Hello and welcome to HW! Like Chaser suggested, make sure the sweat tests were done at an accredited CF center. For more info on Ambry their website is www.ambrygen.com
. My son had the Genzyme test and then the full amplified Ambry test done, Steve at Ambry is very helpful!
There is also a Nasal Potential Difference test that can be performed (not every state has it), but I don't recommend it for children as it can be uncomfortable (so I am told).
Take care and I hope you find some answers...