Lab Test

Cystic Fibrosis (CFTR Gene) Carrier Screening

Test Codes

Integrated Genetics: 530 EPIC: LAB8519, Beaker: XCFMA

Department

Molecular Pathology

Specimen Collection Criteria

Collect (preferred specimen): 

Two Lavender-top EDTA tube. (Minimum: 5.0 ml)

Physician Office/Draw Specimen Preparation

Do not freeze specimens. Maintain whole blood at room temperature (20-26°C or 68-78.8°F) prior to transport.

The information below is requested for testing:

  1. Patient ethnicity (European Caucasian, Ashkenazi Jewish, African American, Hispanic American, Asian American or other and mixed ethnicity).
  2. Family history (positive or negative for cystic fibrosis).
  3. Indication for performing the test (carrier screening or diagnostic).

A form to document this information can be printed from the following link:

Clinical Information Form

Preparation for Courier Transport

Transport: Whole blood at room temperature (20-26°C or 68-78.8°F).

Rejection Criteria

  • Frozen specimens.
  • Unlabeled tubes.
  • Specimens collected in heparin (Green-top), clot tubes (Red-top), or SST tubes.
  • Specimens that are not accompanied with the necessary patient information will be tested only after obtaining the required additional information.

This test will only be performed once in a lifetime for the purposes of carrier screening.

In-Lab Processing

Do not centrifuge or freeze specimens. Refrigerate (2-8°C or 36-46°F) specimens that will not be tested within 72 hours.

Storage

Specimen Stability for Testing:

Whole Blood
Room Temperature (20-26°C or 68-78.8°F): 72 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to LabCorp Integrated Genetics, Westborough, MA

Performed

Varies.
Results available in 6-13 days.

Reference Range

Positive or negative for CFTR gene mutation(s); An interpretive report will be issued

Test Methodology

  • DNA is isolated from the sample and regions of the CFTR gene are amplified enzymatically and subjected to a solution-phase multiplex allele-specific primer extension with subsequent hybridization to a bead array and fluorescence detection. Some mutations are then specifically identified by bidirectional dideoxysequencing. Discriminates between p.F508del and the following polymorphisms: F508C, I506V, and I507V p.F508C, p.I506V, and p.I507V. The panel includes the 23 mutations and variants currently recommended by the American College of Medical Genetics and Genomics (ACMGG) and the American College of Obstetricians and Gynecologists (ACOG) as well as 74 116 other mutations.

Interpretation

  • Cystic Fibrosis (CF) is a relatively common autosomal recessive disorder affecting approximately 1 in 3,300 people in the United States. It is characterized by sweat gland dysfunction, chronic obstructive pulmonary disease, and exocrine pancreatic dysfunction, and is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. This gene codes for a chloride transporter protein found in the membrane of epithelial cells of airways, sinuses, the gastrointestinal tract including the pancreas and biliary system, sweat glands, and the genitourinary tract.  Depending on which of the over 2000 characterized CFTR mutations is present, the disease can present as a multisystem disorder or can be confined to a single organ. Symptoms associated with CF arise from altered viscosity of mucus secretions which accumulate in various tissues such as the lung leading to pulmonary dysfunction and pneumonia or the pancreas leading to pancreatic dysfunction and malabsorption. The phenotype and severity ranges from mild to severe, with 70% of Caucasians with CF carrying two copies of the DF508 mutation leading to classic severe CF. While the median age of survival is currently 29.4 years, the life span of individuals with CF is expected to increase with the development of targeted therapies.
  • About 1 in 25 (~4%) Caucasians and 1% or greater in other population groups are carriers of a CFTR gene mutation.  The purpose of carrier screening as recommended by ACMGG and ACOG is to identify individuals with or without a family history of CF who may be at increased risk of having children affected with CF. This test detects 139 clinically relevant cystic fibrosis disease-causing mutations and variants within the CFTR gene.

Clinical Utility

  • Pre- and Post-test genetic counseling is strongly recommended and is the responsibility of the ordering physician
  • This is a carrier screening test.
  • The laboratory strongly recommends sequential screening of partners.
  • The panethnic CF panel is recommended by ACOG (American College of Obstetricians and Gynecologists) and ACMG (American College of Medical Genetics) for all couples seeking prenatal or preconception care  

CPT Codes

81220

Contacts

Last Updated

8/11/2021

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