Hi Cyn,
I had MELISA do my test and I wasn't aware that other labs could or would be able to do it.... I mean MELISA.org of course.
It is fact that your sensitivity can go up after you have had metallic prosthetics implanted too... you body can react after the event. Also, it makes sense that you have had reactions to some things on your skin which came up as negative or low on the test, and vice versa in fact. It is due to our external tissues being a very different contact environment to something internal.
Just thought i'd throw this out there for you