At a glance
Also known as
Why get tested?
Testing for COVID-19 occurs in in a number of situations.
- The first goal is diagnostic testing in people with symptoms. The question asked here is: are symptoms due to COVID-19 or something else such as the common cold or flu? This is the most important question because COVID-19 is highly infectious and infected people need to be isolated as soon as possible to prevent them transferring the infection to other people – this is called community transfer. If you have any of the symptoms such as fever, cough, tiredness or loss of taste or smell, you must get tested
- A second reason to test is if you have been identified as being in a location close to someone who has COVID-19 – this will often be part of the Test and Trace process that the public health authorities may use to limit the spread of infection. In this situation, you may not yet have symptoms and you may be at the start of the infection process, but it remains important to test and see whether you are infected.
- You may also be tested in quarantine following COVID-19 diagnosis. These tests are conducted before you can leave, as it is necessary to confirm that you are no longer infectious. If you test negative, you can return to the community.
- Testing may be required to ensure that you are not infectious prior to international travel.
- Regular testing may be part of your employment requirements if you work on the front line in an area of higher risk, or with people who are vulnerable such as aged care, hospitals, or quarantine services.
The above testing principles may not be applied in all Australian States because of differences in how the pandemic has developed and managed in the different jurisdictions. To see what applies in your own State, check the information on the websites provided at the end of this article.
- Nose (nasopharyngeal) swab.
This is the most common way of being tested. A swab is carefully inserted into your nose (both sides) to pick up samples of mucus.
- Throat (oropharyngeal) swab
The swab will take samples from around the tonsils and the back of your throat.
A nose and throat swab are often combined.
These swabs will be placed in a tube and sent to the lab for testing.
Test preparation needed?
What is being tested?
Testing for COVID-19 can be done by two methods – Nucleic Acid Test or Rapid Antigen Test
- Nucleic Acid Tests
Nucleic acids in the COVID-19 virus are detected using a PCR (polymerase chain reaction) test. This method detects the genetic material of the virus and is the most accurate method available. It is a sophisticated test that involves several complex processes. The testing process is repeated as many as 45 times (cycles) per sample.
If the virus is present it shows up as a fluorescence signal. The fewer number of cycles required to detect the virus indicates a greater amount of virus (viral load) is present. If fluorescence does not appear until the final cycles, it suggests that the person has a low viral load – and they may have only recently been infected or were infected at some time in the past and are not carrying much virus. This can help in assessing how infectious someone is and when they became infected.
Due to the complex nature of the testing it may take 6-48 hours before you receive your result.
- Rapid Antigen Tests
These tests detect parts of the proteins on the surface of the virus called antigens. The test involves applying the material collected on the swab sample from the nose or throat to a small opening on the test strip. After a short time, a control band is displayed to show that the test kit is working and if the virus is present a second coloured band will appear.
RAT tests are far less sensitive than PCR-based testing and may not become positive until day 5 of symptoms or later. They are most accurate when the viral load is highest and when a person is likely to be most infectious. If the test is taken too early or too late in the course of infection, it may not detect the virus. The accuracy of the test can be increased by performing rapid antigen tests on successive days.
These tests have become more useful as the number of COVID-19 cases in the community increased so that they are now widely used especially in workplaces, Aged Care facilities as well as in the home.
What does the test result mean?
Results for PCR testing are usually available between 6 and 48 hours after sample collection and they are presented as being negative or positive for COVID-19.
A positive test means it is extremely likely that you have COVID-19. There are circumstances when a false positive result may be generated, but these are very uncommon.
If you have a negative result, you probably don’t have COVID-19 at the time your sample was collected. However, you can still be infected but not have enough of the virus in your nose and throat to show up. This may mean you are at the start or the end of an infection. Bear in mind that the test can only measure the virus that you have in your body at the time the test is taken. You could become infected immediately afterwards. Therefore, it is important to be tested at any time you have symptoms.
Modern medical tests are highly sophisticated, but they cannot be 100% reliable. There is always a small chance that someone may test positive for an infection they don’t have (false positive) or have an infection that goes undetected by the testing process (false negative). Sample collection plays an important role. The test cannot give an accurate result if the sample collection has not picked up enough virus particles.