FDA approves DNA-based blood test to help detect cystic fibrosis.

The US Food and Drug Administration (FDA) has approved the first DNA-based blood test to help detect cystic fibrosis. The Tag-It Cystic Fibrosis Kit works by directly analyzing human DNA to find genetic variations indicative of the disease. The FDA says the test will used to help diagnose cystic fibrosis in children and to identify adults who are "carriers" of the gene variations.

The Tag-It test identifies a group of variations in a gene called the "cystic fibrosis transmembrane conductance regulator" (or CTFR gene)that causes cystic fibrosis. The FDA said in a press release that it approved Tag-It based on a manufacturer study of hundreds of DNA samples showing that the test identifies the CFTR gene variations with a high degree of certainty.

Since Tag-It detects a limited number of the more than 1,300 genetic variations identified in the DFTR gene, the test should not be used alone to diagnosis cystic fibrosis. Physicians should interpret test results in the context of the patient's clinical condition, ethnicity, and family history, the FDA cautions.