Rapid virus tests: Speed over accuracy?

of people who took quick-result coronavirus tests at a Manchester, Vermont, clinic in July were told they had the virus, only to be informed days later that more accurate lab tests concluded they didn’t.

Last week, Quidel, the company that makes the rapid antigen test used by the clinic, stood by the original results. The top executive said it’s “highly likely” his company’s test was correct, and the state of Vermont’s conflicting lab-based test was “at risk of providing inaccurate results.”

As companies and universities create their own strategies to widely test employees and students – even those with no symptoms of COVID-19 or no known exposure to the virus – experts warn such confusion over conflicting results is inevitable.

Widespread testing can identify people who have the virus and halt the spread of some new cases. But because no test is infallible, some cases will be missed, and some people will be forced to miss work after false positives.

Ohio Gov. Mike DeWine said he tested positive on a rapid diagnostic to detect the COVID-19 virus before he was to greet President Donald Trump at a Cleveland airport. Two follow-up tests using a more precise, lab-based test showed the governor didn’t have the virus.

In Maine, 19 summer campers tested positive last month using a rapid antigen test, only to be cleared by the state’s lab test, the Bangor Daily News reported.

It’s a scenario that will “come up over and over again,” said Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security.

“We are going to blanket the country with tests,” said Nuzzo. “A lot of the push around testing has really been approached from a tech-forward perspective with a goal of trying to reopen our economy and not necessarily thinking through what the consequences are.”

Assistant Secretary for Health Brett Giroir said the USA should have up to 90 million tests in September – an average of about 3 million tests each day. As many as 40 million tests will be “point of care” tests with rapid results.

The Food and Drug Administration granted emergency use authorization to three rapid antigen test manufacturers to diagnose COVID-19: Quidel, LumiraDx and Becton, Dickinson.

The Trump administration invoked the Defense Production Act last week on federal contracts with Quidel and Becton to expedite production of antigen testing machines that can provide impret mediate results for 14,000 nursing homes. The effort “is our highest priority to save lives,” Giroir said.

The National Institutes of Health issues grants through a $1.5 billion “Shark Tank”-style competition called Rapid Acceleration of Diagnostics. The goal is to bring capacity up to 6 million daily tests by December.

Lab experts worry the push to test millions of Americans every day, without policies on how to use and interpret results, could confuse people who get conflicting answers.

PCR tests detect the virus’s genetic material. They find even low levels of the virus, so they have been the diagnostic test for public health and clinical labs since the beginning of the pandemic.

Antigen tests detect specific proteins on the surface of the virus. Testing materials are cheaper and more plentiful, and the tests are fast, delivering results in 15 minutes. They’re less sensitive than PCR tests and more likely to miss a case.

Because no test is always accurate, doctors who analyze test results must consider other factors, such as how widespread the virus is in a community. If someone tests positive but shows no symptoms, has no known exposure and lives in a community with relatively few cases, it’s difficult for a doctor to interDozens that result.

“The false negative and false positive rates for any test are never zero,” said Dr. Dwayne Breining, executive director of Northwell Labs.

Speed more vital than accuracy?

Some experts want the FDA to loosen oversight of rapid tests that can be taken at home and deliver immediate results, albeit without the sensitivity or accuracy of lab tests.

Michael Mina, an infectious disease epidemiologist at the Harvard T.H. Chan School of Public Health, said more inexpensive, at-home tests will be accurate enough to detect when somebody is infectious.

PCR testing can pick up signs of the virus even when somebody is no longer infectious, he said. That means some people are unnecessarily quarantined after they recovered.

“The travesty is that we’re spending so much time focusing on capturing people over here by mistake that we’re missing the people who are actually infected, and those are the people we really should be quarantining,” Mina said.

Others said the bigger challenge rests not with the technology but with deciding how to manage and interpret results that are not always correct.