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Test ID: CFTRZ CFTR Gene, Full Gene Analysis, Varies

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 CFP / Cystic Fibrosis Mutation Analysis, 106-Mutation Panel, Varies

Testing Algorithm

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

Method Name

Custom Sequence Capture and Targeted Next-Generation Sequencing (NGS) followed by Polymerase Chain Reaction (PCR) and Sanger Sequencing (when appropriate) and Gene Dosage Analysis by Multiplex Ligation-Dependent Probe Amplification (MLPA)

Reporting Name

CFTR Gene, Full Gene Analysis

Specimen Type

Varies


Advisory Information


For first-tier cystic fibrosis molecular testing, order CFP / Cystic Fibrosis Mutation Analysis, 106-Mutation Panel, Varies



Shipping Instructions


Specimen preferred to arrive within 96 hours of collection.



Specimen Required


Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

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:

1. To ensure minimum volume and concentration of DNA is met, the preferred volume of blood must be submitted. Testing may be canceled if DNA requirements are inadequate.

2. 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 Special Container
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, CFP / Cystic Fibrosis Mutation Analysis, 106-Mutation Panel, Varies). This test, CFTR Gene, Full Gene Analysis, Varies may be ordered if 1 or both disease-causing mutations are not detected by the targeted mutation analysis. Full gene analysis, through 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, FDA guidance has indicated that CFTR potentiator or combination chemical chaperone/potentiator therapies may improve clinical outcomes for patients with a clinical diagnosis of CF and at least 1 copy of a small subset of mutations. If one of the mutations associated with an FDA-approved therapy is identified, this information will be included in the interpretive report.

 

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 and Genomics (ACMG) 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

5. Currier RJ, Sciortino S, Liu R, et al: Genomic sequencing in cystic fibrosis newborn screening: what works best, two-tier predefined CFTR mutation panels or second-tier CFTR panel followed by third-tier sequencing? Genet Med 2017 Oct;19(10):1159-1163

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

81222

81479 (if appropriate for government payers)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CFTRZ CFTR Gene, Full Gene Analysis 90256-9

 

Result ID Test Result Name Result LOINC Value
53784 Result Summary 50397-9
53785 Result 82939-0
53786 Interpretation 69047-9
53787 Additional Information 48767-8
53788 Specimen 31208-2
53789 Source 31208-2
53790 Released By 18771-6

Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

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

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-inherited-molecular