Re: question about sweat test
I guess for piece of mind, I'd push for a genetic blood test -- ambry or qwest. These test for hundreds of gene mutations. DS was one of those who had a normal sweat test at an accreditted CF facility -- his was a normal 32; however, because of other symptoms, loose stools, bowel obstruction, they did a blood test, which BTW was sent to Mayo. He tested positive for CF.
There are several genetic mutations of CF with little if no symptoms. Some people have sinus issue, some more related to digestion. I've heard of someone whose daughter was diagnosed thru newborn screening and they went back and tested an older child who'd never even had an ear infection -- she too tested positive for CF.