Cystic fibrosis (CF)

Cystic fibrosis (CF) - a life-threatening disorder that causes severe lung damage and nutritional deficiencies - used to be a genetic mystery, and most people with the disease didn't live beyond their teens. But researchers have made progress in unraveling the genetic basis of CF, which has led to earlier detection. In addition, improved and more consistent treatments now allow people with CF to live into their 30s and 40s and even beyond, and to have fuller, more comfortable lives.

When to seek medical advice 

See your doctor if you suspect your child has CF. Signs and symptoms in newborns may include failure to grow, chronic respiratory problems — especially recurrent pneumonia — and frequent bulky, greasy stools. Older children also may have diarrhea and frequent respiratory infections, including pneumonia. Failure to grow steadily on the growth percentile curve may also be a sign of CF, especially if other signs and symptoms are present. Call your doctor right away if, after diagnosis, your child develops fever, a worsening cough, breathing difficulties, change in level of tiredness or decreased appetite.

In addition, if your child has received a diagnosis of CF, schedule regular examinations at a CF clinical center. Your child will also need to see your family doctor on a regular basis to have medications and any lung or digestive problems monitored.

• Diarrhea
• Pneumonia

Screening and diagnosis 

If you're pregnant or trying to become pregnant, you may want to consider talking to your doctor about a CF carrier test for you and your partner. In the past, doctors usually tested only couples at increased risk — those with a personal or family history of CF — but many doctors now offer the test to all couples.

The test, which is performed in a lab on a sample of blood or saliva, can help determine whether you or your partner carries the gene for CF. If you're already pregnant and the test shows that your baby may be at risk of CF, your doctor can conduct additional tests on your developing child. Because cystic fibrosis can't be treated before birth, the purpose of these tests is to help you consider your plans for the future.

The decision to be screened for CF is personal and will depend on a number of factors, including your level of risk and your religious beliefs. In addition, some genetic mutations for CF can't be detected by the current test. That means that in rare cases, your test may be normal and yet you may still be a carrier. The chances of this happening are small, however.

Sweat test
The standard diagnostic test for CF is a sweat test, which measures the amount of sodium or chloride in a person's sweat. During the procedure, a small amount of an odorless sweat-producing chemical is applied to a small area on the arms or legs. An electrode attached to the area stimulates a very weak and painless electric current, causing a tingling or warm feeling. After several minutes, sweat is collected from the stimulated area and sent to a laboratory for analysis.

The sweat test is performed on two separate occasions to ensure that a false-positive or false-negative result hasn't occurred. A consistently high level of salt indicates CF. This test doesn't show whether someone has a mild or severe case of the disease, however, and it can't predict how well someone with CF will do.

In addition, the sweat test may not always be useful in newborns. That's because babies may not produce enough sweat for a reliable diagnosis in the first month of life. For this reason, doctors usually don't perform a sweat test until an infant is at least several months old.

Other tests
If your newborn has signs and symptoms of CF, your doctor may perform a genetic analysis of a blood sample to confirm the diagnosis. Tests may also help determine the extent and severity of CF. Among these are tests to measure how well the lungs, pancreas and liver are working.

Because CF is an inherited disease, your doctor may suggest testing the brothers and sisters of a child with CF, even if they show no symptoms. Other family members, especially first cousins, also may want to be tested. In most cases family members can be screened with a sweat test, although in some cases genetic testing may be appropriate.