I can add one data point to support this (not that it is worth much). I had the normal story of being sick in January in London with the "worst flu ever" and s

I can add one data point to support this (not that it is worth much). I had the normal story of being sick in January in London with the "worst flu ever" and suspected it might have been COVID. But I recently had a lab-based IgG antibody test and it came back negative. Everyone else in my family was also negative. Also, friends who have family members who work in the NHS with similar stories of being sick were also negative. No one I know directly has tested positive yet. I can't speak to the overall accuracy of the test, but the one I took was the private IgG antibody offered through the company 'Qured'.