The original CDC test relied on three “primer” sets, small snippets of DNA that match the unique sequences of the coronavirus, to check for its presence in a patient swab sample. Labs widely found the third primer in the test kit did not give accurate readings. On Wednesday, the CDC gave permission for labs finding the other two primers reliable to proceed by throwing out the third one. But the New York labs and a few others have claimed that the first primer was also unreliable.

New York City Department of Health and Mental Hygiene Deputy Commissioner Demetre Daskalakis confirmed that New York City and New York State public health labs found problems in their use of the original CDC test kit. The FDA gave the labs permission to work on their own genetic test for the virus, an unprecedented move for state labs, and they are first in line for a brand-new CDC test still under development.

“The only question is which will come on line first,” Daskalakis said.