Not All Equal

Governors of every state are demanding more antibody testing to help them make critical decisions on when and how to open their state economies.  It would be a worthy goal to test every American in the next several months.  This would help determine how widespread the COVID-19 infection is and what percentage of the population might already be immune.  It should come as no surprise that antibody testing done to date estimates that 15% of New York State residents are positive for antibodies.  This would suggest that the number of infections in the state were higher than detected.  Officials believe that some individuals who were infected either had no symptoms or their symptoms were so mild as to be largely ignored.  The number of positive antibody tests in Los Angeles County, on the other hand, was only 4%.  Does that mean the infection rate is lower in California than New York or are we looking at a large number of false negative tests.  Some have questioned the validity of test kits since we are still dependent on foreign suppliers of much of our testing materials.  Poor quality testing materials are more likely to produce a false negative result.  The limiting factor to widespread testing is the production and distribution of reliable testing materials.  Foreign producers may not follow the same quality standards as American companies.  I think this unfortunate pandemic has taught us that we should not be dependent on foreign nations for critical supplies like PPE, laboratory tests and (most importantly) pharmaceuticals.  A cheaper price often brings an inferior product and when it comes to medical care, lives may be at stake.  Economies can gradually resume activities with adherence to social distancing and other prescribed practices by health authorities.  Testing will determine who is immune and can safely move about in society and even volunteer to care for COVID-19 patients.  They could also serve as plasma donors since that appears to be a proven therapy for the sickest COVID-19 patients.

It is disturbing to hear reports of patients who recovered from a COVID-19 infection but were subsequently re-infected.  Dr. Birx and others have been informing the public that a “positive” antibody test does not guarantee immunity and there remains a potential for re-infection.  In a previous blog I described the difference between short-term antibodies and long-term or “memory” antibodies.  Perhaps individuals re-infected have not formed the long-term antibodies capable of providing lifetime immunity.  Another explanation could be that the patient’s antibodies are in numbers too low to be protective.  The antibody level in the blood is known as the “titer” and the higher the “titer” the greater the protection.  It is a known fact that antibody levels decrease over time, but that takes many years (often decades).   Not enough time has passed for antibody levels to have fallen significantly.  Any antibody tests must be comprehensive enough to tell us the following: 1) presence of IgM antibody = acute infection, 2) presence of IgG antibody = past (cured) infection, 3) IgG antibody titer = level of immunity.   A simple positive antibody test can help the epidemiologists but it doesn’t help us understand those who pose no threat to others.  We will gain a wealth of information from antibody testing and should focus on that rather than testing for the virus.  Viral testing is useful in establishing the number of new cases, but antibody testing provides the better overview of where we are in the infection cycle.

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