You can get a false negative on a sweat test, but not a false positive, so I imagine your center deemed it sufficient when your test came back positive. You can inquire about them testing for which genes you have though, if you like. I asked my doc just last year to test for my second one (I knew I had one DeltaF508 from testing when I was 5, but at that time, my other gene was too rare, and had no name), and it came back within a few weeks, and now I know. I think it's an interesting piece of information, but you don't really need it in your healthcare. At least not now. It's really up to you, whether or not you want to know.