1/21/2021: [The role of cycle threshold values in infectious disease diagnostics](https://www.mlo-online.com/continuing-education/article/21206319/the-role-of-cycle-threshold-values-in-infectious-disease-diagnostics) > Ct values in COVID-19 >> Without a standard curve, Ct values can still provide an indirect, relative quantification of pathogen load; however, it is important to keep in mind that Ct values can only be compared if the reaction efficiency is similar and the target genes have the same number of copies.4 This additional layer of complexity in understanding Ct values may limit a broader use of this data, narrowing use to only those personnel who have been trained to understand and appropriately interpret data from RT-PCR tests. >> While the results of SARS-CoV-2 PCR diagnostic assays remain – in the majority of cases – reported as positive or negative results in the clinical setting, a discussion has emerged about the possibility of reporting and interpreting Ct values to aid clinicians in patient management. The increasing evidence supporting the utility of Ct values has led public health authorities, such as Public Health England and the Centers for Disease Control and Prevention (CDC), to develop guidance and recommendations regarding their use. **Experts agree that if Ct values are to be reported, linearity, limits of detection and reference quantification curves must be standardized and validated. Interpretations of a single positive Ct value may be of limited use in the clinic.**13, 14 However, indications are emerging that serial Ct values may offer greater utility for the purpose of clinical management.13 1/19/2021: [Your Coronavirus Test Is Positive. Maybe It Shouldn’t Be.](https://www.nytimes.com/2020/08/29/health/coronavirus-testing.html) Standard curve needs to be surpassed for someone to be labelled covid positive now by the WHO. 1/20/2021: [Nucleic acid testing (NAT) technologies that use polymerase chain reaction (PCR) for detection of SARS-CoV-2](https://www.who.int/news/item/20-01-2021-who-information-notice-for-ivd-users-2020-05) > WHO reminds IVD users that disease prevalence alters the predictive value of test results; as disease prevalence decreases, the risk of false positive increases (2). This means that the probability that a person who has a positive result (SARS-CoV-2 detected) is truly infected with SARS-CoV-2 decreases as prevalence decreases, irrespective of the claimed specificity.