My 2yo might have CF. A few questions
Unfortunately, yes it is possible that weight gain problems might be all you will see for symptoms. <b>But it's also very possible it is not CF </b>and the doctors are doing a good job of ruling it out.
Something that <i>usually</i> goes along with CF & weight gain issues is very smelly bowel movements -- greesy, oily, orangish colored poo. Is that happening?
Sweat tests results can be available on the same day, but most places it is at least the very next day.
If you get a very clear low number, like under 10, you are probably in good shape, but if it comes back in the 20's or 30's you really need to look into genetic testing -- too many people on this board (my kids included) have normal or borderline sweat test numbers to believe that it is a full proof negative test. See my blog page for details about sweat testing and our personal experience with genetic testing.
Two things you want to make sure you know about the sweat test:
1) is it being administered by an accredited CF center? If not, get to an accredited center.
2) get the actual number - don't just settle for "negative" -- my daughter went undiagnosed for 8 years because she has a "normal" number -- you need to know what the number is (like I said above)
another next step would be to ask about fecal fat testing - this will tell them if there are enough enzymes getting into her system from the pancreas or not. Without enzymes she would not be able to digest her food correctly and therefore not be able to gain weight (and most likely have the very foul smelling and greasy poo). Many people with pancreatic insufficient CF take enzymes with their food, and they start gaining weight.
