How is Cystic Fibrosis Diagnosed
Diagnosis of Cystic Fibrosis
The diagnosis of Cystic Fibrosis (CF) is most frequently made after positive newborn screening for CF. However, some people with CF are diagnosed as adults. For those who are not diagnosed as infants, the diagnosis is usually made after the primary care practionerhas concerns regarding signs and symptoms that may be suggestive of cystic fibrosis. These symptoms may include:
- Very salty-tasting skin
- Persistent coughing, at times with phlegm
- Frequent lung infections, such as pneumonia or bronchitis
- Wheezing or shortness of breath
- Poor growth or poor weight gain in spite of a good appetite
- Frequent greasy, bulky stools or difficulty in bowel movements
- Small, fleshy growths in the nose, called nasal polyps
- Chronic sinus infections
- Clubbing or enlargement of the fingertips and toes
- Rectal prolapse (when the rectum sticks out through the anus)
- Male infertility
The practitioner then refers the child to a Cystic Fibrosis Foundation (CFF) accredited lab for a sweat chloride test or to a CFF accredited care Center where evaluation and testing can be completed. A diagnosis of CF is possible when there are positive signs and symptoms of the disease, or a positive family history and a test that confirms the diagnosis of cystic fibrosis.
Sweat Test
The usual test for CF is a sweat test. This test is done at a special lab and involves a skin test which measures the amount of chloride (one of the body’s natural salts) in a collection of sweat. The test starts with the application of a chemical called pilocarpine to the skin, followed by a small electrical current that stimulates the sweat glands. The sweat is then collected and measured. Persons with cystic fibrosis have elevated or high levels of chloride in the sweat. This test takes about an hour to complete and the results are usually available the same day.
Genetic Testing
Another way to diagnose CF is to send a blood sample to check for the exact genes involved in CF. This test is more expensive and may miss some patients because of the many different gene mutations that can cause CF.as well as the inability to test for all of these different mutations in a single conventional test. Genetic testing is usually ordered when the sweat chloride test is unable to give an accurate result, or after diagnosis of CF occurs so that certain genotype-specific therapies for CF can be considered