Advanced Diagnostic Laboratories

COVID-19 Spike Protein Semi-Quantitative IgG Antibody detection by ELISA, Serum (SQCOV)

Test Code

SQCOV

Description

Collect

Collect in a plain red top or SST tube.

Patient Prep

N/A

Pediatric Collection

Minimum Volume: 0.5mL serum

Unacceptable Conditions

Plasma, lipemic, grossly hemolyzed, microbially contaminated specimens, or specimens with visible particulates should not be used.

Storage Transport Temp

Preferred: Frozen Send serum Priority Overnight via FedEx and in a well insulated container on dry ice.

Also Acceptable: Refrigerated (2-8C) within 72 hours.

Stability

Up to 8 hours ambient or 72 hours refrigerated at 2-8°C. Freeze at or below -20°C for longer storage or shipping.

Notes

Novel coronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2, a single–stranded RNA coronavirus. Comparisons of the genetic sequences of this virus have shown similarities to SARS-CoV and bat coronaviruses. In humans, coronaviruses cause respiratory infections. Coronaviruses are composed of several proteins including the spike (S), envelope (E), membrane (M) and nucleocapsid (N). The spike protein binds to Angiotensin Converting Enzyme 2 (ACE 2) on cell surfaces and this binding is used by the virus as a mechanism of cell entry. Antibodies directed against spike protein may inhibit this binding and thus protect against viral infection and disease. IgG is the most abundantly found immunoglobulin to be produced in response to an antigen and will be maintained in the body after initial exposure or vaccination to provide a durable response.

The antibody test is a semi-quantitative ELISA that detects IgG antibodies to the spike protein of the SARS-CoV-2 virus. The test reports numerical results that may aid in evaluation of the antibody response over time. Concentrations of antibody are provided in relative (arbitrary) units (RU). Results from this test alone cannot be used to assume that protective immunity has been achieved against SARS-CoV-2.

Performed

Monday-Friday

Methodology

Semi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA)

Turnaround Time

5-10 Days

Department

Immunology Lab - Diagnostic

Synonyms

COVID, COVID-19, IgG spike protein antibody

Study Offerings

RUO
CAP/CLIA

Ordering Recommendations

N/A

Reference Interval

	RU/mL*
Negative	<8
Borderline	>=8 to < 11
Positive	>= 11

RU: relative units

Interpretation

NEGATIVE. Negative results for IgG antibodies do not rule out SARS-CoV-2 infection. In the first week of the onset of the infection, the IgG response may be negative or of low level. Following vaccination with a SARS-CoV-2 vaccine, IgG antibodies may start to appear at approximately 7 to 21 days. It is not yet known how long IgG antibodies may persist following infection or vaccination. In addition, patients with low immunity or other diseases that affect immune function, failure of important systemic organs, and use of drugs that suppress immune function can also lead to negative results for IgG antibodies to SARS-CoV-2. The amount of antibodies may be below the detection level of the assay.

BORDERLINE. Borderline result indicates the detection of IgG antibodies, but it did not meet the threshold for positivity. This may indicate cross reactivity or very early infection or if immunized with a vaccine containing the viral spike protein, it may indicate that the time at which blood was drawn was too early or too late to detect IgG antibodies. Repeat collection recommended.

POSITIVE. A positive test indicates that there are IgG antibodies present in the patient's sera suggesting a past infection or a response to vaccination with a SARS-CoV-2 vaccine containing the spike protein. A positive result cannot be used to assume that protective immunity has been achieved against SARS-CoV-2.