Cystic Fibrosis Carrier Testing

What causes CF?

Cystic fibrosis is an inherited genetic condition.  It is inherited in a recessive manner.  That means that both parents must be carriers to have an affected child.  Being a carrier does not affect a person’s health.  Only when both parents are carriers of CF can the disease occur in their children.  When both parents are carriers of CF, there is a 25% chance with each pregnancy that the child will have cystic fibrosis.

How does the carrier test work? 

Carrier testing is a special gene test.  Everyone has genes.  Genes are the blueprints that tell the body how to function.  Genes are found in cells, such as blood cells or skin cells.  If a gene has a problem (called a mutation) it does not work properly.  CF carrier testing is a blood test that looks for mutations in the CF gene.

How accurate is the test?

There are many possible mutations in the CF gene.  Some are rare, and there may be some that have not been discovered yet.  LabCorp tests for the most common CF mutations.  A negative test significantly lowers the chance that a person is a carrier, but there is still a small chance that a rare mutation is present.

The following table shows the chance of being a carrier of CF when the LabCorp test is negative.  This table applies only to those people who do not have a family history of CF.  For an individual with a family history and a negative CF test result, LabCorp will determine the specific risk of being a carrier of cystic fibrosis.

Ethnicity

Carrier detection rate for the 32 CF mutations

CF Carrier risk prior to testing

CF carrier risk after a negative result for 32 mutations

Ashkenazi Jewish

97%

1/25

1/800

Caucasian
(non-Hispanic)

90%

1/25

1/240

Hispanic American

67-73%

1/46

1/146 – 1/167

African American

69%

1/65

1/207

Other

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