COVID-19 - Laboratory Testing in the United States

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Viral (nucleic acid or antigen) tests are used to diagnosed COVID-19 by testing respiratory samples for SARS-CoV-2.  Available tests range from point-of-care tests (taking less than 1-hour) to taking 1-2 days to result. Antibody testing is also available, but this is not used to diagnose acute COVID-19 infection. Only viral tests are used to diagnose acute infection.  The role of serologic testing is currently under exploration.  It is not clear, at this time, if a positive serologic test confers immunity, so this should not be assumed.  

Guidelines for collection and handling of laboratory specimens can be found here.

The following information outlining testing guidelines was pulled obtained from the CDC's website for accuracy and can be found here.

The CDC describes five categories of people for SARS-CoV-2 testing with viral tests (i.e., nucleic acid or antigen tests):

Generally, viral testing for SARS-CoV-2 is considered to be diagnostic when conducted among individuals with symptoms consistent with COVID-19 or among asymptomatic individuals with known or suspected recent exposure to SARS-CoV-2 to control transmission, or to determine resolution of infection. Testing is considered to be surveillance when conducted among asymptomatic individuals without known or suspected exposure to SARS-CoV-2 for early identification, or to detect transmission hot spots or characterize disease trends.

Recommended testing for individuals with signs or symptoms consistent with COVID-19

CDC recommends using authorized nucleic acid or antigen detection assays that have received an FDA EUA to test persons with symptoms when there is a concern of potential COVID-19. Tests should be used in accordance with the authorized labeling; providers should be familiar with the tests’ performance characteristics and limitations.

Clinicians should use their judgment to determine if a patient has signs or symptoms compatible with COVID-19 and whether the patient should be tested. Most patients with confirmed COVID-19 have developed fever and/or symptoms of acute respiratory illness (e.g., cough) but some infected patients may present with other symptoms as well. Clinicians are encouraged to consider testing for other causes of respiratory illness, for example influenza, in addition to testing for SARS-CoV-2 depending on patient age, season, or clinical setting; detection of one respiratory pathogen (e.g., influenza) does not exclude the potential for co-infection with SARS-CoV-2. Because symptoms and presentations may be different in children, consider referencing the CDC guidelines for COVID in neonates and for multisystem inflammatory syndrome in children (MIS-C).

The severity of symptomatic illness due to infection with SARS-CoV-2 may vary. Among persons with extensive and close contact to vulnerable populations (e.g., healthcare personnel [HCP]), even mild signs and symptoms (e.g., sore throat) of possible COVID-19 should prompt consideration for testing. Additional information is available in CDC’s Interim U.S. Guidance for Risk Assessment and Public Health Management of Healthcare Personnel with Potential Exposure in a Healthcare Setting to Patients with Coronavirus Disease 2019 (COVID-19).

Recommended testing for asymptomatic individuals with known or suspected exposure to SARS-CoV-2 to control transmission

Testing is recommended for all close contacts of persons with SARS-CoV-2 infection, especially initial testing during an outbreak or pandemic due to the high likelihood of exposure. Because of the potential for asymptomatic and pre-symptomatic transmission, it is important that contacts of individuals with SARS-CoV-2 infection be quickly identified and tested.

In some settings, broader testing, beyond close contacts, is recommended as a part of a strategy to control transmission of SARS-CoV-2.  This includes high-risk settings that have potential for rapid and widespread dissemination of SARS-CoV-2 (e.g., meat processing plant) or in which populations at risk for severe disease (e.g., long-term care facilities, including nursing homes, intermediate care facilities for individuals with intellectual disabilities, and psychiatric residential treatment facilities) could become exposed.  Expanded testing might include testing of all contacts in proximity to someone with SARS-CoV-2 infection, or even testing all individuals within a shared setting (e.g., facility-wide testing). Currently CDC recommends expanded contact testing in the following guidance documents:

Recommended testing for asymptomatic individuals without known or suspected SARS-CoV-2 exposure for early identification in special settings

Certain settings can experience rapid spread of SARS-CoV-2, resulting in substantial adverse effects. This is particularly true for settings that house vulnerable populations in close quarters for extended periods of time (e.g., long-term care facilities, correctional and detention facilities) and/or settings where critical infrastructure workers (e.g., healthcare personnel, first responders) may be disproportionately affected.

A strategy aimed at reducing introduction of SARS-CoV-2 into the setting through early identification could reduce the risk of widespread transmission in these situations.

Facilities are encouraged to work with local, territorial, and state health departments to help inform decision-making about broad-based testing. Before testing large numbers of asymptomatic individuals without known or suspected exposure, the facility should have a plan in place for how it will modify operations based on test results.

Approaches for early identification of asymptomatic individuals include:

  • Initial testing of everyone residing and/or working in the setting,
  • Regular (e.g., weekly) testing of everyone residing and/or working in the setting, and
  • Testing of new entrants into the setting and/or those re-entering after a prolonged absence (e.g., one or more days)

Settings for which these approaches could be considered include:

  • Long-term care facilities
  • Correctional and detention facilities
  • Homeless shelters
  • Other congregate work or living settings including mass care, temporary shelters, assisted living facilities, and group homes for individuals with intellectual disabilities and developmental disabilities
  • High-density critical infrastructure workplaces where continuity of operations is a high priority

CDC guidance currently addressing such testing includes:

Julie Grishaw, ACNP

Senior Editor, McGraw-Hill Education

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