April 10, 2020

expert comment on antibody tests and population surveillance for COVID-19

Comment on antibody tests and population surveillance for COVID-19.

Prof Sheila Bird, Formerly Programme Leader, MRC Biostatistics Unit, University of Cambridge, said:

“To get an idea of how many of us in the population (healthcare workers, pregnant women, children, those aged 70+ years) have been exposed to the virus, we need an antibody test to be able to assess that.  When it comes to being very sure that someone has definitely had the virus and still has antibodies to it, we need a very good and reliable antibody test to be able to do that too – this is the ‘have-you-had-it’ test we hear about.

“Knowing how many of us have been exposed to the virus is important for being able to calculate accurately the death rate of this virus amongst all who were infected (not just among those severely enough affected to have tested COVID-positive in the PCR ‘have-you-got-it’ test).  As importantly, the proportion of the population who still have antibodies and – we hope – immunity, has implications for what the future of the epidemic might look like.

“Getting robust estimates of the proportion that have already been exposed to COVID-19 helps inform our knowledge and future planning.  And in my opinion this might be easier to achieve than developing a very specific and sensitive test for the purposes of finding out who definitely maintains immunity to it.  Why?  Because we can make do with a less well-performing antibody test for the purpose of population surveillance – because we can take account statistically of its weaker performance.  This has been done before in surveillance studies: both for HIV and hepatitis C virus (HCV).  But, of course, we still need a very very good COVID-19 antibody test to be able to tell individuals they are safe to go back to work.  We need both.  But history and statistics remind us that a weaker test may still deliver for surveillance!”

All our previous output on this subject can be seen at this weblink:

www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.