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Coronavirus Test Kits Encounter QC Hiccup in Some States, CDC Reports

NEW YORK – Some state laboratories have found that the novel coronavirus 2019-nCoV test kits sent by the US Centers for Disease Control and Prevention have provided inconclusive results during the quality control process, the CDC reported on Wednesday.

As a result, the CDC will likely need to remanufacture one of the kit reagents.

In a call with the media, Nancy Messonnier, the director of the National Center for Immunization and Respiratory Diseases, said that the CDC considers the rapid development and deployment to states of the real-time reverse transcriptase (RT-PCR) diagnostic test kit for 2019-nCoV to be a success. To date, all US states have been shipped 2019-nCoV test kits, as have at least 30 international sites, she said.

Distributing test kits with Emergency Use Authorization to states was "clearly important to try to bring the testing closer to patients, to avoid delays that have been inherent in sending samples to CDC," Messonnier said.

However, the kits, which shipped last week, still had to undergo quality assessment and validation in the state public health labs before they could be used locally.

"When a state gets the test kit, they have to verify that it works the same in their lab as it worked at CDC," Messonnier explained in the press conference. "When some states were doing this, we received feedback that it wasn't working as expected," she said.

Specifically, the QA/QC process in some states yielded inconclusive test results. These were not tests being run on clinical specimens from potential patients, but rather were part of the verification process, Messonnier emphasized.  

Further evaluation has suggested there might be issue with one of the three assays in the test, she said. "We think that it may be that one of the reagents wasn't performing consistently," Messonnier added.

On the agency's website and in the published primers and probes for the test, it describes primer and probe sets including ones for specific detection of 2019-nCoV — so-called N1 and N2 assays — as well as one designed for the universal detection of SARS-like coronaviruses, called the N3 assay. A representative from CDC noted in a follow-up email that the issue is with the third assay.

The CDC will be remanufacturing the particular reagent causing the issue, Messonnier said. "Obviously a state wouldn't want to be doing this test and using it to make clinical decisions if it isn't working as perfectly at state [labs] as it is at CDC," she said.

She emphasized that the QC process is set up specifically to allow for identification of these kinds of problems. "This is part of a normal process and procedure, and redoing the manufacturing is the next step," Messonnier said. "During a response like this, we know things may not always go as smoothly as we like. We have multiple levels of quality control to detect issues just like this one, and we're looking into all of these issues to understand what went wrong and to prevent these same things from happening in the future," she said.

For now, all clinical specimens in the US are still going to the CDC labs for testing and the agency will continue to provide that "backstopping" even after state testing is up and running.

"Of course, we hoped that everything would go smoothly as we rushed through this; we moved quickly, and that is appropriate under these circumstances, but it is equally appropriate to do quality control," Messonnier said.

Not all states have completed the QC process, she also said. Some states may be able to move forward with local testing this week, should it be required, but others may need additional reagents. "I don't have an estimate yet from our laboratory staff as to how long that takes," Messonnier said.