At a glance

Also known as

Coronavirus

Why get tested?
Testing for SARS-CoV-2 occurs in in a number of situations.
  1. The first goal is diagnostic testing in people with symptoms. The question being 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 that can occur with a COVID-19 infection,  you must get tested.
  2. 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 in all states and territories 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.
  3. Another situation is when you have been placed in quarantine following COVID-19 diagnosis.  You will routinely be tested for COVID-19 on day 2, day 7 and day 12 of the quarantine period, or at any time you first experience symptoms of COVID 19. Tests are conducted before you can leave, it is necessary to confirm that you are no longer infectious. If you test negative, you can return to the community.
  4. Testing may be required to ensure that you are not infectious prior to international travel.
  5. 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, hospital or quarantine services.
Test preparation needed?
Sample

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
This will take samples from around the tonsils and the back of your throat.
These swabs will be placed in a tube and sent to the lab for testing.
 
Any preparation?
None required
 

The Test

What does the test result mean?

Results are usually available between 24 to 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 is given, but these are very uncommon. 
If you have a negative result, you probably don’t have COVID-19 at the time you took the test.  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.  This is why it is important to be tested at any time you have symptoms.

Modern medical tests are highly sophisticated, but they cannot be 100% reliable. Test designers must balance many competing requirements. 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 has not picked up enough of the virus.
 

Is there anything else I should know?

  • The overwhelming majority of COVID-19 tests are conducted in laboratories using a process called the polymerase chain reaction (PCR). This looks for the genetic material of the virus and is the most accurate method to detect it. This is a sophisticated test that involves a number of complex processes.  The testing process is repeated as many as 45 times (cycles).  The virus shows up as a fluorescence.  The earlier the virus shows up in the cycles the greater the amount of virus (viral load). If fluorescence does not appear until the final cycles, it suggests that the person has a low viral load – possibly, they have been only recently 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.   Specially trained scientists are required to oversee the test and interpret results.
  • Other tests for COVID-19 are available but not yet used widely. These include more rapid PCR tests which are also accurate but are being used in some regional communities to generate results more quickly and shorten the time to diagnosis.
  • There are also antibody (serology) tests for COVID-19 which do not detect the COVID-19 virus but measure the body’s response to the virus by forming antibodies. Your body makes antibodies as a way of fending off infections. When you recover from a COVID-19 infection, your COVID-19 PCR test becomes negative for the virus, but your antibody test will be positive and be a measure of your immune response. Antibody tests are widely used to manage many infectious diseases.
  • There are also antigen tests for COVID-19 which detect bits of proteins on the surface of the virus called antigens.  The test involves applying the swab sample to a small opening on an oblong test strip and after a short waiting time. The virus is shown by the presence or absence of a coloured band. In Australia, these have not yet been approved for use for public testing in any state or territory. However, they are used by some private organisations and for research purposes.

Last Review Date: September 7, 2021


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