The New York Times reported in August that some of the nation’s leading public health officials say the standard COVID tests with cycle thresholds at 40 or higher are “diagnosing huge numbers of people who may be carrying relatively insignificant amounts of the virus.” Virologists and most researchers, including the Centers for Disease Control, agree that it is difficult to find live virus capable of transmission beyond 34 cycles. But the Kansas state lab, which conducts about 24% of all tests in the state, is using a cycle threshold of 42 cycles and likely finding dead virus particles that can’t be transmitted to others.
The Sentinel found private labs are also using cycle thresholds above virus viability. Quest Diagnostics, in Lenexa and Salina, sets their cycle threshold at 40. LabCorp, in Kansas City, KS, Kansas City, MO, Lawrence, Overland Park, Salina, and Wichita, sets their PCR test to a cycle threshold of 38.
Michael Mina, an assistant professor of epidemiology at both Harvard Medical School and the Harvard T.H. Chan School of Public Health told Harvard Magazine that reporting someone positive on a test with a high cycle threshold is like finding a hair in a room, testing it for DNA, and then saying the person who shed that hair is currently in the room.
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