The blood work that is done on an infant to test for cystic fibrosis (CF) is a genetic test. This test looks for any genetic changes that would cause CF. The "gold standard" or best test to look for CF is not a blood test. It is called a sweat test. A chemical is placed on the skin, stimulated with an electrode to trigger sweating, the sweat is collected, and the amount of chloride in the sweat is measured. A high amount of chloride in the sweat means CF. Sometimes the newest test is used to find CF. It is called a nasal potential difference (NPD). Electrodes are placed inside the nose to measure electrical currents. High measurements mean CF.
they usually test the skin for sweat hence a sweat test....there may be a blood test but im not sure