Rapid testing in the way forward3 Dec 2021 08:58
https://twitter.com/pk_wendall/status/1466689449992110082?s=20
"When the goal is limiting transmission, timing of tests is everything. If you wait days for positive results before isolating, the time spent waiting must be factored in to the “effectiveness sensitivity” of a test. Time is always ignored as a test metric. This is wrong.
If people are infectious for 6 days and you have to wait 2 days for results, then for every 3 positive people detected, you miss the equivalent of an entire infection because the sensitivity while waiting is 0%. This means the “effective sensitivity” cannot break 67%.
What’s particularly bad but also ignored is the "0% sensitivity" while awaiting a lab PCR result is for everyone - even people who are at absolute peak virus and immediate isolation is most important. For these people, rapid tests detect >95% - with immediate action.
Continued failure of public health efforts and regulatory agencies to recognise time (& frequency) as metrics that are actually MORE important than molecular sensitivity for tests used to limit transmission speaks to our abysmal ability to focus on public health in a pandemic.
If we look back in time to 2020, our US FDA preferred and prioritized PCR tests with a 7-10 day turnaround over tests with a 15 minute turnaround. This meant that almost 100% of the tests used for most of 2020 had effectively 0% sensitive for infectious levels of virus.
To translate: FDA prioritized Lab tests that would identify near 0% of ppl in time to stop transmission over rapid tests that identify >90% of people in time to stop transmission. One of the greatest failures of thinking by our agencies responsible for 100,000’s of deaths."
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