They can be very misleading when you are being told normal or borderline -- read my blog for more info.... many people here with confirmed genetics of CF have sweat test numbers in the teens and twenties ( a few are even down in the single digits) But here is the official scale:
under 40 == normal
40-60 == borderline
60+ == positive
Sweat test are really only accurate if you are over 60 -- anything below that with CF symptoms only causes confusion and misdiagnoses.
Full genetic testing, looking for all 1581 possible gene mutations is the only way to go.
<b>Oh wait ... now that I read your signature line I see your child already has confirmed CF gene mutations.... so perhaps I misunderstood your question....</b>
In the case of already knowing a person has CF and wondering what the sweat test number means.... it still means very little as far as what to expect from the severity of the disease..there is no correlation to that.... the sweat test numbers correspond to how much dysfunction there is in the cells/sweat chloride channels..... the higher the number the more dysfunction.... the only practical information you gain my knowing if your number is on the higher or lower side is how careful you have to be to watch out for dehydration on hot days or during exercise....someone with a high sweat test number (say over 75 or so) will be far more likely to need more salt, electrolytes and water after sweating during exercise or playing outside on a hot day.
Is that what you were asking?