Antibody Testing Frequently Asked Questions
Sonora Quest is performing a test kit manufactured by EUROIMMUN, a PerkinElmer company. The assay kit package insert6 states that in the validation of the ELISAs, no cross-reactions to antibodies against worldwide-distributed coronaviruses were detected. Cross-reactions with antibodies against the closely related SARS-CoV(-1) and other known human coronaviruses (HKU1, NL63, OC43, or 229E) cannot be completely excluded. However, the specificity of the SARS-CoV-2 IgG immunoassays (ELISA and CMIA) is approximately 99%. Manufacturers6 tested panels of samples from pre-COVID times (2010, 2017, and 2019), with less than 1% samples showing positive results. These findings suggest that antibodies against SARS-CoV and other coronaviruses are not commonly found in the general public.
As stated in literature provided by EUROIMMUN, analytical specificity of the EUROIMMUN Anti-SARS-CoV-2 ELISA IgG antibody test is 98.5-99%. Due to the low homology of the SARS-CoV-2 S1 protein to the human coronavirus family (HCoV-229E, HCoV-NL63, HCoV-HKU1 or HCoV-OC43), cross-reactions to most of the human pathogenic representatives of this virus family are virtually excluded.
Sensitivity is normally used in the context of measuring sensitivity to detect the disease, however, in the context of serology, you are only measuring sensitivity to antibodies, not SARS-CoV-2. Because antibody testing is not used for diagnosis, sensitivity is less important than specificity. The focus is on maximizing specificity for IgG so that we have no false positives. Sonora Quest ensures that test offered for SARS-CoV-2 IgG is extensively validated by the manufacturer to be highly specific. Sonora Quest is also performing our own validation using stringent acceptability criteria for precision, reproducibility, accuracy, method comparison, cross-reactivity, and clinical performance before starting patient testing.
In medical diagnosis, test sensitivity is the ability of a test to correctly identify those with the disease (true positive rate), whereas test specificity is the ability of the test to correctly identify those without the disease (true negative rate).
Will the antibody testing need to be on its own requisition, or can it be combined with other tests?
The antibody testing does not need to be on its own requisition. However, if you’re submitting both a molecular test and an antibody test, the molecular test must be submitted on its own requisition in its own specimen bag.
To apply for AHCCCS or to obtain additional information, patients can visit https://azahcccs.gov/Members/GetCovered/apply.html or call the Applicant & Member Services 1(855)HEA-PLUS (1-855-432-7587). Calls are answered Monday through Friday 8 a.m. – 5 p.m.
Based on the regulations and expected coverage for testing, for our insured patients, Sonora Quest will bill the patient’s insurance directly. For uninsured patients, Sonora Quest will pursue reimbursement from the Arizona Health Care Cost Containment System (AHCCCS) or the Department of Health and Human Services (HHS). Sonora Quest is not billing patients for this testing when ordered by a physician.
Note that if you would like to order the COVID-19 antibody test without a doctor’s order or insurance, it is available for $99 through our My Lab ReQuestTM solution.
Based on the regulations and expected coverage for testing, Sonora Quest is not billing patients for this testing when ordered by a physician. It is recommended that patients consult with a physician to determine the medical necessity of obtaining COVID-19 testing. A physician ordered test would likely be covered if the order meets coverage guidelines, resulting in zero out-of-pocket expense.
Note that if you would like to order the COVID-19 antibody test without a doctor’s order or insurance, it is available for $99 through our My Lab ReQuestTM solution.
Orders should be submitted to Sonora Quest with all patient demographics and “Uninsured” noted in the payor portion of the order. Sonora Quest will pursue payment through AHCCCS or Department of Health & Human Services and will not be charging the patient.
The price of the test is $65 if billed directly to a healthcare provider’s office, and $99 if billed to insurance or if a patient decides to purchase the test themselves without a doctor’s order or insurance through our My Lab ReQuest™ solution.
Based on the regulations and expected coverage for testing, for our insured patients, Sonora Quest will bill the patient’s insurance directly. For uninsured patients, Sonora Quest will pursue reimbursement from the Arizona Health Care Cost Containment System (AHCCCS) or the Department of Health and Human Services (HHS). Sonora Quest is not billing patients for this testing when ordered by a physician.
There are many point of care (POC) tests out in the market that have not been validated and/or have no EUA from the FDA. Many of these fingerstick tests show false positives or false negatives. This has resulted in the FDA being more restrictive with those testing options. Any test that Sonora Quest offers will be analytically validated to ensure its quality.
IgA and IgM are early indicators of viral exposure and can aid in the diagnosis of COVID-19. They can take 3-7 days to form after initial exposure. IgG, by contrast, typically takes 10-14 days to form after initial exposure and may indicate a prior infection which may be resolved or is still resolving, and/or protection against reinfection (“protective immunity”). At this time, Sonora Quest is focusing its efforts on IgG antibody testing only. Our focus on IgG will enable Sonora Quest to provide antibody testing that provides insights into an individual’s prior exposure to COVID-19 and the potential for protective immunity, which ultimately may help identify people who may be able to resume work and other daily activities in society.
Blood specimens for SARS-CoV-2 antibody testing can be collected by a hospital or health system or in any healthcare setting where a licensed phlebotomist can draw blood. Sonora Quest will be collecting serology specimens at select Patient Service Centers (PSCs) across Arizona. These locations are posted on SonoraQuest.com/coronavirus and are updated on SonoraQuest.com for appointment scheduling. See the list of Patient Service Centers available for scheduling.
No. Only the molecular test (test code 907080 for swab samples and 907078 for lower respiratory samples) should be used to test a symptomatic patient for COVID-19. The IgG antibody test will help to identify people who have been exposed to the SARS-CoV-2 virus and may indicate a prior infection which may be resolved or is still resolving, and/or protection against re-infection (“protective immunity”).
The CPT code for the testing is 86769. CPT codes are based on the American Medical Association (AMA) guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.
IgG antibody testing (test code 907097) should be performed to assess whether someone has been exposed to the SARS-CoV-2 virus in the past. IgG antibody testing should not be used to diagnose active infection, and symptomatic patients should always be diagnosed using a molecular COVID-19 test
(test code 907080 for swab samples and 907078 for lower respiratory samples).
Sonora Quest initially expects to be able to run 1,000 – 3,000 tests per day and is continuing to scale up testing capacity on the antibody platform.
Turnaround time for the antibody test is typically 1-4 days from the time of collection but can vary due to high demand.
Specimen stability for the antibody test is as follows:
- Room temperature: 5 days
- Refrigerated (2 °C–8 °C): 7 days
- Frozen (-20 °C): 7 days
Specimens should be transported refrigerated to Sonora Quest according to standard operating procedures. Cold packs/pouches must be used if placing specimens in a lockbox for courier pick-up. STAT pick-up cannot be ordered for this test. The COVID-19 antibody test does not need to be ordered on its own separate requisition.
The supplies needed are serum separator vacutainer tubes (SSTs).
The required volume is 1.0 mL (0.5 mL minimum) of serum.
A serum sample obtained by taking a blood sample.
It usually takes at least 10 days after symptom onset for IgG to reach detectable levels. Based on a recent study of 173 hospitalized patients in China,1 all patients (100%) developed antibodies against SARS-CoV-2. The median time to have detectable (IgG) antibodies (called seroconversion) was 11 to 14 days.
SARS-CoV-2 antibody tests are designed to detect specific antibodies against this virus. A positive IgG antibody test suggests past exposure and may indicate a prior infection which may be resolved or is still resolving, and/or protection against re-infection (“protective immunity”).
The SARS-CoV-2 antibody test has not been validated for purposes of diagnosis of infection or disease (COVID-19) and cannot be used to rule in or rule out infection or COVID-19. Sonora Quest offers the molecular test (test code 907080 for swab samples and 907078 for lower respiratory samples) for diagnosing an active COVID-19 infection.
IgG antibody testing should be performed to assess whether an individual (e.g., healthcare worker, student, general population, etc.) has been exposed to SARS-CoV-2 in the past. If a serology test delivers a positive result for the IgG antibody, that means the individual was previously exposed to SARS-CoV-2 and may indicate a prior infection which may be resolved or is still resolving, and/or protection against re-infection (“protective immunity”).
The Coronavirus COVID-19 SARS-CoV-2 Antibody IgG test is a qualitative test to detect IgG antibodies to the SARS-CoV-2 virus in your blood. The test code 907097 includes testing for the IgG antibody only and will provide insight into whether an individual has previously been exposed to the SARS-CoV-2 virus and may indicate a prior infection that may be resolved or is still resolving, and/or protection against re-infection (“protective immunity”).
The test name for IgG antibody testing is Coronavirus COVID-19 SARS-CoV-2 Antibody IgG. The test code is 907097.
Yes. In a letter issued on April 17, 2020, the US Food and Drug Administration (FDA) recommended that healthcare providers continue to use serological tests intended to detect antibodies to SARS-CoV-2 to help identify people who may have been exposed to the SARS-CoV-2 virus or have recovered from the COVID-19 infection. In its guidance, the FDA referenced that experience with other viruses suggests that individuals whose blood contains IgG antibodies associated with SARS-CoV-2 infection—provided they are recovered and not currently infected with the virus—may be able to resume work and other daily activities in society. They may also be eligible to serve as potential donors of convalescent plasma to aid in the treatment of those infected with COVID-19.
Our position at Sonora Quest is that antibody testing is an important tool in assessing potential risk and fostering a safer environment for all of us. We look forward to additional science to establish clearly the role of antibody testing in inferring immunity for COVID-19. Other respiratory illnesses, including SARS, a cousin coronavirus of COVID-19, has been shown to produce antibodies that can be assessed via lab testing to infer immune protection for a period of time. We encourage all individuals, regardless of their antibody response/test result, to continue to practice safety and health measures, such as social distancing, to further minimize risk.
The presence of IgG indicates prior exposure to SARs-CoV-2, a prior infection that may be resolved or is still resolving, and protection against reinfection (“protective immunity”). At this time, we have not established the duration of immunity. However, in previous viral outbreaks of SARS (SARS-CoV), IgG has been shown to provide immunity for up to 2 years. In most other viral diseases, IgG responses measurable by serological testing positively correlate with some level of protective immunity. An animal study of SARS-CoV-2 demonstrated protective immunity after infection. Early human studies demonstrate the development of protective/neutralizing antibody responses in individuals infected with SARS-CoV-2.
An equivocal IgG result may occur before an adequate antibody level has developed or maybe a cross-reaction. Retesting should be considered in 1-2 weeks if clinically indicated.
This suggests a person has not been exposed to SARS-CoV-2 or has been exposed very recently (antibodies have not yet been produced).
This suggests a person has not been exposed to SARS-CoV-2 or has been exposed very recently (antibodies have not yet been produced).
We will report the results qualitatively. There will be 3 results: Positive, Equivocal, and Negative. Each result will carry a comment consistent with the FDA guidelines. As the IgG test is used to detect prior exposure to the virus, and not to diagnose active infection, this test is not a Priority test and providers will not be contacted to discuss results. Providers should obtain results via standard processes.
The serological IgG assay that Sonora Quest offers is validated to be highly specific for SARS-CoV-2. For this validated assay, a positive result indicates a high likelihood of prior infection and that a person has mounted an immune response. Different assays target different viral proteins. Some assays detect antibodies to nucleocapsid and others detect spike proteins. Spike and nucleocapsid assays are highly correlated with each other. As additional research is conducted and vaccines potentially emerge, Sonora Quest will tailor SARS-CoV-2 testing offerings to be informed by evolving information.
In order to maximize our capacity and flexibility for testing in this time of need, Sonora Quest is utilizing technologies developed by EuroIMMUN to perform antibody testing for COVID-19.
Sonora Quest is implementing an immunoassay such as the enzyme-linked immunosorbent assay (ELISA). We perform our own validation using stringent acceptability criteria for precision, reproducibility, accuracy, method comparison, cross-reactivity, and clinical performance before starting patient testing. The accuracy of Sonora Quest’s SARS-CoV-2 serology testing performance characteristics is on par with other common virology antibody tests routinely performed at Sonora Quest (eg, Measles, Mumps, Rubella).
This test has been authorized by the FDA under Emergency Use Authorization (EUA) for use by authorized laboratories such as Sonora Quest.
We are defining “symptomatic” per CDC guidelines3: including (1) fever, measured as temperature > 100.3 °F, or subjective fever based on clinical judgment; and (2) respiratory symptoms, including cough, shortness of breath, and sore throat. Medical evaluation may be recommended for lower temperatures or other symptoms based on an assessment by public health authorities.
While there is a lot of uncertainty with this new virus, it is also possible that, over time, broad use of antibody tests and clinical follow-up will provide the medical community with more information about how safely someone who has recovered from the virus can be exposed to it again.
If you have IgG antibodies and you have symptoms, you likely have an active infection, you may infect others, and you may need to seek medical attention.
A positive IgG antibody test result suggests recent or prior infection with SARS-CoV-2. It usually takes at least 10 days after symptom onset for IgG detectable levels to be reached. Patients tested prior to this time may be negative for SARS-CoV-2 IgG antibodies. An IgG positive result may suggest an immune response to primary infection with SARS-CoV-2, but the relationship between IgG positivity and immunity to SARS-CoV-2 has not yet been firmly established. At this time, a positive IgG result has not been shown to indicate immunity, as such social distancing, also called “physical distancing,” should still be followed to assure that we continue to protect ourselves, our family, and our community.
A positive IgM and/or IgA test result, with a positive/negative IgG result, may indicate an active COVID-19 infection. A negative IgM and/or IgA antibody test result is likely to indicate that: (1) the person has not been infected with SARS-CoV-2 or (2) the person has been infected but there has not been enough time to produce an IgM and/or IgA response. Antibody tests have not been shown to definitively diagnose or exclude SARS-CoV-2 infection.
The presence of SARS-CoV-2 antibodies has been demonstrated in patients with undetectable viral RNA. Therefore, testing asymptomatic healthcare workers or patients with negative molecular diagnostic test results with antibody tests may add value in determining whether they have been exposed to SARS-CoV-2 or not.
This test has been authorized by the FDA under Emergency Use Authorization (EUA) for use by authorized laboratories such as Sonora Quest.
SARS-CoV-2 antibody tests are designed to detect specific antibodies against this virus. A positive IgG antibody test result suggests past exposure and may indicate a prior infection which may be resolved or is still resolving, and/or protection against re-infection (“protective immunity”).
A diagnosis, in general, is to rule in or to rule out the presence of a medical condition. Again, the SARS-CoV-2 antibody test cannot be used to rule in or rule out active COVID-19 infection.
To date, the United States Food and Drug Administration (FDA) has not required a review of information about any specific antibody test. The FDA is allowing laboratories to perform these tests without extensive review in response to the COVID-19 pandemic emergency.
It takes time to develop an immune response with the development of antibodies. Generally, most people form antibodies except those who are either immunocompromised or IgG deficient. Testing too soon will lead to a negative antibody test result. There is insufficient scientific information to understand the variation of timing and amount of antibody that develops to the SARS-CoV-2 virus that can be applied to all patients. Yet, we have experience with other viruses and can apply these learnings to SARS-CoV-2 until we know more.
Studies have begun measuring the seroconversion in SARS-CoV-2 patients. In one such study, 173 hospitalized patients in China, all patients (100%) developed antibodies against SARS-CoV-2.1 The median time to have detectable antibodies (called seroconversion) was 11 to 14 days, depending upon the type of immunoglobulin. (The median time is the number of days when 50% of those tested positive after the onset of symptoms.) 94% and 80% demonstrated seroconversion with IgM and IgG, respectively, by day 15 after the onset of symptoms. This study provides information from a small number of patients; larger studies are needed.
Findings from an antibody study of patients infected with a related virus to SARS-CoV-2 (namely the SARS-CoV outbreak in 2002-2003) demonstrated that among 176 patients who had severe acute respiratory syndrome, SARS-specific antibodies were maintained for an average of 2 years, and significant reduction of immunoglobulin G–positive percentage and titers occurred in the third year.2
There are three types of antibodies that can be measured: IgA, IgM, and IgG.
According to a recent white paper summary issued by the American Clinical Laboratory Association (ACLA), when used appropriately, antibody testing may help determine the number of individuals who have been infected with SARS-CoV-2. By supporting screening for individuals using serology, healthcare professionals can provide a more detailed assessment regarding the true rate of infection and gain a better understanding of the case fatality rate to help inform public health strategies. Serologic testing also potentially could be used to support future vaccine development and contact tracing (the process of identification of persons who may have come into contact with an infected person and subsequent collection of further information about these contacts) to stop the spread of the infection in the community.
Antibody testing measures the body’s immune response to an infection and can provide insights into an individual’s prior exposure to COVID-19 and may indicate a prior infection which may be resolved or is still resolving, and/or protection against re-infection (“protective immunity”).
Molecular PCR tests are used to directly detect the presence of the virus, rather than the presence of the body’s immune response, or antibodies. By detecting viral RNA, which will be present in the body before antibodies form, the molecular PCR tests can tell whether someone has the virus very early on and whether they are infectious. An antibody test tells us what proportion of the population has been infected. It won’t tell you who is infected, because the antibodies are generated after a week or two, after which time the virus should have been cleared from the system. But it tells you who has been infected and who is likely to be immune to the virus.
Yes, there are five primary classes of antibodies. Of those, IgG, IgM, and IgA are often used as part of infectious disease serology testing.
- IgG antibodies are found in all body fluids. They account for 75 to 80 percent of all antibodies. IgG antibodies are essential in fighting bacterial and viral infections, and when present indicate that someone has previously been exposed to a particular antigen and has developed an immune response. In general, these antibodies usually appear 10-14 days after symptom onset.
- IgM antibodies are found in blood and lymph fluid and are the first type of antibody made in response to an infection, usually detectable within 3-7 days from the start of the infection.
- IgA antibodies play a crucial role in the immune function of mucous membranes, such as the respiratory epithelium, but is also found in the blood. These antibodies also appear early in the infection process (3-7 days).
An antibody (also known as an immunoglobulin) is part of our body’s response to a foreign molecule or pathogen (also known as an antigen) such as a virus or bacterium. This is valuable to fight off infection. Protective antibodies can provide immunity so we do not become reinfected with the same viruses or bacteria. Antibodies are vital for our health.
Yet, we don’t always develop antibodies—or the right or sufficient antibodies—to fight off all infectious diseases. For example, people infected with HIV or hepatitis C virus do not usually develop protective antibodies.
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