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Coronavirus tests are being fast-tracked by the FDA, but it’s unclear how accurate they are


The dangers of inaccuracy

In the absence of data, physicians and public health officials are left to guess how many false negatives may be occurring – which could have serious consequences both for individuals and for combating the spread of the disease.

“You want to be right every time, because you miss somebody, and tell them that they’re negative, then you’re infecting people,” said Gutierrez, the former FDA official. “Let’s say you consider Amazon essential, and at the warehouse they’re testing people, even if they miss 1 or 5 people out of 100, that can be problematic.”

In addition, false negatives can make it more difficult to track spread of the virus, since those patients are not reported as confirmed cases and people who die without a positive test result won’t be counted in COVID-19 mortality statistics.

False positives also present problems. If you mistakenly think a patient has COVID-19, “then you have the potential to clog up the health care system and waste personal protective equipment and the time and effort of health care workers who think they are caring for individuals with COVID-19,” Stanford’s Pinsky said. “In addition, you’re producing a lot of anxiety for the patient.”

Pinsky says he hopes that real-world data will be gathered on the tests’ performance, especially as more and more come on the market: “If physicians have this information, they could move on to a different, better performing test and use that instead.”

Dr. Yukari Manabe, associate director of Global Health Research and Innovation at Johns Hopkins Medicine, estimates that 10%-25% of test results are false negatives. That’s not based on any data, she cautions, since hard evidence isn’t available. But she has been noticing many patients in the Hopkins system being tested more than once, when the first result doesn’t match their clinical symptoms.

Like others, Manabe acknowledges that the FDA has needed to greenlight tests quickly in order to get them out into the public. But she laments that companies weren’t encouraged to develop diagnostics earlier, which might have allowed the agency to keep the bar for approval higher, and also churn out more tests sooner.

“If people had seen the writing on the wall back in December, someone should’ve paid these companies what they needed to develop these tests on platforms that could’ve been rapidly ramped up to millions of tests,” Manabe said.

Instead, a test shortage caused doctors to limit tests to only the sickest patients, at a time when the virus had probably moved out of the back of the nasal cavity and into their lungs. A larger supply would have allowed for testing more people as soon as they started showing symptoms. That would have resulted in a lower rate of false negatives, Manabe said, since nose swabs are more likely to detect the virus soon after it’s been contracted.

The next wave of tests may be even less accurate

The questions swirling around the accuracy of the COVID-19 diagnostic tests are likely to persist as the next set of tests – antibody blood tests – start hitting the market. Already, the FDA has authorized the first of these tests, which search for molecules in a patient’s blood that can indicate if the immune system did battle with the coronavirus. Unlike the swab-based tests, which look for the viral RNA that indicate active infection, antibody tests are used to seek evidence of a past encounter with the virus.


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