“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.“ https://www.who.int/news/item/20-01-2021-who-information-notice-for-ivd-users-2020-05 … Continue reading PCR and the Prevalence Problem