Diagnostic Testing for CF

If Cystic Fibrosis is suspected for any reason, patients are referred to Stanford for testing. A complete diagnostic workup can be done at the clinic. Diagnostic tools include a sweat chloride test and a Cystic Fibrosis DNA mutation test.

In an effort to provide more than the commercial testing for the 70 most common mutations, our Center has published a method on complete genotyping. We also provide testing for Nasal Potential Difference on a research basis. Ours is one of only a few Centers in the country to offer this relatively new way helping to diagnose Cystic Fibrosis.

Sweat chloride, a non-invasive test, can aid in the diagnosis of Cystic Fibrosis because CF causes increased levels of sodium and chloride in the sweat. The test measures the level of chloride found in the sweat. No special preparation is necessary. The test is painless. An abnormal result may indicate the presence of Cystic Fibrosis.

CF DNA mutation analysis is a genetic test using either blood or a swab from the inner cheek. The test is used to diagnosis CF and also in research that is being done to search for a cure. NIH Consensus Statement

Everyone inherits two copies of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. However, some of the inherited copies are mutations (genetic material that is permanently changed in some way). Inheriting two mutated copies of this gene means that the person has Cystic Fibrosis. Inheriting only one copy of a mutated gene means that the person is a carrier for Cystic Fibrosis and could pass on a risk for CF to his or her childen.

Nasal Potential Difference  Persons with CF have an abnormal transport of salt (electrolytes) across the cell wall. This results in a potential difference or voltage across the cell which is different from people who do not have CF. Measurement of this potential difference in a person's nasal passages may be useful in confirming the diagnosis of CF.