CFTR TARGETED MUTATION ANALYSIS FOR CYSTIC FIBROSIS
Label Name: CFTR MUTN AN
Lab Discipline: Molecular Diagnostics
Institution:  Duke University Health System 
EAP ID:  LAB6165 
Last Review:  3/17/2017 10:13:42 AM
Specimen Type
  Whole Blood (EDTA)
Container & Volume
  Age Group   Container   Volume  
  0  - 18 Years LAVENDER TOP TUBE 3  ML
Label Reminders
  Be sure to include the patient's name, history #, date and time of collection, and collector's initials.
Collection Notes
  All:
  • Peripheral Blood: One lavender-top EDTA tube (minimum of 1 mls) is required for testing. Forward unprocessed peripheral blood promptly to the laboratory at ambient temperatures. THE SPECIMEN CANNOT BE FROZEN. GREEN-TOP (HEPARIN) TUBES ARE NOT ACCEPTABLE FOR TESTING.


 
Storage
  DO NOT CENTRIFUGE. DO NOT FREEZE.
Transport
  Deliver peripheral blood to lab at ambient temperature. If there is a delay of more than 24 hours in delivery, refrigerate the sample. DO NOT FREEZE.
Turn Around Time -  Routine: 10 days   Stat: N/A
Reference Values
CFTR MUTN AN
Mutation not detected
Methodology
  The eSensor technology uses a solid-phase electrochemical method for determining the
genotyping status of a defined panel of CF mutations. Purified genomic DNA is isolated
from the patient specimen according to defined laboratory procedures and is amplified in a multiplex PCR reaction using specific primers and enzyme. The amplified DNA is converted to single stranded DNA via exonuclease digestion and is then combined with a signal buffer containing a pair of ferrocene-labeled, allele-specific oligonucleotide
signal probes for each polymorphism. The mixture of amplified sample and signal buffer is loaded onto the eSensor cartridge, which contains single stranded oligonucleotide capture probes bound to gold-plated electrodes. The cartridge is inserted into the XT- 8 instrument where the single stranded targets first hybridize to the matched signal
probes and then hybridize to the complementary sequences of the capture probes. The genotype of each polymorphism is determined by voltammetry, which generates specific electrical signals from the ferrocene-labeled, allele-specific signal probes.
   
Special Information
  All:
  • Additional Patient Information Required: Additional Patient Information Required: Due to the unique nature of genetic testing, patients offered this test should receive pre-test and post-test genetic counseling. Counseling should help the patient understand the strengths and limitations of DNA testing and the medical implications for the patient as well as for other family members. Patients are also required to give consent for testing.
 
   
Clinical Significance and Interpretive Data
    BACKGROUND AND CLINICAL SIGNIFICANCE:

Cystic Fibrosis (CF) is a disease caused by an inherited genetic defect, and is the most common lethal autosomal recessive disorder in the Caucasian population. There is an estimated incidence of 1 in 2500 newborns, with 1 in 25 Caucasians being heterozygous carriers. Cystic fibrosis results from mutations in the cystic fibrosis conductance regulator (CFTR) gene located on the long arm of chromosome 7. Mutations in the gene for CFTR result in abnormalities in chloride transport across epithelial cells on mucosal surfaces. The failure of epithelial cells to appropriately transport chloride ions and the associated water imbalance results in viscous secretions in the respiratory tract, pancreas, gastrointestinal tract, sweat glands, and other exocrine tissues. Some of the pathological consequences of CF include chronic bronchiolitis and bronchitis, chronic pancreatitis, and infertility. To date, more than 1000 different mutations in the CFTR gene have been identified. Half of affected individuals of northern European descent are homozygous for the delta F508 mutation. The remaining individuals harbor an array of other possible mutations. Different ethnic groups have differences in the distribution of mutations associated with cystic fibrosis. Thus the positive and negative predictive value of CF mutation testing differs for different ethnic backgrounds. Polymorphisms in the CFTR poly T tract, a string of thymidine bases located in intron 8 of the CFTR gene, can also be associated with CFTR-related disoders. The three common variants of the poly T tract are 5T, 7T, and 9T. Both 7T and 9T are considered normal variants. 5T is a variably-penetrant mutation. The 5T variant is thought to decrease the efficiency of intron 8 splicing. Poly-T testing is appropriate as a reflex test when a R117H mutation is detected or an adult male is being evaluated for Congenital bilateral absence of the vas deferens, a disease associated with the 5T variant.

REFERENCES:

Grody WW et al (2001) Laboratory Standards and Guidelines for Population Based Cystic Fibrosis Carrier Screening ACMG Guidelines. Genetics in Medicine. 3(2): 149-154

Grody WW (1999) Cystic Fibrosis, Molecular Diagnosis, Population Screening, and Public Policy. Archives of Pathology and Laboratory Medicine. 123: 1041-1046.

Rowe SM et al (2005) Cystic Fibrosis. NEJM 352(19): 1992-2001.

Watson SM et al. Cystic fibrosis population carrier screening: 2004 revision of American College of Medical Genetics mutation panel. Genetics in Medicine. 6(5): 387-391.


Moskowitz SM, et al. CFTR-Related Disorders. In: Pagon RA, Bird TD, Dolan CR, Stephens K, editors. GeneReviews [http://www.ncbi.nlm.nih.gov/books/NBK1250/]. Seattle (WA): University of Washington, Seattle; 1993-2001 Mar 26 [updated 2008 Feb 19].

http://www.accessdata.fda.gov/cdrh_docs/reviews/K090901.pdf
   
Indications
    Molecular testing for CFTR mutations can be used for the definitive diagnosis of cystic fibrosis and for carrier screening. Indications for testing include:

A clinical suspicion of cystic fibrosis.

Infants with meconium ileus
Infants with hyponatremia and hypochloremia of unknown etiology
Infants with hypoproteinemia and anemia
Children with rectal prolapse
Children with failure to thrive, poor growth and weight gain, nutritional problems, chronic diarrhea, or malabsorption
Children with refractory asthma, recurrent pneumonia or sinusitis, and/or nasal polyps.
Adolescents or adults with recurrent pancreatitis
Adults with recurrent sinusitis/bronchitis or bronchiectasis, nasal polyps, recurrent pancreatitis, and male infertility

The American College of Medical Genetics recommends carrier screening in any woman who is pregnant or considering becoming pregnant.


The test is not indicated for use in fetal diagnostic or pre-implantation testing. This test is also not indicated for stand-alone diagnostic purposes and results should be used in conjunction with other available laboratory and clinical information

   
Limitations
    This assay detects only the mutations listed above. The following information is based on testing of the ACMG 23 mutation panel and may be used in the genetic counseling of individuals undergoing carrier screening.

The mutation detection rate, the estimated risk of carrying a single mutation before testing and the estimated residual risk of carrying a single mutation after a negative test result for the listed ethnic populations are:

Ashkenazi Jewish: 94.0%, 1/23, ~1/384
European Caucasian: 88.3%, 1/25, ~1/206
African American: 64.5%, 1/61, ~1/171
Hispanic Caucasian: 71.7%, 1/58, ~1/203
*Asian-American: 48.9%, 1/93, ~1/183

*The proportion of detectable mutations and the prevalence of CF for Asian American group are poorly defined. There is insufficient data for the Asian-American population to allow accurate prediction of residual risk following a negative test result.

Note: Residual carrier risk after a negative result is modified by the presence of a positive family history of CF. This has not been accounted for in this data.

Reference:

http://www.accessdata.fda.gov/cdrh_docs/reviews/K090901.pdf

   
Test Synonyms
  Synonym(s): 
Synonym(s): CF
Synonym(s): CFTR
Synonym(s): Cystic Fibrosis
Molecular Diagnostics Laboratory
(MDX)

Medical Director:
 Michael Datto, M.D., Ph.D.
 Phone: 919-684-6965
 Email: michael.datto@duke.edu
Lab Director:
 Catherine Rehder Ph.D, FACMG
 Phone: 919-613-8434
 Email: catherine.rehder@duke.edu
Lab Director:
 Siby Sebastian Ph.D., DABMG
 Phone: 919-613-8432
 Email: siby.s@duke.edu

Address: 
 Wadsworth Bldg, Cytogenetics, Rm 0220
 2351 Erwin Rd
 Durham,  NC  27705
 Phone: 919-684-2698
 FAX: 919-668-5424

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