Antibodies—this term has been all over the news lately. But what are they, how do they work and why do we need widespread antibody testing as part of a comprehensive diagnostic framework for the COVID-19 pandemic?
To better understand why antibody testing has become such a hot topic, we first need to understand the basics of immunity. Our Chief Medical Officer, Dr. Alan Wright, recently spoke with WebMD and Medscape for the organization’s Coronavirus in Context web series. In this discussion, Dr. Wright describes it in this way: “when a virus invades your body, it triggers an immune response. Part of this response includes the production of antibodies, which act like a “sticky note” on the invader that says, “kill me.” That signals our white blood cells to destroy the virus.”
When a virus first appears in a person, their body will initially generate antibodies that are unable to effectively attach to the virus and eliminate it. As a person’s immune response evolves, it will produce mature antibodies known as high-affinity antibodies that can attach to a virus and neutralize it. High affinity antibodies appear later in the course of the infection. These are the types of antibodies that effective antibody tests should aim to detect.
Antibody tests, which are not to be confused with the tests designed to detect if someone has an active infection, can be used to determine one’s immune response to a virus.
A good antibody test has high levels of sensitivity and specificity.
When considering the accuracy of antibody tests, having a high percentage of specificity matters more than the percentage of sensitivity because the greatest clinical risk lies in a patient believing that they have been exposed and developed an immune response to a virus when they actually have not.
It’s also important that antibody tests are designed in such a way that they don’t detect other antibodies from seasonal viruses such as the flu or the common cold. When this happens, a test can generate a false positive – falsely leading people to believe they have developed an immune response to SARS-CoV-2.
Roche’s lab-based antibody blood test has proven 100% accurate at detecting SARS-CoV-2 antibodies in the blood (sensitivity) 14 days post PCR, and 99.8% accurate at ruling out the presence of SARS-CoV-2 antibodies (specificity). The Elecsys® Anti-SARS-CoV-2 antibody test recently received Emergency Use Authorization from the United States Food & Drug Administration and is available on our cobas e analyzers, which are widely used in hospitals and labs around the world.
As we detail in a previous post, the information gleaned from an antibody test can help inform our “new normal” in many ways, which is why another important aspect of the antibody discussion centers around immunity and the possibility of re-infection. Considering that it is a completely novel pathogen, there are many unanswered questions about SARS-CoV-2 antibodies and the level of immunity they may provide. Dr. Wright notes that because of this, we don’t know yet whether antibodies provide protection against re-infection and for how long that may last. The scientific community is actively looking for answers to these questions.
To learn more about antibody testing, you can view Dr. Wright’s full interview here.
