The SARS-CoV-2 virus is a novel virus that causes the 2019 coronavirus disease (COVID-19) that is of global health significance. SARS-CoV-2 is believed to spread by respiratory droplets from an infected individual in close contact. Several methods are used to detect the SARS-CoV-2 virus. These methods include detecting the virus genome directly, for example by PCR, or by detecting antibodies produced as the body fights the virus.
An antibody test detects the presence of antibodies, which are specific proteins made in response to infections. Antibodies are detected in the blood of people that are tested after an infection. Antibodies show an immune response to an infection. Antibody test results are especially important for detecting previous infection in people who had few or no symptoms.
Accurate interpretation of serology testing depends on antigen specificity, but also on the type of antibody being detected. Humans have five different classes of antibodies, with each playing a unique role in immunity. IgM, IgG, IgA, and total antibody detection are the primary targets of serology tests for COVID-19.
Antibody test results should not be used to diagnose someone with an active SARS-CoV-2 infection. It typically takes 1 to 3 weeks after infection with SARS-CoV-2 for antibodies to develop, with some people it may take even longer to develop antibodies. Depending on when someone was infected with the virus and the timing of when the test was performed, serology tests may not detect antibodies in someone with an active infection. A test that detects the SARs-CoV-2 virus directly in respiratory samples may be used to diagnose active infections.
We do not know if the antibodies that result from SARS-CoV-2 infection will provide an individual with protection (immunity) from being infected again by the virus. If antibodies are found to provide immunity, it is not known how much antibody will provide protection or how long the protection may last.
-excerpts from the Centers for Disease Control and American Society of Microbiology
“Simply put, the COVID-19 serology blood test tells you if you have been exposed. Not all patients that are exposed show symptoms of disease. Serology tests for IgG begin to exhibit positive results on average 14 or more days after infection or exposure to SARS-CoV-2. Furthermore, tests for IgM and, the more sensitive, IgA antibodies can be useful for detection of exposure earlier than IgG antibodies. Generally, these antibody tests may exhibit a positive result as early as 4 to 14 days after exposure. Serology tests are useful in helping healthcare providers assess the risk of spread, in disease surveillance, and for determining risk of exposure. A positive serology result does not eliminate the possibility of a patient having an existing and active COVID-19 infection. It is possible, a small number of patients may generate antibodies, become sero-positive, and be in a ‘carrier state’ – able to transmit the virus. Remember the gold standard test for SARS-CoV-2 infection is PCR tests. Please see your healthcare professional for advice regarding testing and result interpretation.
Fry Laboratories, LLC has researched the best available serology for test. These tests are Emergency Use Authorized by the FDA. It is our commitment to provide the best and most accurate results in a timely manner for our patients and client healthcare providers.”
-Stephen E. Fry, M.D., Founder and Medical Director, Fry Laboratories, LLC, May, 2020