25 Aug Use of SARS CoV-2 Antibody Tests
The diagnosis of acute COVID-19 relies on detection of SARS-CoV-2 RNA by real-time reverse transcription-polymerase chain reaction (PCR) from respiratory samples. Viral shedding from the upper respiratory tract is greatest between the presymptomatic period and within the first week of symptoms but drops off rapidly over time. Despite high specificity, the sensitivity of the SARS-CoV-2 RT-PCR from nasopharyngeal or midturbinate swabs is sub-optimal and may be influenced by timing of the swab, technique and limitations of the assay. Some patients present for testing late in their illness when viral titres in the upper airways are waning, and despite a clinical diagnosis of COVID-19 being made, may test negative by PCR, sometimes repeatedly.