What You Need To Know About Rapid Antigen Tests (RATs)

Following the significant rise in COVID cases as a result of the movement away from elimination strategies and the strain on PCR testing, we have seen a rise in interest in Rapid Antigen Tests (RATs).

But what role do RATs play in workplace COVID-19 risk management and what are the considerations for their use?

Which Tests You Should Use

Only Australian Government Department of Health Therapeutic Goods Administration Rapid Antigen Tests should be used. See the list of approved tests.

The test units vary by their clinical sensitivity as well as the method of collection.

Clinical sensitivity categories for RATs ranges from 80- 95% PPA. Positive percent agreement (PPA) is the proportion of individuals that, during testing, produced a positive test result using a COVID-19 rapid antigen self-test, in comparison with a positive result that was obtained using a more sensitive laboratory PCR test.

The range of sensitivities are detailed in the table below.

Tests may use either:

• Oral fluid (saliva)
• Nasal swab

Which Days You Should Test On

RATs are most likely to produce a true positive result in the first 7 days of symptom onset when the viral load is highest. In the early and late stages of the virus, individuals may still be contagious but not test positive. In the case of a person in the potential early stages of infection a test should be repeated within 1-3 days.

Other Testing Considerations:

• Manufacturers of RATs highlight that these tests should be used in association with PCR testing to confirm the results
   
• Nasal swabs may not be as suitable for workers who suffer from nose bleeds or have had recent facial surgery. Saliva testing is likely also to be more comfortable and as such may see greater compliance with the test method
   
• The timeline for reading the test result is important with a delay of around 10-15 minutes to read the result and a maximum time beyond which the result is no longer valid
   
• The test methods will vary between makes and models and instructions for the specific test should be consulted
   
• Storage should typically be between 2 and 30 degrees (not stored in the freezer)
   
• The test units have a use by date and should be used as soon as they are opened
   
• Fake positives can be induced through the use of fruit juice or soft drink (and probably a range of other liquids) which are acidic  Read More
   
• Confirmed diagnosis of COVID-19 in the workplace requires notification to the regulator. With RATs being used as the only diagnostic tool a RAT positive result at the workplace should lead to a notification of the Regulator
   
• Positive RATs in Victoria are also required to be notified to the Department of Health
   
• If testing is conducted at a workplace, a suitable area should be provided along with cleaning materials, procedures, PPE and disposal means

Summary

• RATs are most useful to identify if a person with flu like symptoms has COVID-19 within 7 days of the symptoms commencing
   
• Ideally, tests of very high sensitivity should be utilised
   
• A negative result on a rapid antigen test is not conclusive evidence a person is not COVID – 19 positive and/or contagious with the disease
   
• RATs may form part of an overall response to reducing the risk of COVID-19 transmission within workplaces with other controls available from the hierarchy of control utilised to ensure the risk is reduced as far as reasonably practicable

Some General COVID-19 Controls In Accordance With The Hierarchy Of Control

Elimination

• Remote work
• Workforce bubbles

Substitution

• Conduct work outdoors

Engineering

• Ventilation
• Reduced surface contact through building modification (i.e. automated taps, doors )

Administration

• Vaccines and boosters
• Check-ins and declarations
• Temperature / pulse oximetry where appropriate
• Use of Rapid Antigen Tests
• Good general hygiene
• Cleaning

PPE

• Wear masks in poorly ventilated areas and in line with CHO directions.