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The ability of the cycle threshold to inform the infectivity of SARS-CoV-2 polymerase chain reaction (PCR)-positive individuals remains controversial. Berengua et al. have recently reported that in immunocompetent individuals SARS-CoV-2 infectivity lasts < 15 days and that Ct value > 27 indicates low probability for infectivity. This important study, however, comes with several caveats. The authors performed a single cell culture for each sample. Additionally, cycle threshold values and corresponding viral loads differ between variants. During the study period at least four strains were prevalent in Europe, yet the authors do not provide information regarding the isolated strains. Lastly, this hospital-based study seems to involve sampling bias. The findings of Berengua et al. may be leveraged to guide clinical decision in SARS-CoV-2 PCR-positive convalescing candidates for organ donation or transplantation.
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