Emily had two, both extremely high, and one mutation on the Ambry test.
Shawn is more like your daughter. He had one mutation on the Ambry test. He had 'borderline' symptoms to match his borderline sweat test results- asthma, sinusitis, but a normal CF sputum culture and a normal chest xray despite bad pft's. (in other words, more consistent with asthma rather than cf.) We had to go on to other testing to figure things out. Eventually NPD testing came back normal. He's now considered a symptomatic carrier. After all of what we ended up having to do to rule him a carrier, I wish the 30 came first which maybe would have saved me a whole lot of worry, but that wasn't the case- we were presented with the 48 & 54 first and had to follow through. But in our case we could see just how changeable sweat tests were. They were NOT a good indicator of whether or not he had CF, and yet was very definitive for his sister, who tested at over 100.
No ONE test for this disease, taken in isolation, can completely rule out CF. Some can rule it in with 100% certainty (i.e. genetic test finding 2 known disease-causing mutations), but nothing can rule it out with 100% certainty. Everything needs to be looked at together: sweat test results, newborn screen, genetic test results, family hx, symptoms, response to cf-specific treatment, test results like sputum culture, xrays/ct scan, etc. Only then can an accurate dx be made.
What symptoms does she have? That, really, is just as important in determining dx as what the results of another sweat test would be.
I'd also strongly recommend finding a center where you could get NPD testing for her. It won't be illuminating for everyone, but can be very helpful. <img src="i/expressions/face-icon-small-smile.gif" border="0"> They do it at Hopkins, CHOP(where they are doing a research study- that is where I took Shawn and it was worth the travel to get there), I believe in Birmingham for a study, as well as in several other centers.
I wish the best in getting things figured out!