Coronavirus Disease 2019 (COVID-19)

Frequently Asked Questions

   
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COVID-19 FAQs

As a trusted healthcare partner, ARUP is committed not only to 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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Does molecular viral detection testing detect the novel United Kingdom, Brazilian, and South African variants or other variants of SARS-CoV-2 with mutations in the spike protein (S gene)?

ARUP is currently using three molecular platforms to test for SARS-CoV-2 (Thermo Fisher, Roche, and Hologic). Of these, only the Thermo Fisher assay uses the spike protein (S gene) as a target for SARS-CoV-2 identification. Because of this, only the Thermo Fisher assay is at risk of failing to detect the virus in samples with variants containing S gene mutations, such as the United Kingdom (UK), Brazilian, or South African (SA) variants. However, the Thermo Fisher assay utilizes multiple targets, so it still detects variants with S gene mutations. The Roche and Hologic assays do not use the S gene as an amplification target and their performance is unaffected by S gene mutations. The table below details the gene targets of ARUP’s SARS-CoV-2 assays. All of the assays in the table below can detect the UK, Brazilian, and SA variants of SARS-CoV-2.

ARUP SARS-CoV-2 Assay Gene Targets

Assay Gene Targets

Thermo Fisher RT-PCR

Orf1ab/O-methyltransferase gene
N gene
S gene

Roche RT-PCR

Orf1ab/O-methyltransferase (2 different sites)
Env E-gene/pan-sarbecovirus

Hologic RT-PCR

Orf1ab/O-methyltransferase (2 different sites)

Hologic TMA

Orf1ab/O-methyltransferase (2 different sites)

RT-PCR, reverse transcription polymerase chain reaction; TMA, transcription-mediated amplification

The Thermo Fisher assay utilizes three gene targets for the detection of SARS-CoV-2 (Orf1ab/O-methyltransferase, N gene, and S gene). For this assay to return a positive result, two of the three targets must be amplified. ARUP has observed lack of amplification of the S gene in some variants, including the UK variant, but because of amplification in the other two targets, the assay still yielded a positive result. It is important to note that lack of amplification of the S gene does not necessarily indicate the presence of the UK or SA variant. Likewise, S gene mutations do not necessarily cause S gene dropout. Genetic sequencing is required to fully characterize and identify a particular SARS-CoV-2 strain.

There is a possibility that these variants may result in low-positive samples that are positive for only Orf1ab/O-methyltransferase and N gene targets and yield an “inconclusive” result. It is also possible that different variants may result in amplification of the S gene but would be Orf1ab/O-methyltransferase and N gene negative, but these different variants are likely rare at this time.

More information about COVID-19 variants can be found on the CDC’s website.1 Additionally, you can refer to this FDA Letter to Healthcare Providers2 for more information about SARS-CoV-2 variants and their possible impact on laboratory testing.

What steps is ARUP taking to identify major variants, such as those found in the United Kingdom and South Africa, and determine how they impact laboratory testing?

To characterize potential mutations, ARUP is currently sequencing variants that exhibit S gene dropout in the Thermo Fisher standalone COVID-19 assay. S gene dropout does not necessarily indicate the presence of a United Kingdom (UK) or South African (SA) variant because there are several circulating strains with mutations in this region. ARUP does not release sequencing variant information for individual patients; sequencing is performed by ARUP for epidemiologic purposes and to monitor and improve assay performance.

The dropout of the S gene target, with continued positivity for the Orf1ab/O-methyltransferase and N gene targets in Thermo Fisher’s standalone COVID-19 assay, has enabled the identification of UK strains in the United States. ARUP is currently sequencing a subset of samples with anomalous S gene amplification and is also involved in ongoing sequencing projects to characterize other circulating strains, not just the UK and SA variants.

When using the Thermo Fisher assay, there may be some very low-positive samples that are positive for only Orf1 or N and are called inconclusive, or some samples that would have been positive based on amplification of the S gene but are Orf1 and N negative (and thus yield negative results because this assay depends on amplification of two of the three targets). However, these instances are likely rare at this time.

We are constantly investigating and adapting our new technologies to the unpredictable dynamics of this pandemic, and our current methodologies may change in accordance with pertinent and persuasive data.

Does ARUP have a SARS-CoV-2 sequencing test available to order?

ARUP does not offer a SARS-CoV-2 sequencing test and does not release sequencing variant information for individual patients. However, ARUP has the ability to perform SARS-CoV-2 sequencing and has begun sequencing samples that exhibit S gene dropout on the Thermo Fisher testing platform. This sequencing is performed for epidemiologic purposes, to monitor test performance, and, if necessary, to improve the performance of tests used to diagnose COVID-19.

Are cycle threshold values from RT-PCR testing useful to determine infectivity?

New April 16, 2021

The CDC does not recommend the use of cycle threshold (Ct) values to determine viral load, infectivity, or proper isolation or quarantine times.3 Although there is a correlation between viral load and Ct, it is imperfect and impacted by outside factors such as specimen collection and storage. Additionally, Ct values are not standardized across assays or laboratories. At this time, ARUP does not provide Ct values for individual specimens.

What is multipathogen testing (also called respiratory virus panel testing or cotesting) for SARS-CoV-2?

Multipathogen testing for SARS-CoV-2, also referred to as respiratory virus panel testing or cotesting, refers to tests that are designed to detect and differentiate between multiple viruses, including SARS-CoV-2. This type of testing is useful when multiple viruses with similar symptoms (eg, influenza, respiratory syncytial virus [RSV], and SARS-CoV-2) are circulating at the same time, such as during flu season. These tests may be also be useful to determine if a patient has a simultaneous infection with multiple viruses.4

What is COVID-19 antigen testing?

Updated April 16, 2021

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 because results are available faster than nucleic acid-based assay results.4 A recent ARUP study found that one point-of-care antigen testing assay is less sensitive than standard nucleic acid amplification (NAA) tests for the detection of SARS-CoV-2.5 This testing is useful in the early stage of infection (within the first 5 days symptoms are experienced).6

What is the role of viral culture in the diagnosis and management of COVID-19?

New April 16, 2021

Viral culture is not useful for routine diagnosis and management of COVID-19. More information about the use of viral culture to study SARS-CoV-2 can be found on the CDC’s website.4

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

Updated April 16, 2021

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.7,8 NAA testing is the gold standard for detection of SARS-CoV-2 virus.7,8

Diagnostic testing for asymptomatic individuals with known or suspected recent exposure to SARS-CoV-2 may also be advised.7,8

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-19.7,9 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-2.9

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.6,8

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-2.10 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.10 Saliva specimens are not suitable all types of COVID-19 testing. For example, saliva specimens cannot be accepted for ARUP’s combined influenza/SARS-CoV-2/respiratory syncytial virus (RSV) test.

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 Settings11 for more information.

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 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.11

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.12

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.

Who is a candidate for COVID-19 antibody testing?

Updated April 16, 2021

Antibody testing is appropriate for individuals who may have been infected with SARS-CoV-2 in the past (at least 2 weeks before testing). It may also be appropriate if a false-negative diagnostic testing result is suspected (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. Antibody testing is not appropriate if an individual has active symptoms (eg, cough, fever) or has had recent possible exposure to SARS-CoV-2.9

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 Settings11 for more information.

Can serology be used to determine vaccine response?

New April 16, 2021

COVID-19 vaccination produces antibodies against the SARS-CoV-2 spike protein. These antibodies can be detected by several serology tests. However, it has not yet been established that the presence of SARS-CoV-2 IgG antibodies implies protective immunity. There is insufficient data to define a threshold for protective immunity, so we cannot properly interpret whether or not a patient is protected from symptomatic disease or reinfection. The American Association for Clinical Chemistry (AACC) does not currently recommend the use of serology to assess vaccination response.12 More information on the utility of serology in vaccinated individuals can be found in this article.

What do the results of my molecular diagnostic and/or serology test mean?

New April 16, 2021

The table below details the potential results of molecular diagnostic or serology assays and their interpretations.

Test Result Interpretation

COVID-19 molecular diagnostic assays

Positive

The patient has an active COVID-19 infection and should follow the CDC’s guidelines for self-isolation.

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

Negative

The person tested most likely did not have an active COVID-19 infection at the time the specimen was collected. 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.

Indeterminate

The test was neither clearly positive nor clearly negative. Retesting after a period of time may be appropriate.

Invalid

Test results could not be determined. This result could be due to the presence of interfering or inhibiting substances in the specimen. Retesting after a period of time may be appropriate.

COVID-19 serology assays

Positive

Antibodies to SARS-CoV-2 were detected. It is likely that the patient has been exposed to SARS-CoV-2. Serology assays that detect antibodies to the spike protein may also detect antibodies generated in response to COVID-19 vaccination.

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

Negative

Antibodies to SARS-CoV-2 were not detected. 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 antibodies to be detected by the test.

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

Indeterminate

The test was neither clearly positive nor clearly negative. Retesting after a period of time may be appropriate.

Source: CDC, 20217,11

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.

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). New COVID-19 variants. [Updated: Apr 13, 2021; Accessed: Apr 13, 2021]
  2. U.S. Food and Drug Administration. Genetic variants of SARS-CoV-2 may lead to false negative results with molecular tests for detection of SARS-CoV-2: letter to clinical laboratory staff and health care providers. [Published: Jan 8, 2021; Accessed: Apr 13, 2021]
  3. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19).  Clinical questions about COVID-19: questions and answers. [Updated Mar 4, 2021; Accessed: Apr 13, 2021]
  4. National Institutes of Health. Influenza and COVID-19. [Updated: Oct 22, 2020; Accessed: Apr 13, 2021]
  5. Okoye NC, Barker AP, Curtis K, et al. Performance characteristics of BinaxNOW COVID-19 antigen card for screening asymptomatic individuals in a university setting. J Clin Microbiol. 2021;59(4):e03282-20.
  6. U.S. Department of Health and Human Services, Food and Drug Administration. FAQs on testing for SARS-CoV-2. [Reviewed: Mar 25, 2021; Accessed: Apr 13, 2021]
  7. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Testing overview. [Updated: Mar 17, 2021; Accessed: Apr 13, 2021]
  8. 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: Apr 13, 2021]
  9. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). Test for past infection. [Updated: Feb 2, 2021; Accessed: Apr 13, 2021]
  10. 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. 2020;58(11):e01824-20. PubMed
  11. 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: Mar 17, 2021; Accessed: Aprm 13, 2021]
  12. Zhang YV, Wiencek J, Meng QH, et al. AACC practical recommendations for implementing and interpreting SARS-CoV-2 EUA and LDT serologic testing in clinical laboratories. Clin Chem. 2021 [Published online ahead of print Mar 2021].

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