TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: CVNFS    
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibody, Follow up, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Identification of convalescent plasma donors after confirmation of past severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection

 

Documenting adaptive immune responses in those undergoing SARS-CoV-2 vaccination

 

This test should not be used to exclude active or recent SARS-CoV-2 infection.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If the neutralizing antibody (NAb) assay is positive, then the NAb titer is performed at additional charge.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a positive-sense, single-stranded RNA virus that causes coronavirus disease 2019 (COVID-19). Like other coronaviruses that infect humans, SARS-CoV-2 can cause both upper and lower respiratory tract infection. Symptoms can range from mild (ie, the common cold) to severe (ie, pneumonia) in both healthy and immunocompromised patients. SARS-CoV-2 transmission occurs primarily via respiratory droplets. During the early stages of COVID-19, symptoms maybe nonspecific and resemble other common respiratory tract infections, such as influenza.

 

The incubation period for COVID-19 ranges from 5 to 7 days. Typically, immunocompetent individuals with COVID-19 develop detectable antibodies against SARS-CoV-2 approximately 8 to 11 days following onset of symptoms. Some of these antibodies have the capacity to directly neutralize or block SARS-CoV-2 infection and are thus considered neutralizing antibodies (NAb). Standard serological tests used to detect antibodies to the SARS-CoV-2 do not differentiate between neutralizing and non-neutralizing (eg,, binding) antibodies. Rather, direct measurement of the ability of antibodies to block the infection of live replication-competent virus is considered the gold-standard method for measurement of NAb.

 

Convalescent plasma therapy in increasingly being utilized as a treatment for severe cases of COVID-19. The success of convalescent plasma infusion has been previously demonstrated to correlate with the titers of NAb for other viruses (i.e., SARS-CoV, influenza).  There is notable variation in the titer of NAb across convalescent plasma donors upon recovery from COVID-19 and therefore prescreening individuals is recommended. Currently the FDA recommends a NAb titer of 1:160 for convalescent plasma donors.

 

The titer of NAb post vaccination is also used to evaluate efficacy of a vaccine.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

Interpretation Provides information to assist in interpretation of the test results

Negative Screen:

No neutralizing antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detected. Not all patients infected with SARS-CoV-2 will develop neutralizing antibodies including those with positive serology. Negative results may occur in specimens collected too soon following infection, in immunosuppressed patients, or in some individuals with prior mild illness. Repeat testing may be helpful in patients tested less than 14 days after symptom onset.

 

Positive Titer (with Positive Screen):

Neutralizing antibodies against SARS-CoV-2 detected. This result does not indicate immunity to SARS-CoV-2.The duration and durability of neutralizing antibodies following seroconversion is unknown. Based on these results the patient may be eligible to be a convalescent plasma donor. For more information visit https://thefightisinus.org/en-us#home.

 

Negative Titer (with Positive Screen):

No significant level of neutralizing antibodies to SARS-CoV-2 was detected. Not all patients infected with SARS-CoV-2 will develop neutralizing antibodies including those with positive serology. Negative results may occur in specimens collected too soon following infection, in immunosuppressed patients, or in some individuals with prior mild illness. Repeat testing may be helpful in patients tested less than 14 days after symptom onset.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Negative results do not exclude prior severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. If an acute infection is suspected, direct testing for SARS-CoV-2 is necessary.

 

False-positive results from the SARS-CoV-2 neutralizing antibody test may occur due to cross-reactivity from pre-existing antibodies or the presence of other interfering substances.

A NAb titer associated with protective immunity has not yet been established. Also, the duration and durability of NAbs against SARS-CoV-2 is unknown.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1 Wu F, Wang A, Liu M, et al: Neutralizing antibody responses to SARS-CoV-2 in a COVID-19 recovered patient cohort and their implications. medRxiv. 04/20/2020. doi: h10.1101/2020.03.30.20047365. Available at www.medrxiv.org/content/10.1101/2020.03.30.20047365v2

2. Ju B, Zhang Q, Ge J, et al: Human neutralizing antibodies elicited by SARS-CoV-2 infection. [published online ahead of print 2020 May 26] Nature. 2020 May 26. doi: 10.1038/s41586-020-2380-z

3. Jiang S, Hillyer C, Du L: Neutralizing antibodies against SARS-CoV-2 and other human coronaviruses. Trends Immunol. 2020 Jun;41(5):355-359

4. Vandergaast R, Carey T, Reiter S, et al: Development and validation of IMMUNO-COV: a high-throughput clinical assay for detecting antibodies that neutralize SARS-CoV-2. bioRxiv. 2020 May 27;2020.05.26.117549. doi: 10.1101/2020.05.26.117549. Available at www.biorxiv.org/content/10.1101/2020.05.26.117549v1

5. Case JB, Rothlauf PW, Chen RE, et al: Neutralizing antibody and soluble ACE2 inhibition of a replication-competent VSV-SARS-CoV-2 and a clinical isolate of SARS-CoV-2. bioRxiv. 2020 May 18;2020.05.18.102038. doi: 10.1101/2020.05.18.102038 Available at www.biorxiv.org/content/10.1101/2020.05.18.102038v1

6. Duan K, Liu B, Li C, et al: Effectiveness of convalescent plasma therapy in severe COVID-19 patients. Proc Natl Acad Sci USA. 2020;117(17):9490-9496