SARS-CoV-2 Antibody (Serologic) Testing

Information for Healthcare Professionals

First-line testing for acutely ill patients remains the SARS-CoV-2 PCR

There are now two types of tests that can be used to evaluate patients and caregivers for SARS-CoV-2. The test most are familiar with is the PCR-based test that we have been using since March; this test is used to detect acute infection in patients that have symptoms of COVID-19. The PCR test is performed in testing centers and drive-through sites. It detects the virus in the patient’s upper respiratory tract via a nasopharyngeal swab.

This test is often positive early in the course of a patient’s active infection. How long the virus remains in the nasal cavity is an area of active study. In some patients the virus can remain detectable in the nasal cavity for an extended duration despite complete clinical recovery while in others the virus may become undetectable after 7 days. If the test is positive, it means the patient is currently infected with the virus and can potentially transmit the virus to other people. Occasionally, patients can be asymptomatic and still have virus detected in their upper respiratory tract.

The PCR test should be the first-line test for all patients and caregivers with active signs and symptoms of COVID-19.

SARS-CoV-2 antibody (serologic) test now available

The new SARS-CoV-2 test is an antibody test, or serologic test. This test is a blood-based test and detects a patient’s antibody response to SARS-CoV-2 infection. The tests have a turnaround time of approximately 48 hours.

The primary objective of SARS COV-2 antibody testing is to assess whether an individual has been previously infected with SARS-CoV-2. Generally, patients start to develop detectable antibodies 7-14 days after their symptoms have started. The test cannot differentiate very recent infection from more remote infection.

However, we do not yet know if the presence of antibodies to SARS-CoV-2 provides any level of protection against re-infection with the virus. Studies on SARS-CoV-2 have shown that a patient can also develop antibodies while remaining positive on nasopharyngeal PCR testing.

How will we use the new antibody test?

The role of antibody tests in the diagnosis of acute or previous SARS-CoV-2 infection is subject to change given the rapidly evolving science of SARS-CoV-2 infection. Results of antibody testing should not be used as the sole basis to either diagnose acute infection or make recommendations on limiting social or environmental exposures or changes to work related policies.

Intermountain will prioritize antibody testing in patients where a positive result will be actionable. Antibody testing will be prioritized in the following manner:

First Priority Category:

The viral load in the upper respiratory tract in patients with COVID-19 begins to fall early in the disease course while SARS-CoV-2 antibodies are often detectable 8-14 days after symptom onset. If nasal PCR testing is performed after 8 days of symptoms, it may be negative due to decreased viral shedding and an antibody test may be helpful in diagnosing acute infection.

As such, hospitalized patients with signs and symptoms of COVID-19 for at least 8 days AND a negative nasal PCR test will be prioritized for testing. Outpatients with active signs and symptoms of COVID 19 for more than 14 days will also be prioritized for testing. If the initial serology test is negative, repeat the test in 7 days if clinical suspicion remains high. View below an example of a completed inpatient and a completed outpatient iCentra PowerForm representing these scenarios.

A paper order may also be used to order serology testing.  Use the SARS-CoV-2 (COVID-19) IgG Serology Patient History Form to document the patient’s screening criteria.  This form must be submitted to the Intermountain lab for the testing to be completed.   


Example of a completed inpatient PowerForm:

inpatient powerform


Example of a completed outpatient PowerForm:

outpatient powerform

Please keep in mind: results of antibody testing should not be used to guide recommendations on social or environmental exposures or changes to work-related policies.

Second Priority Categories:

Asymptomatic patients and healthcare workers with high-risk, unprotected exposures to known COVID-19 patients also qualify for testing. To ensure adequate time has elapsed since exposure for antibody development, testing should not be performed in the first 14 days after exposure. It is preferable to wait 21 days from exposure to assess for antibody development. A household contact of a COVID-19-infected patient is an example of an asymptomatic, high-risk exposure. Intermountain caregivers with a high-risk, unprotected COVID-19 exposure are asked to contact ASK HR immediately after the exposure to discuss testing with Employee Health.

View below for an example of a completed PowerForm for an asymptomatic, exposed patient and for a completed PowerForm for an asymptomatic, exposed healthcare worker. Routine screening of asymptomatic, unexposed healthcare workers for SARS-COV-2 antibodies is not recommended at this time.


Example of a completed asymptomatic, exposed patient PowerForm:

asymptomatic exposed powerform


Example of an asymptomatic, exposed healthcare worker PowerForm (to be completed by Employee Health only):

asymptomatic exposed healthcare w powerform

Patients or healthcare workers who had a respiratory tract infection consistent with COVID-19 after December 1, 2019 that was previously undiagnosed qualify for testing in this second category as well if, in the opinion of the ordering clinician, it will alter clinical management of the tested individual.

Please keep in mind, results of antibody testing should not be used to guide recommendations on social or environmental exposures or changes to work-related policies. Individuals must have resolution of respiratory tract symptoms for at least 14 days prior to serology testing.


Example of a completed previous, consistent-COVID-19 syndrome PowerForm:

consistent w covid resp powerform


Population-based studies of asymptomatic persons to evaluate disease prevalence and PPE efficacy in a coordinated and structured manner would be performed in consultation with the Utah Department of Health, the Centers for Disease Control and Prevention, Intermountain’s Infectious Diseases and Epidemiology Division, and Intermountain Researchers. Please do not order antibody tests for this indication.

Please keep in mind: results of antibody testing should not be used to guide recommendations on social or environmental exposures or changes to work-related policies.

What a positive test means:

  • Demonstrates likely prior infection with SARS COV-2.
  • The body has produced a measurable antibody response to SARS COV-2.
  • In some cases, a positive test can represent a “false positive”, especially in individuals without a history of a COVID like syndrome.

CAUTION!

  • A positive test should not provide assurance that a patient is immune to SARS-CoV-2. A positive test means a person was infected with SARS-CoV-2 and their immune system has reacted to it. At this point, we do not know if a positive antibody test provides any protective immunity against repeat SARS-CoV-2 infection.
  • A positive test does not mean a caregiver can work without PPE or with modified PPE.
  • A positive antibody test in someone that still has symptoms does not mean that SARS-CoV-2 is no longer active or spreadable to others.
  • A positive test does not allow normal movement in the community without masking.
  • A positive test does not say where the infection occurred (i.e., the community or in a healthcare setting).
  • A positive test does not imply PPE failure. A caregiver is also a member of the community with exposures to family members, grocery stores, and other community members. A positive test could indicate an infection acquired in your community.

What a negative test means:

  • No evidence of prior SARS-CoV-2 infection. However, if symptoms have only been present for less than 14 days it may be too early for the body to have mounted a detectable antibody response.
  • Cannot be used to rule out acute or asymptomatic infection. It is unclear if asymptomatically infected individuals mount an immune response with a detectable antibody.
  • Immunocompromised individuals may not create adequate or detectable antibody response.

Frequently Asked Questions

If I have had a high risk, unprotected exposure to a COVID 19 patient, how do I get an antibody test ordered?

  • Immediately after the high-risk exposure call ASK HR at 801-442-7547 or email them at ASKHR@imail.org to discuss the exposure with Employee Health. Then:
    • An Employee Health nurse will talk with you and take down your information and exposure details
    • The Employee Health nurse will inform you that you have been placed on an antibody testing list
    • Infectious Disease physicians regularly review this antibody testing list to prioritize tests (from our limited test capacity) for those individuals whose care and treatment decisions would benefit from knowing the results of this test
    • You will be notified within 5 business days when your order will be placed
  • Your primary care provider can also order an antibody test if you meet the above criteria.

How do I order the SARS-CoV-2 antibody test for a patient?

Where can a patient be tested for SARS-CoV-2 antibodies? 

  • Symptomatic Patients:  Patient should wear a surgical/procedure mask.  Phlebotomist should use droplet and contact precaution PPE (eye protection, mask, gown, gloves). 
    • Blood may be collected in provider office 
    • Patient may be sent to an Intermountain Medical Group Clinic that performs drive-through phlebotomy (have the patient call before arriving to ensure the phlebotomist can don appropriate PPE). 
  • Asymptomatic Patients: Patient should wear a cloth or surgical/procedure mask.  Phlebotomist should use standard droplet precaution PPE (eye protection, mask). 
    • Blood may be collected in provider office 
    • Patient may be sent to any Intermountain lab collection site 

How are positive tests reported to the state health department?

  • Positive tests will be routed to the state health department from ARUP or Intermountain Central Lab.
  • Negative tests will not be routed to the state health department.

How will I be notified of antibody results?

  • Results of antibody tests will be routed back to the ordering provider via usual lab communication.
  • Positive results will not be called directly to the ordering clinician.
  • The COVID remote patient monitoring program will NOT be monitoring results.

Will the COVID Call Center order SARS-CoV-2 antibody tests?

  • No. Patients calling with requests for an antibody test will be referred to primary care.