DIAGNOSTIC APPROACH TO COVID-19 Mohammed Ziada MD, Infectious Diseases Fellow
Victoria Burke MD, Assistant Professor of Clinical Medicine Department of Medicine — Section of Infectious Diseases LSU Health Sciences Center, New Orleans, LA
ABSTRACT INTRODUCTION
Accurate and timely diagnosis of SARS-CoV-2 infection is essential to control viral spread.
METHODS
In this article, we review the indications for SARS-CoV-2 testing among both symptomatic and asymptomatic individuals, as well as the general characteristics, indications, and interpretation of the three major classes of COVID-19 diagnostics: nucleic acid amplification testing (NAAT), antigen testing, and antibody testing. In general, NAAT and antigen tests are utilized to make a diagnosis of acute infection. Antibody tests are serologic assays that measure the immune response to SARS-CoV-2 infection and can confirm prior recent infection. They have limited utility in confirming active infection and commercially available assays cannot confirm immunity to SARS-CoV-2.
CONCLUSION
NAAT assays and antigen testing are the major diagnostics utilized to confirm active infection with SARS-CoV-2, whereas, antibody testing is used to confirm prior recent infection.
INTRODUCTION The COVID-19 global pandemic has impacted the entire world over the past year, accounting for over 100 million cases and greater than 2 million deaths worldwide. Accurate and timely diagnosis of SARS-CoV-2 infection is essential to control viral spread to limit further morbidity and mortality from this illness. In this article, we review the indications for SARS-CoV-2 testing among both symptomatic and asymptomatic individuals, as well as the general characteristics, indications, and interpretation of the three major classes of COVID-19 diagnostics: nucleic acid amplification testing (NAAT), antigen testing, and antibody testing. INDICATIONS FOR SARS-COV-2 TESTING There are no specific clinical features that can reliably distinguish COVID-19 fromother respiratory viral infections 1 . Providers should, therefore, have a low threshold for suspicion of COVID-19 in patients with any concerning symptoms, particularly if they have spent time in an area with community transmission or have a close contact with confirmed or suspected COVID-19 in the preceding 14 days. If possible, it is recommended that all symptomatic patients with suspected infection undergo testing for
acute infection.
The Infectious Diseases Society of America (IDSA) has suggested priorities for testing when diagnostic capacity is limited. High-priority individuals include hospitalized patients (especially critically ill patients with unexplained respiratory illness) and symptomatic individuals who are health care workers or first responders, work or reside in congregate living settings, or have risk factors for severe disease 2 . Testing certain asymptomatic individuals may also be important for public health or infection control purposes. Situations where testing of asymptomatic individuals is recommended include the following instances: 2,3
• Following close contact with an individual with COVID-19 without full PPE (this includes neonates born to mothers with active or recent COVID-19). The optimal time to test for COVID-19 following exposure remains uncertain but five to seven days post exposure is largely recommended based on the average incubation period. • Screening residents of congregate living facilities that house individuals at risk for severe disease (e.g., long- 12
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