A number of companies are offering COVID-19 rapid antigen testing. Whilst these tests are appealing due to a short assay time, from sampling to result, their use is currently not recommended in NSW. There are several reasons why their use is discouraged, such as operator challenges, results recording, transcription problems, and sensitivity issues. All of these are challenges with our current low rates of transmission in the community.
Are all tests the same?
Most people in NSW are familiar with the nose and throat swabs that are tested for genetic material from the SARS CoV-2 virus (the virus that causes COVID-19). These tests are the gold standard test for diagnosing COVID-19. The test used is called a Real Time/Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) which detects the presence of genetic material of the SARS-CoV-2 virus in a respiratory tract sample. This tells us if SARS-CoV-2 is present and thus who may have the disease COVID-19. Currently, RT-PCR is widely available in Australia. The time entailed in test performance, once the sample is presented to the RT-PCR device, is usually around six hours, but this does not include the extensive contribution that transport, pre-analytic preparation and data entry, for instance, may add to the overall turnaround time.
Rapid Antigen Tests
Rapid Antigen Tests have been used by some private industries, to give an indicative test for COVID-19 in their asymptomatic employees. This is not currently considered an appropriate and confirmatory test for a symptomatic person. The results for rapid antigen tests are usually available within 15-30 minutes and be conducted at the point of service i.e. at the workplace. A significant number of antigen tests for SARS-CoV-2 infection are being marketed domestically and internationally. These tests can be a problem in a low-prevalence country like Australia. The low prevalence of community COVID-19 in Australia means that the vast majority of positive test results with these devices will be false positive and will incorrectly ascribe infection in non-infected patients. It is also the case that small numbers of truly positive patients will record a false negative result with these tests and will thus be incorrectly considered non-infected. In a population which is not immune the detection of the very small numbers of truly infected patients is critical to control the distribution of disease within the community. So, a highly sensitive test is critical in a community with low prevalence of disease. Rapid Antigen Tests are not as reliable as RT-PCR and can miss people with COVID-19.
In NSW, whilst we have no or low community transmission, these tests are unlikely to add additional protection to a work environment. Good education of the workforce (not coming to work if unwell, isolating if they have been instructed to by NSW Health) and, where necessary, verbal screening of people attending a workplace are likely to provide adequate protection for most workplaces.
Any person presenting with respiratory symptoms consistent with COVID-19 infection should not be allowed to enter the workplace and should be referred for standard testing at one of the many testing clinics in NSW. They should isolate until they receive a negative result.
Users should only conduct rapid antigen tests under public health direction and with medical oversight, in strict accordance with the manufacturers' instructions.