As Hong Kong is fighting its fifth wave, mass Covid-19 testing represents an essential strategy to understand the spreading of the new variant and curb the number of infections. 

Currently, there are two major types of testing options to diagnose SARS-CoV-2 infections: Rapid Antigen Tests (RAT) and Polymerase-Chain Reaction (PCR) – or molecular- tests. 

While the two tests work in different ways, they can both be useful in helping you detect an infection early, find suitable medical care, avoid complications, and reduce the risk of transmitting the virus to those around you. 

At the same time, over the past two years, people around the world had to quickly become familiar with terms such as “quarantine”, “incubation period”, and “asymptomatic”. So, if you feel unsure about what these two tests are and what they are useful for, you are not alone. 

Find out all you need to know in this guide by Trinity Medical.  

What Are PCR Tests?

Reverse Transcription Polymerase Chain Reaction (RT-PCR) tests – also commonly known as molecular tests – represent the most reliable and accurate Covid-19 tests currently in circulation. 

According to recent studies, they offer an accuracy between 98.7% and 99.5%, depending on whether the subject is symptomatic or asymptomatic, and how long the infection has been present. 

PCR tests are commonly performed in specific clinics, but qualified healthcare providers can also take your genetic sample at home, in a hospital, or at a drive-in point. The samples are then sent to a lab for analysis, and you will receive your results within 24-48 hours.  

How Do PCR Tests Work?

Both antigen and PCR tests are effective in their own way, but they work in different ways. In the case of PCR tests, the healthcare provider will collect a genetic sample from your nose, which contains both your DNA and the DNA of the virus. 

The sample is then brought to a lab, where it is isolated from the swab and inserted in a thermocycler – a special machine that causes the sample to undergo 30-40 heating and cooling cycles. This process, also known as a polymerase chain reaction, causes the sample to multiply and create billions of copies, thus making it easier to identify the presence of the SARS-CoV-2 virus. 

Thanks to specifically-designed software, the lab scientists will then be able to read and interpret the results.

When To Use a PCR Test

Since PCR tests require the use of specific machinery and dedicated laboratories, they cost more than antigen tests, and it can take multiple days (at peak times) to receive your results. 

However, you should consider this test if you:

  • Have symptoms that can be associated with a Covid-19 infection, such as a persistent cough, runny nose, congestion, fatigue, headache, and a sore throat
  • You don’t have symptoms, but you believe to have been in contact with an active Covid-19 case
  • You need to travel and present a negative PCR test result as part of a country’s entry requirements 

What Are Rapid Antigen Tests?

While PCR tests are considered to be the “gold standard” of Covid-19 tests, Rapid Antigen Tests (RAT) have their benefits. Firstly, RATs offer results within 15-30 minutes and come at reduced costs. 

Additionally, they can be performed by healthcare providers at a clinic or doctor’s office, but they can also be carried out at home by yourself or other people without professional training. 

To understand the unique advantage of RATs, it is important to be clear that all Covid-19 tests will tell you whether you have an active SARS-CoV-2 infection or not at the time of the test. This means that you can be infected immediately after, and they don’t provide protection against infection. 

So, while PCR tests can be extremely accurate, rapid antigen tests allow for more frequent testing, thus playing a vital role in helping curb the spread of the virus

At the same time, RATs are less accurate than PCR tests and are around 72%-58% (depending on whether you have symptoms) efficient in detecting the presence of SARS-CoV-2.

How Do Rapid Antigen Tests Work?

Antigen tests work differently compared to PCR tests, and they don’t amplify the genetic sample collected. RATs are performed by collecting a sample of your mucus, saliva, or tissue through a long, thin, and flexible swap. 

The sample is then inserted in a “buffer solution” that breaks apart the particles. The solution is then added onto a test strip that has lab-made Covid-19 antibodies present on two lines. As the solution spreads over the test strip, the antibodies will search for antigens in the sample. If they find them, they will trigger a reaction, causing the “test” line to become colored. 

Since the sample is not amplified through the PCR reaction, you will need to have enough viral antigen in the sample for the antibodies to react. Therefore, if you are at the early stages of your infection or you are asymptomatic, the test might not be able to detect the infection. 

When Do You Need a Rapid Antigen Test?

If you have symptoms similar to the ones caused by a Covid-19 infection, a rapid antigen test is the first point of call to check whether you are positive for it or not. Rapid antigen tests can be used often, for example before going to work, attending an event, or visiting family. While they are not the most accurate types of tests, they can still reduce the chances of infection. And, you’ll be able to receive your results within 15-30 minutes of undergoing a test. 

Book Your COVID-19 Test at Trinity Medical

Covid-19 tests don’t replace the efficacy of vaccinations and social-distancing best practices in helping curb the spreading of the virus. However, they can make you aware of an infection, seek treatment early, and avoid transmitting it to your loved ones. Whether you need a PCR or antigen test, Trinity Medical can help you find answers faster. Book your test today.  

What’s the Difference Between a PCR and Antigen Test?