Regarding this, I was on another site for physicians, and the question came up if they were being tested by either PCR, rapid molecular testing, or antibody testing. Most are in large organizations that have mandated protocols to follow regarding testing. It was interesting to see how the policies were all over the chart, from no testing if asymptomatic, to twice weekly swabs, and occ. antibody tests.
The consensus was that antibody tests were useless for the individual, and helpful only in the long run to researchers. The results are highly dependent on the subgroup you are testing. If you are doing antibody testing of people who had confirmed PCR positive disease, it is pretty indicative of an immune response. However, a fair number of folks turn negative for antibodies in a couple of months, making it a poor indicator of past infection, and of course leading to questions as to how long lasting immunity will be. If done in mass screening of people who are not known to have disease, a large percentage of the positives will be false positives, again making interpretation of results problematic. That is why we have epidemiologists, I suppose, who have to training and knowledge to ultimately tease something meaningful out of the raw data.