Rapid Covid-19 tests are being deployed by the millions across the nation. The federal government is sending these tests, which can provide results in minutes, to states for educators, students, nursing home patients, first responders, and other sites. That’s a good thing. But in a rush to get individual test results, we’re making a dangerous public health mistake: We’re losing critical data about Covid-19.
For months, the U.S. has struggled to get accurate information about Covid-19 cases and testing about different demographic groups. As rapid tests surge — and are performed at sites that don’t follow specific Covid-19 data reporting processes — even more information will be lost.
Hundreds of Finlanders aged 75-80 were given a battery of physical and cognitive tests 30 years ago. The same tests were recently repeated, in 2017-2018, with Finlanders aged 75-80. The modern group showed substantial differences:
walking speeds .2-.4 meters per second faster
grip strengths 5%-25% stronger
knee extension strengths 20%-47% higher
better verbal fluency, reasoning, and working memory
This means that the modern group moves and thinks “younger.” “Performance measurements reflect one’s functional age,” says lead author Taina Rantanen, professor of gerontology and public health at the University of Jyväskylä.
I would not extrapolate the older age study findings to the general population. Clearly there are cultural, societal, dietary, climate and other differences in Finland that do not exist elsewhere. But at my age I’ll take good news about getting older anywhere I can find it.
Finland is different. They developed a real interesting rapid Covid-19 test.
Four Covid-19 sniffer dogs have begun work at Helsinki airport in a state-funded pilot scheme that Finnish researchers hope will provide a cheap, fast and effective alternative method of testing people for the virus.
Here’s the key: What is more important than a perfect test is one that turns positive during the time period in which an individual can spread the virus to others—and that’s, purportedly, what these cheap tests do well. Generally, disease transmission in COVID-19 is believed to begin early—several days before one becomes symptomatic. Viral load levels peak early and then they gradually decline, with an individual unlikely to be infectious approximately eight to 10 days after showing symptoms.
Though efficacy needs to be better proven, these antigen tests are efficient at detecting virus at high viral loads. When they are used frequently during this period of infectivity, Mina believes their sensitivity and performance would far exceed that of a single PCR test. At any rate, Mina and his colleagues have demonstrated in their statistical models thatpublic health surveillance depends much more on frequency of testing and rapid reporting of results than it does on the comparative sensitivity of the tests themselves.
Comparing PCR testing, the nasal swab vs. antigen testing which is much less expensive and produces rapid results, these tests are both commonly offered in Oklahoma. The difference in the tests is the sensitivity in the tests. The big difference between PCR and antigen is overall antigen tests are less sensitive. You can have confidence in a rapid antigen test if it says you are positive, but let’s say you are symptomatic and you go in for a test because you think you may have COVID-19 and they do an antigen test and you get a negative test — you should remember that 20% or more of antigen tests come back as negative. So there is high predictive value for positive.
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