Cystic Fibrosis

(CF) Intron 8 5T/7T/9T

CF-5T

Test Synonym:

CF Intron 8 reflex testing

CPT Code:

83891-8A – Molecular isolation
83894-8A – Gel electrophoresis
83901-8A – Amplification each multiplex reaction
83896-8A X3 – Nucleic acid probes
83912-8A – Interpretation and report

Turnaround Time:

7-10 days

Methodology:

Polymerase Chain Reaction (PCR) / Oligonucleotide Ligation Asay

Specimen Requirements:

5.0ml (min. 3.0ml) whole blood EDTA preferred, ACD accepted

2 swabs of buccal cells in transport medium (provided)

2.0ml (min. 1.0ml) ThinPrep® PAP solution or SurePath™ Test Pack

Causes for Rejection:

Insufficient DNA material;, frozen; clotted or severely hemolyzed whole blood specimen

Specimen Stability

Blood stable at 18-25°C for 24 hours or 2-8°C for 4 days;

Buccal swab in transport medium and ThinPrep PAP solution or SurePath Test Pack stable at 18-25°C for 21 days

Storage and Handling:

Ship blood specimen at ambient temperature; If shipment is delayed, store blood at 2–8°C and ship with an ice pack (do not allow the sample to be in direct contact with the ice pack)

Ship buccal swabs in transport medium at ambient

Ship ThinPrep solution or SurePath Test Pack at ambient

Reference Range:

See report

Indication:

Cystic fibrosis (CF) is an autosomal recessive disease characterized by pulmonary and gastrointestinal manifestations of varying severity. Inherited mutations in the cystic fibrosis transmembrane regulator (CFTR) gene causes interference with chloride ion transport, resulting in decreased secretion and increased viscosity of fluids. These thick secretions lead to duct obstruction and organ dysfunction or failure. The intron 5T/7T/9T polymorphism affects the synthesis of a functional CFTR product, with the presence of a 5T allele resulting in a greater than 95% reduction in protein expression. The presence of the 5T allele, in combination with at least one known CF mutation (R117H) can modify the CF phenotype depending upon whether the 5T variant is on the same (“cis”) or opposite (“trans”) chromosome as the R117H mutation. R117H/5T in cis is associated with CF whereas R117H/5T in trans is associated with congenital bilateral absence of the vas deferens (CBAVD) in males.

At Molecular Pathology Laboratory Network we reflex to the CF Intron 8 5T/7T/9T test if a R117H mutation is found with the CF mutation panel in accordance with guidelines from the American College of Obstetricians and the American College of Medical Genetics. At Molecular Pathology Laboratory Network we also offer the CF mutation panel with the CF Intron 8 5T/7T/9T for individuals with CBAVD.

References:

ACOG and ACMG (2001). Preconception and Prenatal Carrier Screening for Cystic Fibrosis: Clinical and Laboratory Guidelines. Washington, DC: ACOG
Grody et al. (2001). Laboratory standards and guidelines for population-based cystic fibrosis carrier screening. Genet Med 3(2):14
Richards et al. (2002). Standards and Guidelines for CFTR Mutation Testing. Genet Med 4(5):379

*PCR is performed under license agreement with Hoffman-LaRoche, Inc