Diagnostic testing for COVID-19 infection is a key element in the strategy for limiting its spread. In an early release article in Australian Prescriber, microbiologist and infectious diseases physicians Drs Anna Brischetto and Jenny Robson explain what the different tests are, when they should be used, what samples should be collected and how to interpret test results.
“For health professionals, choosing which test to use to diagnose COVID-19 disease will depend on the clinical presentation and the stage of the illness,” says Dr Brischetto.
“Nucleic acid assays using swabs from the nose and throat are the cornerstone of diagnosing acute COVID-19,” she says.
“Depending on the logistics of collecting and processing the samples, the results of these tests usually take around 24-48 hours.
“There are also ‘point-of-care’ nucleic acid tests that use the same type of swabs as laboratory-based tests, but results come back in 45 minutes. However there is limited availability of these tests in Australia, and they are not suitable for testing large numbers of samples at the same time.
“Serological testing detects antibody responses to SARS-CoV-2 in the blood. These tests are used to detect past infection. Antibody responses can typically only be seen around 14 days after infection so are not used to diagnose acute COVID-19.
“Antigen testing detects acute infection in respiratory samples. While these tests are fast and have the potential to be carried out on large scale, they are not as sensitive as the nucleic acid tests,” she says. “The role of this type of testing in Australia is currently being evaluated.”
COVID-19 testing is a rapidly changing area and guidelines are evolving over time.
Read the full article in Australian Prescriber.