A month after Connecticut officials reported at least 90 false-positive test results, the FDA issued a warning to health care providers using a specific testing kit. There has been a problem with false-positive coronavirus test results coming from the Thermo Fisher Scientific TaqPath COVID-19 Combo Kit. The FDA approved Emergency Use Authorization (EUA) for the kit in March.

The problem is with the testing kit itself, as well as with an outdated software system. The FDA released a warning to clinical laboratory staff and health care providers of the risk of false results. With updated instructions and updated software, the problem should be fixed according to the FDA.

The first issue is related to inadequate vortexing and centrifugation of RT-PCR reaction plates. Thermo Fisher Scientific’s conclusion from investigations of customer complaints indicate that inadequate vortexing or centrifugation can lead to false positive results. Thermo Fisher Scientific has updated these instructions to reduce the risk of inaccurate results. The updated instructions related to vortexing and centrifugation are important for both laboratories performing testing according to the authorized instructions for use and laboratories who are performing validated modifications outside of the authorization.

The second issue is related to the assay Internal Positive Control (IPC) and requires laboratory staff to upgrade their software to reduce the risk of invalid, potential false negatives, or inconclusive tests and to decrease the potential need to retest.

The FDA went on to issue some specific recommendations to health care workers to increase accuracy with the testing kits. The Thermo Fisher Scientific TaqPath COVID-19 Combo Kit received emergency authorization in March for use only in laboratories in the U.S. It is certified to perform moderate and high complexity tests. Between March and July, several modifications have been made through supplemental EUA requests. The test is designed to detect the virus that causes COVID-19 using upper respiratory specimens, like nasal swabs. The FDA encourages health care providers to report any adverse events or suspected adverse events experienced using the testing kits.

A month ago, Connecticut public health officials first reported that at least 90 people had received false-positive results for the coronavirus. Most of those receiving false-positive results were residents of nursing homes or assisted living facilities. It’s important that testing kits are updated and improved so that false-positive results don’t become more common. Lab tests are leaned upon as the backbone of U.S. screening for coronavirus. More than half of the roughly 750,000 tests developed daily in labs are for the coronavirus. This testing kit looks for traces of coronavirus genetic material in nasal swabs taken from patients. The FDA recommends that in order to avoid false results, labs consider retesting certain positive results and take preexisting conditions into mind with positive tests.

The test runs on a large, automated machine used in hospitals, government, and commercial labs to look for diseases such as HIV, hepatitis, and flu. The FDA has given its approval to more than 200 tests for the coronavirus since February. False-positive results are to be expected in at least a small percentage of false negatives, as well as false positives. Laboratories have continued to scramble to meet testing needs during the pandemic. With so many tests approved on an emergency basis, we should probably be surprised that more stories like this one aren’t being reported. Settings like nursing homes are ripe for incorrect results to be found in clusters. It stands to reason if 90 cases of incorrect results were found in Connecticut nursing homes and assisted living facilities, there may be a larger problem, a larger amount of false-positives being reported elsewhere.

Dr. Albert Ko of Yale’s School of Public Health said the potential accuracy problems have “pretty serious implications” given that Thermo Fisher’s test is used widely both in the U.S. and around the world to screen for coronavirus.

The FDA statement did not provide any details on how many test results may have been affected by the problem.

Shares of Thermo Fisher Scientific Inc. (tmo) were down 0.1% in premarket trading on Tuesday after the FDA released Monday’s statement. Thermo CEO Marc Casper told investors during an earnings call in July the tests are considered the gold standard given their high level of accuracy.