Guidelines for COVID-19 Laboratory Testing for Emergency Departments From the New Diagnostic Technology Team of the Taiwan Society of Emergency Medicine

Abstract

COVID-19 tests have different turnaround times (TATs), accuracy levels, and limitations, which emergency physicians should be aware of. Nucleic acid amplification tests (NAATs) can be divided into standard high throughput tests and rapid molecular diagnostic tests at the point of care (POC). The standard NAAT has the advantages of high throughput and high accuracy with a TAT of 3-4 hours. The POC molecular test has the same advantages of high accuracy as standard high throughput PCR, but can be done in 13-45 minutes. Roche cobas Liat is the most commonly used machine in Taiwan, displaying 99%-100% sensitivity and 100% specificity, respectively. Abbott ID NOW is an isothermal PCR-based POC machine with a sensitivity of 79% and a specificity of 100%. A high rate of false positives and false negatives is associated with rapid antigen testing. Antibody testing is mostly used as part of public health surveys and for testing for immunity.

Keywords: COVID-19; nucleic acid amplification testing; point-of-care testing; rapid point-of-care molecular testing.

Fig. 1. Flowchart for rapid antigen testing in symptomatic and asymptomatic patients

^a Asymptomatic individuals who are fully vaccinated should follow the guidelines regarding testing. Asymptomatic individuals who have had a SARS-CoV-2 infection within the past 3 months should follow the Centers for Disease Control and Prevention (CDC)’s guidance on testing within 90 days of their infection. ^b This antigen negative may need confi rmatory testing if the person has a high likelihood of SARS-CoV-2 infection (e.g., the person has had close contact with or suspected exposure to a person with COVID-19 within the last 14 days, and the person is not fully vaccinated and has not had a SARS-CoV-2 infection in the last 3 months). ^c It may be necessary to confi rm this antigen positive if the person has had a low likelihood of SARS-CoV-2 infection (e.g., the individual has had no exposures to COVID-19 within the past 14 days or has been fully vaccinated). ^d The antigen negative may not need to be confi rmed if the person has a low likelihood of infection with SARS-CoV-2 (see above). ^e An antigen positive result might need confi rmation if the person has a relatively low likelihood of SARS-CoV-2 infection (as described above). ^f For those who are traveling or have recently traveled, refer to the CDC’s guidance for domestic and international travel during the COVID-19 pandemic. ^g Those who are fully vaccinated and those who had a SARS-CoV-2 infection within the last 3 months do not require quarantine. Those who have had contact with a COVID-19-infected person within the past 14 days should consider serial antigen testing. See the CDC’s Options to Reduce Quarantine for guidance on the use of antigen tests in ending quarantine.