Survey on Reporting of Cycle Threshold (Ct) Values in Severe Acute Respiratory Syndrome Coronavirus 2 PCR Testing

Background:The clinical application of cycle threshold (Ct) values for qualitative PCR tests is not recommended.However, if reporting Ct values is unavoidable, comments including warnings regarding their clinical use, the lack of an established correlation with viral load and infectivity, and factors influencing Ct values are recommended.Methods: A survey was conducted among institutions participating in severe acute respiratory syndrome coronavirus 2 PCR proficiency testing in early 2024.The survey examined the reasons for reporting Ct values and whether comments on the clinical implications of Ct values were provided to clinicians.Two laboratory medicine experts designed the survey questions, which were reviewed and then revised based on feedback from five other experts.Results: The survey was distributed to 255 institutions with 160 respondents (71.1%).Among the 160 respondents, 19 (11.8%) did not report the Ct values.Of the 141 institutions reporting Ct values, 98 (69.5%) cited the judgment of laboratory medicine specialists as an associated factor, followed by 88 institutions (62.4%) reporting it at clinician request.Among these 141 institutions, 71 (50.4%) provided comments related to retesting, 32 (22.7%) reported factors influencing Ct values, 20 (14.2%) commented on the early or recovery stages of infection, and only 10 (7.1%) explicitly stated that Ct values were not directly correlated with infectivity or viral load.Conclusions: A vast number of the institutions reported Ct values, but many did not provide comments about the lack of a direct correlation with infectivity or viral load, which requires education on diagnostic stewardship.