Posted by dan on April 3, 2020, 4:24 pm, in reply to "Question for Dan"
IgG antibody doesn't go up immediately with infection so may not be useful to make diagnosis during infection.
Classically to identify atypical respiratory infection when I was a boy we used to take sera acutely in hospital and then convalescent sera at 6 weeks in outpatient department to see which antibody levels had changed.
An antibody test could be used as surveillance to test the proportion of people in a population who had had the infection. Could also be used as confirmation of immunity as part of a certification process - though that will drive people into exposing themselves.
Free availability of the PCR test is the way forward.