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Test ID: CFTRZ CFTR Gene, Full Gene Analysis

Useful For

Follow-up testing to identify mutations in individuals with a clinical diagnosis of cystic fibrosis (CF) and a negative targeted mutation analysis for the common mutations

 

Identification of mutations in individuals with atypical presentations of CF (eg, congenital bilateral absence of the vas deferens or pancreatitis)

 

Identification of mutations in individuals where detection rates by targeted mutation analysis are low or unknown for their ethnic background

 

Identification of patients who may respond to cystic fibrosis transmembrane conductance regulator (CFTR) potentiator therapy

 

This is not the preferred genetic test for carrier screening or initial diagnosis. For these situations, order CFB / Cystic Fibrosis Mutation Analysis, 106-Mutation Panel

Testing Algorithm

See Cystic Fibrosis Molecular Diagnostic Testing Algorithm in Special Instructions for additional information.

Method Name

Polymerase Chain Reaction (PCR)/DNA Sequencing/Dosage Analysis (Multiplex Ligation-Dependent Probe Amplification [MLPA])

Reporting Name

CFTR Gene, Full Gene Analysis

Specimen Type

Varies


Shipping Instructions


Specimen preferred to arrive within 96 hours of draw.



Specimen Required


Specimen Type: Whole blood

Container/Tube: Lavender top (EDTA) or yellow top (ACD)        

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Additional Information: Patient education brochures in English (T548) and Spanish (T563) are available upon request.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Varies Ambient (preferred)
  Frozen 
  Refrigerated 

Clinical Information

Cystic fibrosis (CF), in the classic form, is a severe autosomal recessive disorder characterized by a varied degree of chronic obstructive lung disease and pancreatic enzyme insufficiency. Clinical diagnosis is generally made based on these features, combined with a positive sweat chloride test or positive nasal potential difference. CF can also have an atypical presentation and may manifest as congenital bilateral absence of the vas deferens (CBAVD), chronic idiopathic pancreatitis, bronchiectasis, or chronic rhinosinusitis. Several states have implemented newborn screening for CF, which identifies potentially affected individuals by measuring immunoreactive trypsinogen in a dried blood specimen collected on filter paper.

 

If a clinical diagnosis of CF has been made, molecular testing for common CF mutations is available. To date, over 1,500 mutations have been described within the CF gene, named cystic fibrosis transmembrane conductance regulator (CFTR). The most common mutation, deltaF508, accounts for approximately 67% of the mutations worldwide and approximately 70% to 75% in the North American Caucasian population. Most of the remaining mutations are rather rare, although some show a relatively higher prevalence in certain ethnic groups or in some atypical presentations of CF, such as isolated CBAVD.

 

The recommended approach for confirming a CF diagnosis or detecting carrier status begins with molecular tests for the common CF mutations (eg, CFB / Cystic Fibrosis Mutation Analysis, 106-Mutation Panel). This test, CFTR Gene, Full Gene Analysis may be ordered if 1 or both disease-causing mutations are not detected by the targeted mutation analysis (CFB / Cystic Fibrosis Mutation Analysis, 106-Mutation Panel). Full gene analysis, sequencing and dosage analysis of the CFTR gene, is utilized to detect private mutations. Together, full gene analysis of the CFTR gene and deletion/duplication analysis identify over 98% of the sequence variants in the coding region and splice junctions.

 

Of note, CFTR potentiator therapies may improve clinical outcomes for patients with a clinical diagnosis of CF and at least 1 copy of the G178R, G551S, G551D, S549N, S549R, G1244E, S1251N, S1255P, or G1349D mutation.

 

See Cystic Fibrosis Molecular Diagnostic Testing Algorithm in Special Instructions for additional information.

Reference Values

An interpretive report will be provided.

Interpretation

All detected alterations are evaluated according to American College of Medical Genetics recommendations.(1) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

Clinical Reference

1. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med 2015 May;17(5):405-424

2. Rosenstein BJ, Zeitlin PL: Cystic fibrosis. Lancet 1998 Jan 24;351(9098):277-282

3. Strom CM, Huang D, Chen C, et al: Extensive sequencing of the cystic fibrosis transmembrane regulator gene: assay validation and unexpected benefits of developing a comprehensive test. Genet Med 2003 Jan-Feb;5(1):9-14

4. De Boeck K, Munck A, Walker S, et al: Efficacy and safety of ivacaftor in patients with Cystic Fibrosis and the G551D gating mutation. J Cyst Fibros 2014 Dec;13(6):674-680 doi: 10.1016/j.jcf.2014.09.005

Day(s) and Time(s) Performed

Performed weekly; Varies

Analytic Time

14 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81223-CFTR (cystic fibrosis transmembrane conductance regulator) (eg, cystic fibrosis) gene analysis; full gene sequence

81222

LOINC Code Information

Result ID Test Result Name Result LOINC Value
53784 Result Summary 50397-9
53785 Result In Process
53786 Interpretation In Process
53787 Additional Information 48767-8
53788 Specimen In Process
53789 Source 31208-2
53790 Released By No LOINC Needed

Forms

1. Molecular Genetics: Congenital Inherited Diseases Patient Information (T521) in Special Instructions

2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-inherited-molecular