Cystic Fibrosis

Cystic Fibrosis Test

The sweat chloride test is a common and simple test used to evaluate a patient who is suspected of having cystic fibrosis (CF), the most common lethal genetic disease affecting Caucasians.

Cystic fibrosis facts*

*Cystic fibrosis facts medical author: Melissa Conrad Stöppler, MD

  • Cystic fibrosis (CF) is an inherited disease that affects the secretory glands, including the mucus and sweat glands. Cystic fibrosis mostly affects the lungs, pancreas, liver, intestines, sinuses, and sex organs.
  • CF is due to a mutation in the CF gene on chromosome 7. The CF gene encodes a protein known as the cystic fibrosis transmembrane regulator (CFTR). The abnormal CFTR protein in patients with CF leads to disruption of chloride channels on the cells.
  • CF is characterized by the production of abnormal mucus that is excessively thick and sticky. The abnormal mucus leads to blockages within the lungs and airways. This leads to repeated, serious lung infections that can damage the lungs.
  • Lung function often starts to decline in early childhood in people who have cystic fibrosis. Over time, permanent damage to the lungs can cause severe breathing problems.
  • The thick, sticky mucus also can block tubes, or ducts, in the pancreas. As a result, the digestive enzymes from the pancreas can't reach the small intestine, causing impaired absorption of fats and proteins. This can cause vitamin deficiency and malnutrition.
  • Due to the defect in chloride channels, CF fibrosis also causes the sweat to become very salty.
  • Every person inherits two CFTR genes -- one from each parent. CF is inherited in an autosomal recessive manner; children who inherit a faulty gene from each parent will have cystic fibrosis.
  • Children who inherit one faulty gene and one normal gene will be "CF carriers." Cystic fibrosis carriers usually have no symptoms of cystic fibrosis, but they can pass the faulty gene on to their children.
  • About 30,000 people in the United States have cystic fibrosis. It is one of the most common inherited diseases among Caucasians. About 1,000 new cases of cystic fibrosis are diagnosed each year.
  • The symptoms of cystic fibrosis vary from person to person and over time.
  • Doctors diagnose cystic fibrosis based on the results from various tests. The most commonly used test is a sweat chloride test, which measures the concentration of chloride in sweat. Direct genetic testing to identify the CF mutation is also used. Most U.S. States screen newborns for cystic fibrosis.
  • Cystic fibrosis has no cure. However, treatments have greatly improved in recent years. Treatment may include nutritional and respiratory therapies, medicines, exercise, and more. Early treatment for cystic fibrosis can improve both quality of life and lifespan.
  • As treatments for cystic fibrosis continue to improve, so does life expectancy for those who have the disease. Today, some people who have cystic fibrosis are living into their forties, fifties, and older.

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