Utah ranked ninth out of 50 states over the weekend, due to the high percentage of tests that tested positive.
(Trent Nelson | The Salt Lake Tribune) Kylie Archuleta and Joshua Brimhall conduct the COVID-19 test at the University of Utah Health’s Farmington Health Center on Friday, July 31, 2020.
One of the most observed – and often most alarming – data from the COVID-19 pandemic is the test’s positive rate.
It is a simple metric: of all processed COVID-19 tests, how many of them tested positive?
But Utah’s real rate – which reached 32.2% on Monday – is more complicated to calculate, as some amateur data analysts have discovered.
For example, the Utah Department of Health reported on Sunday that the seven-day continuous average for the test’s positive rate was 29.7%. (Public health officials use seven-day averages for many metrics, because they reveal general trends rather than the larger up and down swings in daily reports, leveling out factors such as weekends and holidays.)
But if you take the number of positive cases during the previous seven days – 18,599 – and divide by the total number of tests processed, which was 52,576 for the seven days ending on Sunday, you will get a value of 35.4%.
David Nierenberg, an airplane pilot who lives in Salt Lake City, found similar discrepancies when examining the UDOH figures last week.
“The last few days of positivity percentage reports have been canceled,” wrote Nierenberg to The Salt Lake Tribune last week. “Could you post the actual number tested during the past week in the next article to correct the record?”
So why is the state’s official positivity rate different and lower? With the daily figures released by UDOH, “you don’t have all negative results accounted for,” explained Tom Hudachko, a department spokesman.
Positive test results are reported faster than negative ones, so UDOH sets a time frame – usually around five days – for negative results to be achieved, Hudachko said. Without this lag, the rate of positivity would be artificially high, he said.
A positivity rate of around 30% is already alarmingly high. Public health experts say such a high positivity rate is an indicator that many people have the virus and are not getting tested.
Dr. Todd Vento, an infectious disease physician at Intermountain Healthcare, noted on Monday that Utah ranked ninth out of 50 states this weekend for its test positivity rate.
“We still have a very positive broadcast,” said Vento at an online news conference on Monday.
“Testing is important, but that’s not how you get out of a pandemic. You don’t test to get out of a pandemic, ”warned Vento. “You prevent and prevent the spread of disease. That’s how you get out of a pandemic. “
Government officials, said Vento, “fell into this trap from the start” that “we just have to test more to show that we have more negative results [tests]. This is really the wrong approach. The right approach is that we have to test harder to find out the truth. “
UDOH targets a 5% test positivity rate, Hudachko said. That low rate, said Vento, “would show excellent control” of the spread of the virus. “We haven’t been 5% for months and months, nor have many states in the United States,” said Vento.
The way to lower the test’s positivity rate, said Vento, is to vaccinate people and, until that happens, to continue doing what health experts have been saying for months: “You have to wear a mask, 100% of the time when go out in public and in contact with other people. You have to stop gathering, and [you have to be] maintaining your physical distance. “
Vento added: “The message is not going to change because the calendar year has changed. The message is the same. “
This story is developing and will be updated.