Rapid antigen tests should be used only for symptomatic COVID-19 patients, close contacts and those with history of exposure, in outbreaks and in areas without access to RT-PCR confirmatory testing, HTAC emphasizes in a recent recommendation.


Rapid antigen tests and RT-PCR: Key differences

Rapid antigen tests for COVID-19 are used to detect antigens or viral proteins in the body which cause an immune response and imply the presence of viral infection. 

On the other hand, real-time reverse transcription-polymerase chain reaction (RT-PCR) test kits for COVID-19 detect genetic material. RT-PCR thus remains the standard test for diagnosis as it more accurately determines the presence of coronavirus and if a person is currently infected.


Rapid antigen tests and clinical management

Recent evidence shows that rapid antigen tests may be used for contact tracing, surveillance, and clinical management of patients with COVID symptoms. Because of this, the Health Technology Assessment Council (HTAC) currently recommends the test strictly for these specific purposes. 

Such cases include targeted screening and diagnosis of individuals who have symptoms of COVID or individuals who live in the same household as COVID patients. 

Similarly, the test may be used in grouping patients together in hospitals where it is important to enforce infection prevention and control measures and minimize disease transmission.

The HTAC also recommends the use of rapid antigen tests for suspected outbreaks of COVID-19 in isolated areas with no laboratories and immediate supply of RT-PCR test kits. 


Guidance for testing

The Council advises that individuals testing positive for COVID-19 using rapid antigen tests be isolated and managed as COVID-19 cases. 

As rapid antigen tests work best within five to seven days after a patient first experiences symptoms, the test should be conducted within this time period. Close contacts of positive individuals may be tested from four to 11 days after exposure even before symptoms develop. 

For symptomatic patients with negative rapid antigen test results, there should be confirmatory RT-PCR testing. Confirming those with negative antigen results using RT-PCR should be done within two days after the initial rapid antigen test. 

In areas with no access to RT-PCR confirmatory testing, asymptomatic persons with negative antigen test results but a high likelihood of exposure should complete the 14-day quarantine. 

Rapid antigen tests can also contribute to greater testing capacity provided they meet the technical specifications the HTAC recommends. However, more evidence is needed to establish its value in diagnosing asymptomatic individuals. The Council also recommends further exploring the value of repeat antigen testing compared to RT-PCR and symptom-based screening.


Read the Evidence Summary: https://bit.ly/314mxSv 

Read the Rapid Review: https://bit.ly/3755MKP