The Role & Benefits of COVID-19 Antibody (IgM & IgG) Testing
SARS-CoV-2 (COVID-19) Background
The average incubation period for the novel coronavirus is 5 to 6 days from exposure to infection, ranging between 2 to 14 days depending on the individual. Once infected, you may experience symptoms (symptomatic) or not (asymptomatic). If you are asymptomatic, you would never know if you were infected and a possible carrier of the disease unless tested.
If you do develop symptoms, they typically will manifest within 3 to 5 day post-infection, on average. Some hallmark symptoms associated with the infection include fever (88%), dry cough (68%), fatigue (38%) and coughing up of thick phlegm from the lungs (33%). If you are symptomatic, you can be contagious up to several weeks once infected. However, if you are asymptomatic, the average period of being contagious is 8-10 days. This is all determined by your body’s ability (or inability) to manage the disease.
Testing Options
Three options exist for COVID-19 testing. One looks for the virus itself on a molecular RNA level (PCR) and another tests for the actual viral protein know as an antigen test. Both use a nasal swab to collect the sample. The third looks for two antibodies (IgM and IgG) in your blood that are developed by your immune system in response to the presence of the virus.
PCR Testing
PCR is extremely sensitive in detecting COVID-19 RNA. However, PCR cannot differentiate between infectious and non-infectious COVID-19; the latter of which still has RNA that can exist for days-to-weeks after you are no longer infected. PCR also generates high false negative (FN) results ranging from 100%-67% during the 1st four days of the infection, and then drops to 38% by day 5. By day 8 FN are still at 20%, back up to 38% by day 14, and rises again to 66% by day 21. On the flipside, here in AZ, PCR generates a 8-10% false positive (FP) results. What does this mean? As an example, if you have a disease prevalence of 2% with a FP test rate of 10%, for every 100 individuals tested 12 will test positive for COVID-19…. but only 2 of those 12 will have it.
IgM and IgG Antibodies
These two COVID-19 antibodies ONLY develop in response to the presence of the virus Their synergistic roles are to attack the virus and remove it from your body. Except for immunodeficient patients, IgM can be detected as early as 3-days after infection and provides the first line of defense in attacking the virus. IgG development is initiated an average of 7-10 days later and is a very powerful 2nd line of defense. It not only works with IgM to combat and remove the virus, but it also plays a key role in your body’s ability to build up some level of longer-term immunity to the virus in the future.
Using IgM and IgG test results, coupled with a timed-interval or virus symptom driven testing strategy, Beacon can provide “actionable” data that PCR cannot as exemplified by the following four (4) possible outcomes:
Both IgM and IgG are Negative: Your immune system does not recognize you as being infected with COVID-19. You may still be in the incubation period, or you may be post-infection and the antibodies returned to baseline. Additionally, you are not immune to getting infected in the future.
IgM is Positive but IgG is Negative: You are potentially in an early phase COVID-19 infection.
Both IgM and IgG are Positive: Your immune system is engaged in an active COVID-19 infection.
IgM is Negative but IgG is Positive: You had recently been infected and now are developing (or have develop) some level of immunity.*
*While your immune system may develop some level of functional immunity to this virus once it has been eliminated, it is important to note that the extent and duration of any immunity is still unknown and can vary from individual to individual.
Time Critical Delivery of Data
Finally, when it comes to the value of test data in helping develop a back-to-work and/or a quarantine strategy, that objective is significantly diminished (if not eliminated) if it takes several days or weeks to get test results back from the lab. Beacon can provide “actionable” COVID-19 IgM and IgG antibody test results within 24-hours of sample receipt.
1. Kucirka, Lauren (MD, PhD) et al; Variation in False-Negative Rate of Reverse Transcriptase Polymerase Chain Reaction–Based SARS-CoV-2 Tests by Time Since Exposure; Ann Intern Med. doi:10.7326/M20-1495
2. ..\Inspire Health Alliance\Articles\False Positives in rt-PCR Testing for SARS-CoV-2 (COVID-19).A Cohen et May 20 2020_NH_MedRxiv.pdf