Review of Diagnostic Testing for SARS–CoV-2

Cheng MP, Papenburg J, Desjardins M, et al.
Diagnostic Testing for Severe Acute Respiratory Syndrome–Related Coronavirus-2: A Narrative Review. Ann Intern Med 2020;Apr 13:[Epub ahead of print].

The following are 10 key points to remember from this excellent review on the current state of diagnostic testing for COVID-19 infections:

  1. Given the lack of effective vaccine or treatments, the only currently available strategy to slow the pandemic is through identifying and isolating contagious persons through early and massive deployment of severe acute respiratory syndrome–related coronavirus-2 (SARS–CoV-2) testing.
  2. Diagnostic testing capacity in the United States was limited at the beginning of the outbreak largely due to regulatory hurdles in allowing the use of new tests.
  3. Serum and urine are negative for the presence of viral nuclear acid, regardless of illness severity.
  4. Serologic tests to identify antibodies to SARS–CoV-2 have limited utility given antibody responses to infection take days to weeks to be detectable, and cross-reactivity with other coronavirus proteins can potentially occur. Testing for the purpose of assessing immunity is still being explored.
  5. The diagnostic strategy recommended by the Centers for Disease Control and Prevention (CDC) relies on the collection of respiratory tract samples to assess for the presence of nucleic acid targets specific to SARS–CoV-2. A nasopharyngeal flock swab is preferred. Antigen detection tests have traditionally suffered from suboptimal sensitivity.
  6. The CDC recommends testing in three groups: hospitalized patients suspected of COVID-19, patients at high risk of poor outcomes, and persons who had close contact with someone with suspected or confirmed COVID-19. Testing in asymptomatic persons is NOT recommended.
  7. Concomitant infections with COVID-9 have been reported in up to 60%. Thus, COVID-19 cannot be ruled out by detection of another respiratory pathogen.
  8. At least two negative upper respiratory tract samples collected at 24-hour intervals are required to document SARS–CoV-2 clearance.
  9. Chest imaging, notably computed tomography, is highly sensitive (78-100%) in the diagnosis of COVID-19, but lacks specificity.
  10. Elevations in inflammatory biomarkers such as C-reactive protein, lactate dehydrogenase, and others not specific to COVID-19, have yet to be shown to predict clinical course.

Clinical Topics: Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Heart Failure and Cardiac Biomarkers, Computed Tomography, Nuclear Imaging

Keywords: Antibody Formation, Biomarkers, Pharmacological, Coronavirus, Coronavirus Infections, COVID-19, C-Reactive Protein, Diagnostic Imaging, L-Lactate Dehydrogenase, Pandemics, Respiratory System, SARS Virus, Secondary Prevention, Severe Acute Respiratory Syndrome, severe acute respiratory syndrome coronavirus 2, Tomography, X-Ray Computed

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