Cystic Fibrosis (CF): CFTR (Full Gene Sequencing)

CPT: 81223
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Test Details

Test Includes

This test covers all coding nucleotides of gene CFTR, plus at least two and typically 20 flanking intronic nucleotides upstream and downstream of each coding exon, covering the conserved donor and acceptor splice sites, as well as typically 20 flanking nucleotides in the 5′ and 3′ UTR. In addition, the TG tract adjacent to the 5T/7T/9T polymorphism near the intron 9 acceptor site and the intronic region covering position c.3718-2477 are also analyzed (note that intron 9 is referred to as intron 8, if exon 6a/b nomenclature is used, and that c.3718-2477 is commonly known as 3849+10kb).

Use

Confirm a clinical diagnosis of CF; predict risk of CF in blood relatives

Limitations

This method does not reliably detect mosaic variants; large deletions; large duplications, inversions, or other rearrangements; or deep intronic variants. It may be affected by allele dropout, it may not allow determination of the exact numbers of T/A or microsatellite repeats, and it does not allow any conclusion as to whether two heterozygous variants are present on the same or on different chromosome copies.

Methodology

DNA sequencing

Reference Interval

Normal equals reference sequence or variants that are known or predicted to be benign; abnormal equals all other variants.

Additional Information

Cystic fibrosis (CF) is a relatively common, recessively inherited multisystem disease affecting the respiratory, digestive, and male reproductive systems. Disease severity can range from recurrent sinusitis and bronchitis with onset in young adulthood (nonclassic CF) or, in males, from infertility without any pulmonary manifestations (congenital absence of vas deferens) to severe lung, pancreatic, and liver disease with onset in infancy or childhood (classic CF). Genetic testing can confirm a diagnosis based on sweat testing, transepithelial nasal potential difference, or immunoreactive trypsinogen assay and identify the exact CFTR mutations underlying disease in the individual patient. Genetic testing for presence of these familial mutations can then identify disease carriers in the patient's blood relatives, allowing reproductive counseling. In males with CAVD or individuals with nonclassic CF, analysis of the 5T/TG tract, which is known to modify severity of certain "mild" CFTR mutations, can help to predict the risk of CF in blood relatives.

Specimen Requirements

Specimen

Whole blood; DNA is accepted (Call 800-345-4363 for DNA collection information.)

Volume

2 mL

Container

Lavender-top (EDTA) tube

Storage Instructions

Maintain specimen at room temperature.

Causes for Rejection

Container broken or leaking; container not labeled or label not legible; use of improper anticoagulant

Clinical Information

Special Instructions

In cases in which a known mutation can be documented, the physician may prefer to order Cystic Fibrosis (CF): CFTR (Known Mutation) [252760].

References

Moskowitz SM, Chmiel JF, Sternen DL, et al. Clinical practice and genetic counseling for cystic fibrosis and CFTR-related disorders. Genet Med. 2008; 10(12):851-868.19092437
Watson MS, Cutting GR, Desnick RJ, et al. Cystic fibrosis population carrier screening: 2004 revision of American College of Medical Genetics mutation panel. Genet Med. 2004; 6(5):387-391.15371902

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
252763 Cystic Fibrosis (CF): CFTR 21654-9 252075 Routing 21654-9

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