False negatives in coronavirus tests ‘uncomfortably common,’ doctors say. Here’s why

If you test negative for coronavirus, does that mean you don’t have it? Not necessarily, some doctors say.

“False-negative test results — tests that indicate you are not infected, when you are — seem to be uncomfortably common,” Dr. Harlan M. Krumholz wrote in The New York Times.

A study conducted in China, which has not been peer-reviewed, suggests as many as 30 percent of negative coronavirus tests may be incorrect.

Those results seem to match what some health care experts in the United States are seeing, Bloomberg reports.

“Our infectious disease experts think that about 30 percent of patients we believe have covid are testing negative,” said Thomas Huth of Reid Health in Indiana, according to the publication. “We have tested some again, but they remain negative.”

More than 1.8 million cases of the COVID-19 virus have been confirmed worldwide with more than 112,000 deaths as of April 12, according to Johns Hopkins University. The United States has more than 530,000 confirmed cases with more than 20,000 deaths.

The World Health Organization has declared the COVID-19 virus a global pandemic. In the United States, President Donald Trump has declared a national emergency.

Some doctors no longer rely on coronavirus tests

“A negative test often does not mean the person does not have the disease, and test results need to be considered in the context of patient characteristics and exposure,” Dr. Priya Sampathkumar writes in a Mayo Clinic article on the problem.

“If a patient presents with classic covid symptoms, but tests negative, they’ve still got covid,” said Dr. Jeremy Sperling, chair of emergency medicine at Jacobi Medical Center in New York City, Bloomberg reports.

“There is just nothing else it could be in New York City in 2020,” Sperling said, according to the publication.

Why are false negatives so common in coronavirus tests?

There are several potential explanations.

For one, the nasal swab used to collect mucus to be tested in the lab can be tricky to perform, even for trained medical personnel, The New York Times reported. It’s invasive and patients often squirm.

“They’re not getting far enough back there to get a good sample,” said Ryan Stanton, an emergency medicine physician in Lexington, Kentucky, Bloomberg reported.

Once collected, specimens go to the lab for reverse transcriptase–polymerase chain reaction testing, which detects viruses in the genetic structure of cells, The New York Times reports.

But these kinds of tests are better at finding coronavirus than at confirming specimens are coronavirus-free, the Mayo Clinic reports.

Also, the federal Food and Drug Administration has loosened guidelines to get coronavirus tests on the market faster in response to the quickly spreading pandemic, Bloomberg reports.

In addition, scientists are still struggling to learn as much as possible about the COVID-19 virus.

Both factors mean hospitals and public health experts have little data to go on when analyzing test results, such as when it’s best to test patients for the virus, Bloomberg reported

Finally, dire shortages of test kits mean that it’s difficult for hospitals in some parts of the United States to conduct multiple tests on patients to confirm an initial negative result, according to the publication.

Why are false negative tests a problem?

Gerardo Hernandez, 39, tested negative for coronavirus despite persistent tiredness, coughing and fever, the Los Angeles Times reported. Now the Adelanto city leader in California’s Mojave Desert is in critical condition on a ventilator.

Tracy Hernandez said she believes the confusion and delays prevented doctors from trying experimental medicines that may have helped her husband, according to the publication.

“He is on life support ... that’s the scariest thing,” she said, the Los Angeles Times reported. “I never knew in my entire life I would have to say that about my husband, but he is literally fighting for his life right now.”

Along with the peril to individual patients, false negatives make it harder for public health officials to respond properly to the pandemic, the Mayo Clinic reports.

“Even with more testing, we are likely to be underestimating the spread of the virus,” Krumholz wrote in The New York Times. “For now, we should assume that anyone could be carrying the virus.”

This story was originally published April 12, 2020 at 10:17 AM with the headline "False negatives in coronavirus tests ‘uncomfortably common,’ doctors say. Here’s why."