Causes and Diagnoses

Causes and Diagnoses of Cystic Fibrosis

The cause of cystic fibrosis is an inherited defect in the CFTR gene, which produces a protein that controls the movement of water and salt in and out of cells. When the protein doesn’t work properly, the body creates thick, sticky mucus and sweat with a high concentration of salt. 

Each person inherits a CFTR gene from each parent. When both parents are carriers of a faulty CFTR gene, there is a 25 percent chance their child will develop cystic fibrosis.

Diagnosing cystic fibrosis

CF is generally diagnosed during a complete physical exam and with diagnostic tests, including:

  • Sweat test: High amounts of chloride in sweat may indicate cystic fibrosis.
  • Genetic test: Geneticists can identify mutations in the CFTR gene.
  • Blood test: Blood samples can be tested in the case of recurrent infections.
  • Sputum test: You may be asked to provide a sample of mucus to be checked for bacteria.
  • Pulmonary function test: This helps determine a patient's efficiency at exchanging oxygen and carbon dioxide.
  • Stool test: Stool fat absorption is an indicator of CF.

Diagnostic Tests