Notice of Retraction: Effectiveness of Surgical and Cotton Masks in Blocking SARS-CoV-2

According to recommendations by the editors of Annals of Internal Medicine, we are retracting our article, “Effectiveness of Surgical and Cotton Masks in Blocking SARS-CoV-2. A Controlled Comparison in 4 Patients,” which was published on Annals.org on 6 April 2020 (1).

We had not fully recognized the concept of limit of detection (LOD) of the in-house reverse transcriptase polymerase chain reaction used in the study (2.63 log copies/mL), and we regret our failure to express the values below LOD as “<LOD (value).” The LOD is a statistical measure of the lowest quantity of the analyte that can be distinguished from the absence of that analyte. Therefore, values below the LOD are unreliable and our findings are uninterpretable. Reader comments raised this issue after publication. We proposed correcting the reported data with new experimental data from additional patients, but the editors requested retraction.