First, I think you know the answer, but a test of 78 could be used to diagnose CF. The advent of genetic testing has taken over as the conclusive answer, but for years sweat tests were the rule. I would probably being looking at this from the standpoint of a positive diagnosis.
As for retest, most likely it is a pre-cursor to getting a genetic test. A borderline result is just that, a positive result it not likely going to come down. But a CF center will likely repeat the test and then send a blood sample for genetic confirmation.
It is not uncommon to have little or no symptoms, especially at your daughter's age. The benefit of knowing now is that most of the advancements in CF are proactive in that you can prevent or greatly delay problems. Once they develop the options drop; so knowing sooner can greatly improve outcome over time.
As for retest, most likely it is a pre-cursor to getting a genetic test. A borderline result is just that, a positive result it not likely going to come down. But a CF center will likely repeat the test and then send a blood sample for genetic confirmation.
It is not uncommon to have little or no symptoms, especially at your daughter's age. The benefit of knowing now is that most of the advancements in CF are proactive in that you can prevent or greatly delay problems. Once they develop the options drop; so knowing sooner can greatly improve outcome over time.