aIdeal use only in high-prevalence (>5–10%) scenarios with symptomatic patients or selected settings (e.g. emergency rooms, elderly residences, healthcare personnel, and surgical urgencies). The best timeframe for collection in asymptomatic individuals is 5–7 days after the close contact. Providers conducting testing on asymptomatic populations must be aware of the potential for a presumed false-positive result with an antigen test that will necessitate confirmation with a subsequent RT-PCR test (Virginia Department of Health, 2020).
bConsider the interpretation of the result as ”Confirmed exposure to SARS-CoV-2”. In the case of IgM positivity only, consider as a probable false positive (Kubina and Dziedzic, 2020) and repeat determination with other methods, such as high-affinity antibody assays (total immunoglobulins or IgG).
cConsider PCR pooling for population screening with low pre-test probability (<10%) to ensure assay cost-effectiveness or in negative antigen patients. If the pooling result is positive, individual RT-PCR must be performed for each pooled sample, so the maximum recommended pool size is 10 (CDC, 2020a).
dConsider multiplex RT-PCR, including influenza A/B or respiratory panel with influenza, RSV, and other viral/bacterial/fungal pathogens (Kim et al., 2020) (Zhu et al., 2020). The presence of other respiratory viruses does not rule out co-infection by SARS-CoV-2, therefore this possibility should not be neglected (and should be thoroughly investigated if the clinical-epidemiological context is suggestive of such).
eConsider antibody tests if other results are negative.
fConsider Day 14 of symptoms or Day 21 of close contact.
Ig, immunoglobulin; PCR, polymerase chain reaction; rRT-PCR, real-time reverse transcription PCR; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; RSV, Respiratory Syncytial Virus