your test results for 24 hours or longer. On the other hand, antigen tests such as the at-home FlowflexTM COVID-19 Rapid Antigen Test yield results in around 15 minutes to detect the presence of antigens on the surface of the coronavirus. 

3. Antibody Test

Antibody (or serology) tests use your blood sample to look for antibodies that your immune system produced in response to a COVID-19 infection or vaccination. COVID-19 antibodies are a marker for protection from the virus and often help prevent infections. Therefore, antibodies may play an instrumental role in preventing severe symptoms, hospitalisation, and death caused by COVID-19. However, the presence of antibodies in your immune system cannot guarantee that you will not become infected or re-infected with COVID-19.  

Even if your immune system has produced antibodies, they decline over time. The rate at which they decline also varies from person to person. Taking an antibody test can determine your current antibody levels and indicate if they may be sufficient to protect your body from severe COVID-19 symptoms.

Keep in mind, antibody tests are not suitable for diagnosis whether you currently have a COVID-19 infection and should not be used to check for immunity. More research is needed to determine what these tests can tell us about a person’s immunity.

What To Do If You Think You Might Have COVID

If you think you have COVID symptoms, you’ve been around someone who was tested positive for COVID, or you simply suspect you may have COVID, follow the steps outlined by the CDC below to care for yourself and others:

• Most patients who have mild symptoms of COVID-19 can recover at home without medical care. However, to protect others, avoid going to crowded places such as grocery stores or sporting events.
• Self-isolate and practice social distancing.
• It is recommended that you get rest, drink plenty of fluids and take over-the-counter medication to help you feel better, such as acetaminophen for body aches. 
• The best way to avoid further exposure is to remain in a single room of your home and avoid being with others. This means that if you don’t live alone, try to use separate utensils and a separate bathroom. Wear a proper mask with N95 filters when you're around other people.
• To prevent infection, make sure to wash your hands often with soap and water for at least 20 seconds, especially after using the bathroom. Check out these tips on how to properly wash your hands. Always carry alcohol-based hand sanitizer with you so that you can sanitize your hands when on public transportation or at restaurants. 
• Get tested: If you think you have COVID, it’s best to get a COVID test conducted, even if it’s an at-home rapid COVID test such as the FlowflexTM COVID-19 Rapid Antigen Test.

Remember that COVID vaccines and booster shots are now available to prevent the spread of COVID-19. Although no vaccine comes with a 100% guarantee to protect you from getting the virus, the vaccine indeed reduces the impact of the virus and boosts your chance of being immune to it.

The Bottom Line

Each different type of COVID test has its own pros and cons. Being armed with the above information helps you figure out which type of test is best for you. If you need rapid results, for example the PCR test might not be your best bet. 

Implementing safety precautions (such as regularly testing your COVID status) is important, especially since we all want this pandemic to be over. Since COVID often has no symptoms, this makes COVID tests even more important to conduct.

Explore the variety of reliable COVID-19 testing solutions from Project Screen, and get at-home COVID tests to use at your convenience, or pre-departure tests for your travels.