The IP Lead needs to understand the importance of Rapid Antigen Tests (RATs) in detecting and managing COVID-19 and knowing when and how to collect a sample in order to inform residents and employees.

What is it? 

A Rapid antigen test (RAT) is a diagnostic tool widely used to detect the presence of COVID-19 antigens. It is a non-invasive, quick, cost-effective method of detection that plays a significant role in safeguarding resident and employee health by promptly identifying COVID-19 infection to manage this infectious disease effectively. The procedure involves collecting a nasal swab and analysing it for the presence of COVID-19 antigens.  

RAT Advantages 

Speedy Results: RATs produce results within 15-30 minutes, allowing for immediate decision-making and timely implementation of necessary measures. This is particularly valuable in controlling the spread of COVID-19. Unlike molecular tests like PCR (polymerase chain reaction), RATs do not require complex laboratory infrastructure or extensive processing time. 

Cost-Effectiveness: RATs are generally less expensive than molecular tests, making them a viable option for widespread testing, reaching more people and identifying infections promptly. COVID-19 RATs are currently available free of charge. 

Point-of-Care Testing: RATs are designed to be performed at the point of care, such as aged care facilities, and this allows healthcare professionals to administer and interpret the results without relying on centralised laboratories. This approach facilitates rapid screening and enables immediate intervention, reducing the potential for disease transmission. 

Early Detection of Highly Infectious Diseases: RATs are particularly effective in identifying diseases with a high viral load during the early stages of infection. They excel at detecting individuals who are most likely to transmit the disease to others, which is crucial for implementing isolation measures and breaking the chain of transmission. 

Limitations of RAT Testing  

Sensitivity and Specificity: RATs have lower sensitivity and specificity compared to molecular tests like PCR, so false-negative results are more likely with RATs because they may not detect low levels of antigens during the early stages of infection, e.g., 1 in 4 tests on people symptomatic for COVID-19 return a false negative; it can take 3-4 days after symptoms start for a RAT to be positive. Confirmatory testing with more sensitive methods may be necessary in symptomatic cases. 

Targeted Pathogens: RATs are designed to detect specific antigens associated with a particular pathogen, so they are not suitable for detecting multiple diseases simultaneously.  

Confirmation of Results: Positive RAT results may require further confirmation with a molecular test to rule out false positives. This additional step ensures accurate diagnosis and prevents inappropriate management decisions, e.g., prescribing the wrong antiviral. 

When to test?

A RAT should be carried out whenever a resident or employee shows symptoms of COVID-19, this is to identify and manage the infection appropriately.  There is no need to ask employees to do a RAT before returning to work if they are asymptomatic, evidence suggests that the RAT could be positive, but the person is unlikely to be infectious after seven days. 

NB: While COVID-19 RATs are well-known and widely used, the TGA (Australia) has approved two nasal combination self-tests (for use at home) that detect COVID-19 and influenza viral infections in humans; these are not government funded. Work is ongoing to approve a triple RAT which would include a test for RSV.