Notes

Questions

• Why does Australia not use more rapid antigen tests?
• Why only under the supervision of health professionals?
• Where else are they used in the world?
• When were they approved (for health use) in Australia? Rest of world?
• When were they approved for non-expert use?
• Why is TGA reluctant to approve things? Can approval be recalled (surely yes..)
• What other (non-COVID) tests can be used at home?
• Is supervision required every time? Can it be taught?
• Would a video/instructions be sufficient?
• How accurate is "inaccurate"? How to reliably compare?
• How often is testing needed for wide-scale screening?
• How much to tests cost? Is that total cost (healthcare worker and logistics)? What could be cheaper
• Does test cost affect accuracy?
• How is accuracy determined?
• How accurate are PCR tests?
• Accuracy/time trade-off
• Are asymptomatic / low symptom cases common enough to cause outbreaks?
• Could rapid antigen tests be used to prevent them?
• What are possible use cases? i.e. ticketed events while in line, or as a quick detection for supermarket outbreaks?
• Should they be used for daily areas (ie schools, in-person workplaces)? How often?
• Are low symptom people counted as "asymptomatic"? Or if you cough once it's considered a symptom?
• Is being symptomatic based on self-reporting or observation?
• Are vaccinated people more likely to be asymptomatic?
• Are vaccinated people less likely to suspect they have covid? Assume it's something else?
• How do antigen tests work?
• What are the actual risks? False positive (one person isolates) seems relatively low cost. False negative still better than current rate
• who supplies current PCR tests? Is there vested interest in preferring those than antigen?

From ABC

The TGA argues that for now it is critical tests are supervised.

Primarily, it wants to ensure positive tests are immediately reported to health authorities. Given the current low, or zero, transmission in large parts of the country, every positive test is very significant.

It also notes the importance of tests being administered and interpreted correctly too.

This seems absurd to me. Ignoring non-compliant people (who are unlikely to get PCR tested anyway!), you are missing out of tests for aymptomatic and low-symptom people. The "just got a bitofa cough" crowd might not want to commit to a long wait in a queue, but we willing to for the lower barrier to a quick at-home test.

Every positive test is indeed very significant, but so is every positive case! The lower detection rate in asymptomatic people (apparently ~60% accuracy) is still much higher than what we currently get - potentially closer to 0%, since we tell people to get tested only when they have symptoms or have visited an exposure site.

At-home and non-professional test

Current reasons given for not rolling out:

• low accuracy
• needs trained staff
• poor documentation
• illegal in 2 states to home administer
• not trusting people to do the right thing after testing positive

At least several of these are nonsense.

Currently Australia requires health professional to at least observe the test. This can be in person or over video. What do they need to observe? Could they teach once and then verify, then the other person is allowed to do it themselves next time? I assume this is how it works for diabetics.

I assume the main risk is contamination/dilution of the sample, leading to a false negative (you have it, test doesn't tell you). Should confirm if this is actually the concern, haven't seen actual explicit risks listed other than variations of people not being professional.

Antigen test accuracy

Notes from COVID-19 Critical Intelligence Unit: Rapid antigen testing has some good references. In particular "Issues with false positive and false negative test can be addressed by repeat testing".

Antigen Testing Every 3 Days Is Highly Sensitive for SARS-CoV-2

However, antigen testing’s sensitivity reached 98% when conducted at least every 3 days, bringing it on par with PCR testing at the same frequency.

Only needed twice a week!

Asymptomatic spread

According to a systematic review and meta-analysis from December 2020 (via RACGP), the number of asymptomatic people is lower (<20%) and "it also found transmission rates are lower by about 42% for asymptomatic cases when compared with symptomatic cases".

An article in Nature says that behaviour (proximity when talking, mask adherance etc) and environment (indoor, poorly ventilated) are more significant to rate of infection than viral load.

And CDC says fully vaccinated people can still infect others.

Asymptomatic screening with low case rates

Is screening of the entire population

Even from predictions last year about asymptomatic case rates being higher (NB this was pre-Delta), an argument against screening asymptomatic people was relatively low case rates in Australia. This is still basically the case (primary close contacts of known cases is <1% of total population), but still is tens of thousands of people in isolation.

Vaccination and reduced symptoms

Are vaccinated people more likely to be asymptomatic?
They are known to still spread virus (Delta at least), so should still be testing! There is the reduction in hospitalisations, but if it can still be spread among the vaccinated population surely rapid testing is a more viable strategy?!

TGA approval rate

From a Tyler link on our anti-science science advisors, yet again (this was on boosters, sentiment is the same):

they refuse to apply scientific reasoning under the heading of expected value theory