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How does PCR, Antibody, and Rapid Antigen Test Detects COVID-19 Infections?

Throughout the Covid-19 pandemic, the importance of trustworthy, easy to get testing for the disease has become increasingly important. Tests for Covid-19 are divided into PCR, antigen or antibody tests which use different samples to search for different hallmarks of the SARS-CoV-2 virus. Take a closer look at the different types of Covid-19 test.

What is PCR testing?

PCR tests use direct screening to detect the presence of viral RNA, which are evident in the body before any antibodies form. This means the tests tell whether or not somebody has the virus at a very early stage.

How does it work?

During Covid-19 pandemic PCR testing, elements known as DNA polymerase are added to a nasopharyngeal sample in labs. These substances make many copies of any viral RNA that are present. This is done to get enough RNA copies to signify a positive or negative result. Precisely planned primers and probes attach themselves to a series of genetic codes of the virus to signal that a pathogen has been found.

There is a 30% of chance of getting false negatives with different PCR tests. This means they’re useful for checking the presence of infection and giving almost clear results. This test also provides false-positive results.

What is a rapid antibody test?

Rapid antibody tests detect antibodies through a patient’s blood sample. These tests are mainly for mass analysis and reporting.

rapid antibody test

How does it work?

The antigen rapid test provides a simple swab test that senses specific proteins, also known as antigens, present on the surface of the Covid-19 virus and has 98.2% sensitivity in detecting viral levels that are currently considered to be infectious. The sample for this test is taken from a throat and nose swab, which is then tested by healthcare professionals, giving a result in less than 15 minutes.

The antigen test is the latest corona virus screening that senses proteins present on the surface of the Covid-19 virus. This is almost the same method as a PCR test – that is, by using nasal fluid on a swab. Antigen tests give quicker results than PCR tests and are not as expensive. In case the antigen test comes back negative, doctors can also recommend a PCR test for final reporting, depending on the condition and exposure of the patient.

What is antigen testing and how does it work?

Types of samples

Covid-19 Kit

Different tests require different types of samples. The most common sample types are:

Swab samples use a swab to collect a sample from the nose and throat. The types of sample includes:

  • Anterior nares – the sample is taken from just inside the nostrils.
  • Mid-turbinate – the sample is taken from further up inside the nose.
  • Nasopharyngeal– samples are taken from deep inside the nose and reaching the back of the throat.
  • Oropharyngeal – the sample is taken from the middle part of the throat, just beyond the mouth.

Saliva samples are collected by spitting in a tube rather than using a nose or throat swab.

Understanding your test results

  • Usually, in diagnostic tests, a negative report means the test did not sense the SARS-CoV-2 virus and a positive report means the test did sense the SARS-CoV-2 virus, and you are possibly suffering from Covid-19.
  • However, no test is 100% accurate. There is always a chance that your test will give a false result. For many tests, a false negative result means you don’t have Covid-19, but you may be infected, and a false positive result means you do have Covid-19 but you may not be infected.
  • If you get a negative result, you should keep performing preventive measures, like social distancing, washing hands and wearing masks, to decrease the risk of spreading Covid-19.
  • If you are sick, stay indoors and self-isolate away from others, even if you get a negative test result. Talk with your doctor to check if you should get tested again and advice on managing your symptoms.

The important thing you should know about coronavirus tests 

PCR and antigen tests are the most common, but they work differently

While antigen tests are done look for proteins on the surface of the virus to find the presence of the pathogen, PCR tests are done to seek genetic material, called RNA, which instructs the virus to produce these proteins.