Detection of IgG antibodies against the new coronavirus SARS-CoV-2, the virus that causes COVID-19, helps identify people who have been exposed to the virus. Serological results should not be used as a single laboratory test to diagnose or rule out a recent SARS-CoV-2 coronavirus infection.
This test is recommended for people at least 10 days after the onset of symptoms or after exposure to people with confirmed COVID-19.
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a virus with positive single-stranded RNA that causes coronavirus disease 2019 (COVID-19). Like other human coronaviruses, SARS-CoV-2 can cause infection of both the upper and lower respiratory system. Symptoms can range from mild (such as the common cold) to severe (such as pneumonia) in both healthy and immunocompromised patients. Transmission of the SARS-CoV-2 coronavirus occurs mainly through respiratory droplets. During the early stages of COVID-19, the symptoms may be nonspecific and look like other common respiratory infections, such as the flu.
The incubation period for COVID-19 ranges from 5 to 7 days. Usually, people with a normal immune system (immunocompetent) with COVID-19 disease show detectable IgG antibodies to SARS-CoV-2 about 8 to 11 days after the onset of symptoms. Patients screened before this time may be negative for IgG antibodies to SARS-CoV-2.
Negative results do not rule out SARS-CoV-2 infection, for example, if the sample is taken very soon after infection, in immunosuppressed patients or in some patients with mild disease. In these cases, molecular testing for SARS-CoV-2 coronavirus is recommended.
Positive results indicate current or past infection with the new SARS-CoV-2 coronavirus. The results of the antibody test should not be used as the sole test to diagnose or rule out SARS-CoV-2 infection. Sometimes the antibodies may be due to current or past infection with non-SARS-CoV-2 coronavirus strains, such as HKU1, NL63, OC43 or 229E coronaviruses.
Symptomatic patients should be screened with the molecular test.
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Last Updated: 05/05/2020