Diagnosis Techniques Aplenty

In the United States, every newborn is screened for cystic fibrosis. This is a practice that is upheld in all 50 states. Typically, newborn screening is accomplished through either a genetic test or a blood test. The genetic test will show whether or not the baby has the CTFR gene while the blood test will show if the pancreas is working correctly.
If a genetic test indicates CF, the results can be confirmed using a sweat test. This test measures the amount of salt in sweat. Doctors will trigger sweat on a small patch of skin - usually on the arm or leg. They will then use an electrode to produce an electrical current, then take the sweat strip in for analysis. High levels produced two or more times confirm positive CF results.
Following this, the doctor may recommend further tests including genetic testing to determine what type of CTFR is causing CF; chest X ray to view any inflammation or scarring of the heart, lungs, and blood vessels; sinus X ray to detect sinusitis; lung function tests to determine how much air can be breathed in and out; and a sputum culture to detect the presence of any bacteria that may be causing an infection (since CF patients are at a higher risk for infection due to thicker mucus).
 Progression of the disease can be summed up as follows:

References:

http://www.nhlbi.nih.gov/health/health-topics/topics/cf/diagnosis