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A New Worry Emerges on Coronavirus Tests

Newser — John Johnson

The good news: Coronavirus testing is expanding as both private labs and government institutions speed up the process. The bad news? The jarring possibility that 1 in 3 infected test subjects are getting false negatives.

The stat comes from a Wall Street Journal story in which doctors and health care experts assess the current testing climate. The caveat: "They caution that only limited data is available, and their estimates are based on their own experience in the absence of hard science." Coverage and related developments:

  • Not so great: An exec at the medical group Envision Healthcare tells the Journal that currently available tests have a "sensitivity" of 70%, a measurement of accuracy.

What this means is that "nearly one in three positive patients walks away with a reassuring negative result," writes Christopher Weaver. That is a worse mark than is typical for such tests, but the estimate seems legit, says a physician in Kentucky.

He and other doctors are learning this first-hand when patients who test negative return with worsening symptoms.

  • Why? A big reason for the low marks is the need to rush tests into service.

The FDA is trying to walk a fine line in relaxing requirements while assuring accuracy amid pressing demand. In normal circumstances, the CDC might take about a year to approve such tests, per the Journal.

An Ohio State doctor sums up: “The whole testing field is in flux. The thing that is different this time is most of these tests are going through a really rapid validation process.

As a result we can’t be completely confident in how they will perform.”

  • Another issue: The nation's first testing crisis was the lack of tests available.

Now that more are out there, the Atlantic sees a "new coronavirus-testing crisis" unfolding—staggering backlogs in getting results. This time, the federal government isn't the culprit.

Instead, it's the private companies "that now dominate the country's testing capacity," write Alexis Madrigal and Robinson Meyer. For example, Quest Diagnostics acknowledged it has been overwhelmed by demand in California, which is delaying results there longer than the typical four to five days.

  • Fast one: Abbott Laboratories began shipping rapid-response tests—they deliver results in a matter of minutes—around the country this week.

The company is working with the White House on the logisitics, but the Washington Post reports that a complicated debate is underway about a simple question: Where should they go? One camp thinks hot zones, but a competing camp thinks it's wiser to send them to areas with fewer cases, such as rural areas in the South.

It appears the latter camp has swayed VP Mike Pence, the argument being that authorities need "to figure out the spread in places where we don’t quite understand it now," as one official puts it to the Post.

  • Different approach: The FDA has just approved the first coronavirus test that looks for antibodies in the blood, rather than looking for the virus itself, reports the Verge.

Because it takes time for the body to produce antibodies, this type of test is more effective in determining who had the virus, rather than who has it.

But this can be valuable in helping determine who might have enough immunity (this is still a little iffy) to return to the public sphere, and it can give researchers a better sense of the virus' full spread.

The test, by Cellex, must be conducted in a lab. Results are ready in about 15 minutes.

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