The SARS-CoV-2 tests developed by the US Centers for Disease Control and Prevention early in the COVID-19 pandemic suffered from both contamination and a design flaw, the New York Times reports.
In early 2020, the CDC developed a PCR-based test for SARS-CoV-2, but shortly after tests were distributed to state laboratories, some labs received inconclusive results during the quality control process, as GenomeWeb reported at the time. This led the CDC to re-manufacture one of the testing kit reagents, but the delay slowed testing for the virus in the US.
The CDC conducted an internal investigation of what went wrong with their SARS-CoV-2 test, which it now reports in PLOS One. They traced the source of the false positives to cross-reactivity between one of the probes and one of the primers, something the University of Southern California's Susan Butler-Wu tells the Times should have been noticed during the design phase. The CDC team further found that some of the testing material was contaminated with a synthetic template — which was used to gauge if the tests were working properly, according to the Times — during the bulk manufacturing process, as both were made at the same facility.
"In a PhD laboratory, it's an innocent mistake, and you learn and move forward," eMed's Michael Mina, who developed PCR tests for the virus, tells the Wall Street Journal. "When it's the CDC in the midst of a global crisis and there are working assays around the world already, we have to be really darn sure that we have done all of our due diligence."
Still, Stanford Health Care's Benjamin Pinsky tells the Times that "it's important that they got to the bottom of what went wrong."