Antibody tests like this are very limited. They only detect positive after you've had the virus for several days and they have a significant false negative rate. They are very poor at identifying if this person right here has the virus.

However if what you're doing is trying to assess the prevalence of the virus in a population of hundreds of thousands, or millions, they could be very useful. They will help identify clusters of infection so you can then use the PCR test on known associates to pinpoint cases.

I think this is what the Chinese government did in Beijing, they used mass antibody testing, but PCR testing of everyone in the food market where they knew there were cases.