The day after DS was born, he ended up having surgery for a bowel obstruction. No family history of CF. Was a complete shock. He had two blood tests and a sweat test (at 3 weeks). One blood test was inconclusive because they didn't get a large enough sample. The sweat test was a 32 and then the blood test they did at the local hospital came back and it showed he had CF.
Push for more extensive testing. Find a proactive doctor. You don't want to be wasting time waiting when your child may not be getting proper treatment -- nutritional, lung, etc.