Coronavirus Disease 2019 (COVID-19)

Frequently Asked Questions

   
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COVID-19 FAQs

As a trusted healthcare partner, ARUP is committed to not only providing timely, accurate test results that inform optimal patient care, but also to providing accurate, up-to-date information that allows patients and the general public to stay current on the rapidly changing COVID-19 testing environment.

 

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What is COVID-19? What is SARS-CoV-2?

COVID-19 infection is caused by the SARS-CoV-2 virus, which is responsible for the current global pandemic. For U.S. case counts, refer to the CDC.1 SARS-CoV-2 spreads from person to person by respiratory droplets and is mostly easily transmitted when people are in close contact with one another.

What does “herd immunity” mean?

Herd immunity refers to the idea that when a majority of a population is immune to an infectious disease, the rate of spread decreases, and this confers indirect protection to those who are not immune. It is important to note, however, that even if herd immunity is established, nonimmune individuals can still become infected if they are exposed to someone with the disease. Most experts believe that approximately two-thirds of a population would need to have had COVID-19 infection before a community achieves herd immunity.

What are the different categories of COVID-19 testing?

COVID-19 testing falls into two categories: viral detection and antibody testing (also known as serology testing).

Understanding COVID-19 Tests

Test Purpose Benefits of Results

Viral detection testing

Includes nucleic acid amplification (NAA) and antigen tests

Detect current SARS-CoV-2 infection

Inform individuals of their current infection status, which allows them to self-isolate to protect others

Antibody (serology) testing Screen for antibodies to SARS-CoV-2, which indicate possible exposure to the virus

Inform individuals of their possible vulnerability to infection

Identify individuals who have developed antibodies to SARS-CoV-2 and who may qualify to donate convalescent plasma for treatment

Enable estimation of seroprevalence of the virus in the general population

What is COVID-19 molecular viral detection testing?

COVID-19 molecular diagnostic testing is performed to detect SARS-CoV-2, the virus that causes COVID-19 disease. There are two commercially available COVID-19 molecular test types: polymerase chain reaction (PCR) and nucleic acid amplification (NAA) tests. These tests are usually performed on a nasopharyngeal (NP), oropharyngeal (OP), or saliva specimen that is sent to a laboratory for analysis. Some of these tests are performed at the point of care so that results are available within hours, and others are performed by laboratories, a process that can take 1-4 days.

What is COVID-19 antigen testing?

Antigen testing, performed on nasal or throat swabs, can also be used to detect SARS-CoV-2 infection. Antigen testing is often performed at the point of care, allowing for quicker results.2

This testing is useful in the early stage of infection (within the first 5 days symptoms are experienced).2

How does COVID-19 viral detection testing differ from COVID-19 antibody testing?

COVID-19 viral detection testing is used to diagnose active infection, usually requires a respiratory sample or saliva, and may be performed at the point of care or in a laboratory.3

COVID-19 antibody testing is used to detect past exposure to the virus and is performed on a blood sample at the point of care or in a laboratory.4

Who should be tested for a current COVID-19 infection?

The CDC and the Infectious Diseases Society of America (IDSA) recommend that all symptomatic individuals with signs or symptoms consistent with COVID-19 be tested by nucleic acid amplification (NAA) or antigen testing.5,6 NAA testing is the gold standard for detection of SARS-CoV-2 virus.5,6

Diagnostic testing for asymptomatic individuals with known or suspected recent exposure to SARS-CoV-2 may also be advised.5,6

Should asymptomatic individuals be tested for COVID-19 infection?

In some cases, testing may be recommended even if an individual does not have symptoms. For example, testing may be warranted for individuals with a suspected exposure to someone diagnosed with COVID-19.5,6

All individuals, including those who are asymptomatic, who live or work in a long-term care facility or nursing home should undergo testing for SARS-CoV-2.5

How are specimens collected for COVID-19 viral detection testing?

Nasopharyngeal (NP) specimens, the gold standard for viral detection, are collected by inserting a swab through the nose to the back of the throat. Saliva specimens are usually self-collected under healthcare provider supervision. Some laboratories accept other respiratory swabs, including oropharyngeal (OP), midturbinate, or anterior nares swabs.2,6

Are saliva specimens as effective for detecting SARS-CoV-2 as respiratory specimens?

Yes. Recent studies, including one performed by researchers at ARUP and University of Utah Health, found that self-collected saliva and nasopharyngeal (NP) swabs collected by healthcare providers are equally effective for detecting SARS-CoV-2.7 Both saliva and NP swabs are superior to anterior nasal swabs. The study , published in the Journal of Clinical Microbiology, represents one of the largest COVID specimen-type comparisons to date.7

How long does it take to get diagnostic test results?

ARUP currently reports diagnostic test results within 1-4 days. Turnaround times vary by performing laboratory, and increases in testing demand may cause delays in reporting results.

What happens to diagnostic test results?

Diagnostic test results are sent to the ordering clinician and, because COVID-19 is a nationally reportable disease, all COVID-19 test results, regardless of whether they are positive, are reported to state health departments for public health tracking purposes.

Can COVID-19 test results help determine when it is safe to stop isolating?

Specific criteria for returning to work and other settings may vary from place to place. Refer to the CDC’s Interim Guidance for Discontinuation of Isolation for Persons with COVID-19 Not in Healthcare Settings for more information.

What is antibody (serology) testing?

When people are infected with a virus, they begin to develop antibodies, proteins in the blood that attach to the virus and help the body eliminate it. Antibody tests, also commonly referred to as serology tests, are used to investigate whether a person has been exposed to a specific type of virus or bacteria. It takes time for the body to mount an immune response to an infection. Because antibodies do not begin to appear until later in an infection, antibody testing is not recommended for diagnosis during the active, or symptomatic, phase of infection.8

What is the difference between IgM, IgG, and IgA antibodies? Is it necessary to be tested for all of them?

Generally, IgM antibodies are the first antibodies the body produces in response to an infection, usually appear within a week of infection, and disappear within a month or two. IgG antibodies typically develop after IgM and may remain detectable for months or years, although the time period that IgG antibodies persist in those who have had COVID-19 is still being determined. Because IgG antibodies are present for a longer period, they provide the best evidence of past infection. Very little is known about IgA antibody response in SARS-CoV-2 infection.8

Because antibody testing is not recommended to diagnose active COVID-19 infection but instead to detect exposure to the virus, IgG antibodies alone should provide adequate information.

What does the COVID-19 IgG antibody test do?

The COVID-19 IgG antibody test detects IgG antibodies against the SARS-CoV-2 virus. These antibodies provide evidence of exposure to the virus.

How does COVID-19 antibody testing differ from COVID-19 viral detection testing?

COVID-19 antibody testing is performed on a blood sample and is used to detect past exposure to the virus. Antibody testing is appropriate for individuals who may have been infected in the past (at least 2 weeks before testing). This test should NOT be used to diagnose COVID-19.8

COVID-19 viral detection testing is used to diagnose active infection. This testing is usually performed on a respiratory or saliva sample.9

Who is a candidate for COVID-19 antibody testing?

Antibody testing is appropriate for individuals who may have been infected with SARS-CoV-2 in the past (at least 2 weeks before testing).

Antibody testing is not appropriate if an individual has active symptoms (eg, cough, fever) or has had recent possible exposure to SARS-CoV-2.4

If someone received a negative COVID-19 molecular test result, is it appropriate to have antibody testing?

Possibly. COVID-19 molecular testing can sometimes return false-negative results (for example, if an individual is tested late in the course of infection). In this scenario, an antibody test may be helpful to determine if there is evidence of exposure to the virus.

If someone was tested and diagnosed with COVID-19, is there any reason to have antibody testing?

Possibly. If the person was diagnosed with SARS-CoV-2 infection at least 14 days before, an antibody response to the virus likely occurred. An antibody test can provide evidence of this immune response.

What is involved in the COVID-19 antibody testing process?

Antibody testing requires collection of a blood sample that is then chemically analyzed in a laboratory.

How long does it take to get antibody test results?

ARUP currently returns antibody test results within 1-5 days. Turnaround times vary by performing laboratory, and increases in testing demand may cause delays in reporting results.

What happens to antibody test results?

Antibody test results are sent to the ordering clinician and, because COVID-19 is a nationally reportable disease, all COVID-19 antibody test results, regardless of whether they are positive, are reported to state health departments for public health tracking purposes.

Can COVID-19 antibody test results help determine when it is safe to stop isolating?

Specific criteria for returning to work and other settings may vary from place to place. Refer to the CDC’s Interim Guidance for Discontinuation of Isolation for Persons with COVID-19 Not in Healthcare Settings for more information.

What does a negative molecular COVID-19 test result mean? Is retesting ever recommended?

A negative result means that the person tested most likely did not have an active COVID-19 infection at the time the sample was collected.6 Infection may still occur at a later time.

False-negative results are possible, so retesting might be recommended if a clinician still suspects COVID-19.6

What does a positive molecular COVID-19 test result mean?

A positive result means that the patient has an active COVID-19 infection and, in accordance with CDC guidance, should self-isolate and stay away from others.4 The CDC recommends waiting until symptoms completely resolve, fever hasn’t reoccurred for at least 3 days, and 10 days have passed since symptoms first appeared.9

In the event of breathing trouble or other emergency warning signs (eg, persistent pain or pressure in the chest, new confusion, bluish lips or face), emergency medical care should be sought.

Is there a chance that molecular test results could be inaccurate?

No test is perfect. Occasionally, tests can yield a false-positive or false-negative result. Molecular diagnostic testing is highly specific, meaning that the test is designed to detect the unique genetic sequence of SARS-CoV-2. If a test result is positive, you can be confident that the virus was detected.

False-negative results may occur depending on the specimen tested and the timing of the sample collection. Research has shown that nasopharyngeal (NP) swabs and saliva provide the highest concentration of virus; a specimen collected from the oropharynx or nose may not contain enough viral concentration to be detected by the test. Samples should also be collected as near to the time of symptom onset as possible. If testing is performed early in the infectious process, before symptoms occur, test results may be falsely negative. A false-negative result is also possible if a person is tested late in the course of the infection, when symptoms have waned.

What does a positive COVID-19 antigen test result mean?

Positive antigen test results should be interpreted in the context of clinical observations, patient history, and local epidemiologic information.10

In populations experiencing high SARS-CoV-2 positivity rates, positive test results indicate the presence of SARS-CoV-2 antigens.10

False-positive test results are possible and are most likely to occur in populations in which the prevalence of SARS-CoV-2 infection is low. If a false- positive test result is suspected, retesting with a molecular test might be considered.2

What does a negative COVID-19 antigen test result mean?

Negative antigen test results should be considered in the context of clinical observations, patient history, and local epidemiologic information. Antigen testing is less sensitive than nucleic acid amplification (NAA) testing, and there is an increased chance of false-negative results. If a false -negative result is suspected, confirmation testing by NAA may be advised.2,10

However, it is not necessary to perform confirmatory testing in the event of a negative result for an individual who is asymptomatic without known exposure, or when a negative result is obtained during routine screening or surveillance.2

What does a positive COVID-19 antibody test result mean?

A positive test means that antibodies to SARS-CoV-2 were detected and that exposure to the SARS-CoV-2 virus most likely occurred.4 A positive COVID-19 IgG test result usually means that the individual tested has cleared the infection and is no longer contagious, but there is no guarantee of that. Therefore, patients who test positive for antibodies to SARS-CoV-2 should still take precautions to protect themselves and others.4

A positive result does NOT guarantee either current or future immunity to the virus.4 Researchers do not know how long COVID-19 IgG antibodies persist, or the level and duration of protection that they may provide.4

What does a negative COVID-19 antibody test result mean?

A negative COVID-19 IgG test means that antibodies to SARS-CoV-2 were not detected.4 This could suggest that exposure did not occur, that an exposure occurred too recently for an antibody response to develop, or that exposure did not result in the production of enough antibody to be detected by the test.4 Therefore, patients who test negative for SARS-CoV-2 antibodies may still be at risk of SARS-CoV-2 infection and should still take steps to protect themselves and others from infection.4

Negative antibody test results do not rule out SARS-CoV-2 infection.

What does an indeterminate COVID-19 IgG antibody test result mean?

An indeterminate result means that the test was neither clearly positive nor clearly negative. Retesting after a period of time may be appropriate.

Is there a chance that antibody test results could be inaccurate?

No test is perfect. Occasionally, antibody tests can return false-positive or false-negative results. If a specimen is collected too early, antibody tests can yield false-negative results. False-positive results are possible in a small percentage of individuals. These may be due to past or present infection with non-SARS-CoV-2 coronavirus strains, such as coronavirus HKU1, NL63, OC43, or 229E.

 

Do you have additional questions? Visit our COVID-19 Resource Center for further information.

Back to COVID-19 Resource Center

References

  1. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). CDC COVID data tracker. [Updated daily; Accessed: Sep 9, 2020]
  2.  U.S. Department of Health and Human Services, Food and Drug Administration. FAQs on testing for SARS-CoV-2. [Updated: Sep 2, 2020; Accessed: Sep 2, 2020]
  3. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Test for current infection. [Updated: Aug 24, 2020; Accessed: Sep 9, 2020]
  4. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Test for past infection. [Updated: Jun 30, 2020; Accessed: Sep 9, 2020]
  5. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Testing overview. [Updated: Aug 24, 2020; Accessed: Sep 9, 2020]
  6. Hanson KE, Caliendo AM, Arias CA, et al. Infectious Diseases Society of America guidelines on the diagnosis of COVID-19. [Published: May 6, 2020; Accessed: Sep 9, 2020]
  7. Hanson KE, Barker AP, Hillyard DR, et al. Self-collected anterior nasal and saliva specimens versus healthcare worked-collected nasopharyngeal swabs for the molecular detection of SARS-CoV-2. J Clin Microbiol. [Published online ahead of print, Aug 12, 2020]. PubMed
  8. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Interim guidelines for COVID-19 antibody testing. [Updated: Aug 1, 2020; Accessed: Sep 9, 2020]
  9. U.S. Department of Health and Human Services. Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). When you can be around others. [Updated: Sep 10, 2020; Accessed: Sep 11, 2020]
  10. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Interim guidance for rapid antigen testing for SARS-CoV-2. [Updated: Aug 29, 2020; Accessed: Sep 9, 2020]

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