In an effort to help gain a better understanding of individuals having contracted COVID-19, the US Food and Drug Administration (FDA) has granted the first Emergency Use Authorization (EUA) for a serology test to Cellex, Inc., a North Carolina-based company. The test will only be authorized for use in laboratories proficient enough to conduct moderate and high complexity tests, and will provide results in 15 minutes.
The test will be capable of detecting the antibodies – immunoglobulin M (IgM) and immunoglobulin G (IgG) – produced by the human immune system in response to SARS-CoV-2, the virus that causes COVID-19. Despite recommendations from the FDA that results from the serology test should not be made the only diagnostic or exclusion criteria for a coronavirus infection, the test can make it easier to detect the number of people who have had a SARS-CoV-2 infection but remained asymptomatic.
Identification of Antibodies Helps Detect Infection
The FDA grants an Emergency Use Authorization (EUA) with the understanding of a few key elements. First, the SARS-CoV-2 can cause serious, life-threatening conditions, such as severe respiratory disease to humans. Second, and based on scientific evidence available, the FDA has reason to believe that the sanctioned tests will be effective in diagnosing COVID-19, and that their potential benefits outweigh any risks. Lastly, there is currently no approved and adequate test available as an alternative to the test/s being authorized.
Dave Hickey, president of Integrated Diagnostic Solutions for Becton, Dickinson and Company, a company also involved in producing a diagnostic test for COVID-19, explains:
Serology tests are important because they provide an additional piece of information to aid in characterizing possible prior exposure to SARS-CoV-2, especially since many infections are mild or asymptomatic in severity. Initial evidence suggests that nearly all patients infected with SARS-CoV-2 will have developed a detectable antibody response within days of symptom onset, at which time a negative serologic test, along with molecular diagnostics, could be helpful in ruling out COVID-19.
The FDA explained in the EAU:
IgM antibodies to SARS-CoV-2 are generally detectable in blood several days after initial infection, although levels over the course of infection are not well characterized. IgG antibodies to SARS-CoV-2 become detectable later following infection. Positive results for both IgG and IgM could occur after infection and can be indicative of acute or recent infection.
Immunoglobulin M (IgM) is generated as the first line of defense during a viral infection followed by the production of adaptive, high-affinity immunoglobulin G (IgG) responses that provide long-term immunity via immunological memory. These antibodies are usually present in the middle to later stages of an infection, but may persist after exposure. This helps clinicians identify individuals who have been exposed to the novel coronavirus even if they showed no symptoms of the disease.
However, the FDA has also stated that it is still unknown how long IgG and IgM antibodies remain in the body after an infection, and whether or not they confer immunity to the virus. Nevertheless, data on past exposure is significant for research scientists and epidemiologists to more effectively understand the likelihood of occurrence of COVID-19 within a population. Information in this regard will play a key role in formulating strategies for combating any future COVID-19 outbreaks.