How Cystic Fibrosis (CF) is Diagnosed

CF is a genetic disease affecting approximately 30,000 children and adults in the United States. Cystic Fibrosis may be diagnosed through tests such as: clinical signs, "sweat test", amniocentesis (with genetic analysis), or chorionic villi sampling (CVS) (with genetic analysis).

Diagnosis: based on sweat test with above 60 mEq/L Cl- and either pancreas involvement or recurrent lung infections; genetic testing for mutations; screening of newborns possible with blood trypsin value (Chymotrypsin?). Some clinics (e.g., Yale) are said to routinely perform two sweat tests before confirming diagnosis.

Genetic CF Test

In the past, blood tests were required to screen for gene mutations because DNA is present in most cells. White blood cells lining the mouth carry DNA. Called Buccal Cell DNA collection, a cheekbrush (a very small wand) is used to brush off a few cells from inside of the cheek. (There is another test which consists of rinsing the cells from the mouth with a special mouthwash). The fragments of DNA supplied by the cheek brushing are then synthesized to match known sequences in the CFTR gene in a process known as PCR - Polymerase chain reaction. PCR permits enough copied DNA to be harvested. Confirmation of a normal sequence can be performed by a number of standard genetic analysis techniques.