FDA Approves DNA Test for Cystic Fibrosis

Test to Help Diagnose Children, Identify Adults With Related Genes

From the WebMD Archives

May 11, 2005 -- The FDA has approved the first DNA-based blood test to help detect cystic fibrosis.

The "Tag-It Cystic Fibrosis Kit" directly analyzes human DNA to find genetic variations indicative of the disease. The test will be used to help diagnose cystic fibrosis in children and to identify adults who are "carriers" of the gene variations, says the FDA.

"This test represents a significant advance in the application of genetic technology and paves the way for similar genetic diagnostic tests to be developed in the future," says Daniel Schultz, MD, director of the FDA's Center for Devices and Radiological Health, in a news release.

DNA Test Can't Stand Alone

The test -- made by Tm Bioscience Corporation of Toronto -- should not be the only method used to diagnose cystic fibrosis, says the FDA.

"Since Tag-It detects a limited number of the more than 1,300 genetic variations identified in the CFTR [cystic fibrosis] gene, the test should not be used alone to diagnose cystic fibrosis," says the FDA.

"Physicians should interpret test results in the context of the patient's clinical condition, ethnicity, and family history. Also, patients may need genetic counseling to help them understand their test results."

About Cystic Fibrosis

Cystic fibrosis is a serious genetic disorder affecting the lungs and other organs. Though treatment has greatly improved over the years, cystic fibrosis still often leads to an early death. Half of the people with cystic fibrosis die by the age of 30, says the FDA.

Cystic fibrosis is the No. 1 cause of chronic lung disease in children and young adults. It causes thick mucus to build up in the body's organs, primarily the lungs, leading to serious breathing problems, and pancreas, causing malnutrition.

As the most common fatal hereditary disorder affecting whites in the U.S., cystic fibrosis affects about one in 2,500 to 3,300 white babies, says the FDA.

About the DNA Test

The "Tag-It" test identifies a group of variations in a gene called the "cystic fibrosis transmembrane conductance regulator" (CFTR gene), which causes cystic fibrosis.

The FDA's approval was based on a study by the test's maker of hundreds of DNA samples. The study showed that the test identifies CFTR gene variations with a high degree of certainty, says the FDA. The manufacturer also provided a broad range of supporting literature, says the FDA.