To Interpret the SARS-CoV-2 Test, Consider the Cycle Threshold Value

To prevent the spread of coronavirus disease 2019 (COVID-19), it is important to identify and isolate people who are infectious. It is especially important to ensure that those with a high viral load are isolated and not able to transmit to others. Currently, diagnosis, screening, and surveillance depend on a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcriptasequantitative polymerase chain reaction (RT-qPCR) test, and results are generally reported to the ordering physician as positive or negative. However, the test does provide a measure of the viral load in the sample, in what is called the cycle threshold (Ct) value. We suggest that reporting this Ct value, or a calculated viral load, can aid in interpretation and clinical decisions. We discuss the merits of PCR tests and other approaches, such as time-since-symptomresolution-based approaches for removing individuals from isolation.