Took the 'bullseye' with knee attached to the doctors back in 1989, sent test off iirc I think to Southampton where they were leading the way back then; test result came back 'negative', in the sense that according to the doc I had antibodies to it. Doc did say it was v hard to detect even when looking for it. I was aware of the symptoms and the warning bullseye rash, hence my turning myself in.
Apart from going doolally in my dotage, no ill effects to date, but many others have been much less fortunate.