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A Number on It

Public health officials and others are debating whether patients' cycle threshold (CT) values should be included on their SARS-CoV-2 testing results, according to Science magazine.

Proponents of adding CT values to test results note there is increasing evidence that having a low CT value — meaning that fewer PCR cycles were needed to pick up evidence of infection — is linked to a higher risk of serious disease and of being infectious, it adds. They further argue that CT values could be used to prioritize individuals for contact tracing and give a glimpse into whether an outbreak is on the rise or decline.

However, others point out that CT values can vary from machine to machine and between swabs from the same person, Science notes.

Chanu Rhee, a hospital epidemiologist at Brigham and Women's Hospital, tells it that a CT value isn't all she would use to evaluate patients. "But I do still find it helpful," she adds.