• Clinical Signs
• Sweat Test
• Amniocentesis (with genetic analysis)
• 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 (Chromotrypsin?). Some clinics (eg. Yale) are said to routinely perform two sweat tests before confirming diagnosis.

Genetic 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 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 cheekbrush are then synthesized to match known sequences in the CFTR gene in a process known as PCR - Polymerase chain reaction. PCR permits enough copird DNA to be harvested. Confirmation of a normal sequence can be performed by a number of genetic analysis techniques.

Is there another genetic test that could tell me if I am a carrier?

There is a test to determine if you are a carrier for several of the most common mutations that cause CF. There are more than 500 mutations identified so far, though, so the test can tell you if you are a carrier, but if it comes back negative you just only know it is unlikely.

Manifestations: sweat gland (high electrolytes); pancreatic disease (exocrine insufficiency, disruption of exocrine function); intestinal glands ( meconium ileus); diabetes due to destroyed pancreas; liver disease (biliary cirrhosis, biliary tract obstruction); dehydrated mucus in the airways; lung infections (chronic bronchopulmonary infection); reduced lung function, infertility in male (vas deferens blocked), less in female; all these result in reduced life expectancy.

Great phenotypic variations: Research is exploring the relationship between phenotype and genotype. However, this is extremely difficult to do for a variety of reasons including the large number of cystic fibrosis gene mutations, and lack of understanding of how CFTR function. To date correlation can be made about genotype and pancreatic (in)sufficiency (i.e. 15% of CFers are pancreatic resulting from multiple different mutations.

The Gibson-Cooke method of sweat testing is considered by most clinics to be the most accurate for cystic fibrosis.

The sweat test uses a chemical called pilocarpine to produce sweat and then the sweat is collected and its sodium chloride rate is measured. The general rule of thumb is that levels of sodium chloride greater than 60mEq/L are considered positive for cystic fibrosis.