I'm not sure how it works in canada, but I'd say insist on getting the test done at the actual children's hospital, because that's the test which has been thoroughly developed and examined and has been developed through peer-reviewed processes.
On the "normal" sweat test, regardless of which of two collection methods are used, the scale is the one you referred to: <40 negative, 40-60 borderline and >60 positive, and the highest you can come up with physiologically is around 160 or 170.
I think it would be very reasonable for you to insist that your child be tested through a means which is well established. In fact, I think it would be reasonable to insist on doing both a genetic screen and a traditional sweat test.
Good luck!
In canada you have to have a referral to see any type of specialist right?