If you or your partner has close relatives with cystic fibrosis, you both may choose to have genetic testing before having children. The test, which is performed in a lab on a sample of blood, can help determine your risk of having a child with CF. If you're already pregnant and the genetic test shows that your baby may be at risk of cystic fibrosis, your doctor can conduct additional tests on your developing child. Genetic testing isn't for everyone.
To diagnose cystic fibrosis, doctors typically do a physical exam, review your symptoms and conduct several tests. A blood sample is checked for higher than normal levels of a chemical called immunoreactive trypsinogen (IRT), which is released by the pancreas. A newborn's IRT levels may be high because of premature birth or a stressful delivery.
To evaluate if an infant has cystic fibrosis, doctors may also conduct a sweat test once the infant is at least 2 weeks old. A sweat-producing chemical is applied to a small area of skin. Then the sweat is collected to test it and see if it's saltier than normal.
Courtesy: Mayo Clinic