Reference Interval
IgG antibodies to SARS-CoV-2 NOT DETECTED
IgG antibodies to SARS-CoV-2 BORDERLINE
IgG antibodies to SARS-CoV-2 DETECTED
Interpretive Data
This antibody test for SARS-CoV-2 is an ELISA that detects IgG antibodies to the spike protein of the SARS-CoV-2 virus.
The United States (U.S.) Food and Drug Administration (FDA) has made this test available under an emergency access mechanism called an Emergency Use Authorization (EUA). The EUA is supported by the Secretary of Health and Human Service's declaration that circumstances exist to justify the emergency use of in vitro diagnostics for the detection and/or diagnosis of the virus that causes COVID-19. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes. Validation of assay performance was carried out at National Jewish Health. Testing is limited to National Jewish Health laboratories that are CLIA and 42 U.S.C. 263a certified high-complexity laboratories. FDA is not aware of an antibody test that has been validated for diagnosis of SARS-CoV-2 infection.
Test results from antibody testing should not be used as the sole basis to diagnose or exclude SARS-CoV-2 infection or to inform infection status. In addition, results from this test alone cannot be used to assume that protective immunity has been achieved against SARS-CoV-2.
NOT DETECTED. 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.
DETECTED. 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. However, a positive result does not rule out a past or present infection with non-SARS-CoV-2 coronavirus strains, such as coronavirus HKU1, NL63, OC43, or 229E. A positive result cannot be used to assume that protective immunity has been achieved against SARS-CoV-2.