The national strategy for Covid testing determines that in situations of outbreaks in schools, OAP homes or other institutions rapid tests should be used so that ‘adequate measures’ can be brought in to help stem transmission as quickly as possible. Said health director Graça Freitas on Monday, these ‘antigen’ tests should be able to give results in less than 12 hours. They may not be as accurate as PCR tests more commonly used, however.
Explains a US public health report: “Antigen tests are less sensitive than molecular tests, meaning there may be false negative results.
“Negative tests should be treated as presumptive. If a healthcare provider is concerned that the person has COVID-19, even after a negative antigen test, then the test result should be confirmed with molecular testing”.
There are basically three types of tests available for COVID-19: molecular, antigen, and antibody (serology) testing. Molecular and antigen tests detect whether a person is currently infected, and serology detects whether a person had an infection in the past.
Molecular tests look for pieces of SARS-CoV-2, the virus that causes COVID-19, in the nose, throat, or other areas in the respiratory tract to determine if the person has an active infection, while antigen tests look for pieces of proteins that make up the SARSCoV-2 virus.
