Florida Department of Health mandates reporting of cycle threshold values for PCR tests


The Florida Department of Health quietly sent out a memo by email on Friday afternoon, mandating that “Cycle threshold (CT) values and their reference ranges, as applicable, must be reported by laboratories to FDOH via electronic laboratory reporting or by fax immediately.”

The full memo can be read here.

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The most common type of COVID-19 testing uses a technology called polymerase chain reaction (PCR), in which a sample is doubled until the amount of viral material exceeds a threshold. The cycle threshold is the value at which the sample exceeds the threshold, and various scientific papers recommend a maximum of 25-34 cycles to detect viral material that can be grown in culture (thus more likely to indicate that the patient is infectious). It is common for COVID-19 tests to run 38-40 doubling cycles, resulting in some unknown number of positive results for people who are not infectious.

It is unclear whether these results will be publicized or whether this is a first step toward changing the definition of a COVID-19 case in Florida.