Yup, I've had the test 1/year for the past 10 years.
And it missed my diabetes. I got a false negative from the oGTT.
It wasn't until I did a 2 week diary of my sugars that we saw how things really were.
My endo aptly described the difference like this - the OGTT is simply a snapshot of your pancreas is working at that very point in time. The 2 week diary shows the true changes in a CF pancreas.
LIke you said, you saw 130s one day with your DD, and then 160s another day. The OGTT won't capture these variations. The pancreas can decide to release a little bit more insulin on one day, but not another. Doesn't mean you don't have CFRD - those higher #s still do damage regardless of what the OGTT says.
Sounds like you're doing a great job tracking those sugars. I hope you will continue <img src="i/expressions/face-icon-small-smile.gif" border="0">