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Antibody Testing for Covid- Not So Fast


                                                          Image from The Verge - Vox
I wrote a couple of weeks ago about the importance of having antibody testing for Corona Covid-19 as a pathway forward for resuming activity and work. Antibody tests are now being offered at urgent care clinics, private doctor offices, Labcorp labs and by the time you read this, there may be home antibody tests offered from ads online.

 I'm getting many requests a day from patients who think they had Covid if they had any illness from December onward.  "I want to know if it is Covid and if I am immune."   It is vitally important for us to know who has had the virus, who is immune from future exposure and who is safe for asymptomatic passing of the virus.  But...and this is a big BUT...antibody testing today is NOT READY FOR PRIME TIME.

Let's break this down.  Why?

The FDA has relaxed its usual standards and has permitted emergency use authorization for antibody testing.  This means Neighbor Joe can get some funding, throw some reagents together and develop an antibody test that may have no standards for reliability.  There are now over 90 tests on the market and we don't know if they work.  On May 4, the FDA acknowledged fraudulent tests and are requiring data showing accuracy within 10 days.  It is unknown how they can police all of the tests out there.

Robert Gallo, co-founder and director of the Institute of Human Virology says "I'm waiting for the ultimate good test".

For antibody testing to work in a disease that affects 2-3% of the population, we need a test with at least 99.7% specificity.  That means we need too know it is giving results for Covid-19 and not cross reacting with residual viral RNA from another Corona virus like the common cold.

Here is what we don't know about Covid-19:

  • We don't know at this time if the presence of antibodies to Covid-19 grants immunity or for how long. 
  • We don't know if a person can be reinfected
  • We don't know if serum therapy from patients who have had the virus can be given to very sick patients to help them recover with antibodies
  • We don't know how many false positive antibody results there are when we look at infection rates.
  • We don't know how many false negative antibody results there are when people had the virus but the test is negative.
  • We don't know if the formation of Covid antibodies varies by age. (In the common cold virus, people over age 60 form more antibodies). We don't know how many antibodies are optimal to have.

The FDA usually insists on rigor before they approve things.  As consumers and patients, we should appreciate these standards.  Otherwise we have the chaos that is plaguing us now and causing undue anxiety and confusion.

We need to give scientists the time to do their jobs and these questions will be answered.  Can we live with uncertainty?  Covid -19 is teaching us how.  We need to listen.

Comments

Anonymous said…
This is really good information. We keep being told that we need more testing and we need antibody testing. We are told everyone can have a test that wants one. Well that is not actually the case and it sounds like the tests aren't really reliable anyway. What a mess.

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