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Cystic Fibrosis Test

Genes:
CFTR

Syndrome Information

Clinical Description

Classic Cystic Fibrosis (CF) consists of progressive lung disease, exocrine pancreatic insufficiency, and male infertility.  Patients have elevated sweat chloride concentrations.  Patients sometimes termed 'non-classic' still meet diagnostic criteria for CF, but may have lower sweat chloride levels or may be pancreatic sufficient. 

CFTR-Related Disorder refers to patients older than 6 months with intermediate sweat chloride levels who may also have pancreatitis, chronic sinusitis, or infertility.  These patients are at risk for developing CF.

CFTR-Related Metabolic Syndrome is a diagnosis applied to an asymptomatic infant with an inconclusive diagnostic work-up after newborn screening. Follow-up is necessary until the clinician can include or exclude a diagnosis of CF.

Inheritance Pattern

Autosomal Recessive

Genotype-Phenotype Correlation

There is a correlation between pancreatic status and CFTR mutation; however, lung disease seems to be more highly influenced by environmental factors or other modifier genes.

Test Information

Test Method

Next Generation Sequencing (NGS) of the coding regions and intron-exon boundaries of CFTR; Deletion/Duplication:  Dosage analysis by normalization of NGS read depth for CFTR;  Sanger sequencing for potential fill in / confirmation 

This test is also available as part of one or more NGS panels for cystic fibrosis and related disorders.

Clinical Utility

Identification of causative mutations in known or suspected cases of cystic fibrosis; facilitation of targeted carrier testing of relatives; predictive prenatal testing when familial mutations are known.   

Clinical Sensitivity

This analysis will detect approximately 98% of CF mutations.  This analysis will not detect deep intronic mutations that may affect splicing other than those specifically listed.  It is estimated that about 2% of CFTR mutations in cystic fibrosis patients are large rearrangements, including deletions and duplications. This test is expected to detect two CFTR mutations in up to 99% of cystic fibrosis patients, but sensitivity may vary based upon ethnicity and clinical severity. 

Analytic Sensitivity

>99% for inherited single nucleotide and small insertion/deletion variants for the nucleotides evaluated; >99% for multi-exon deletions and >99% for single exon deletions; >99% for multi-exon duplications and >88% for single exon duplications.  Lower limit of detection for single nucleotide variants: 25% allele frequency (>99% sensitivity).

Sample Requirements

3-6ml whole blood in EDTA (purple topped) tubes. (see Pediatric or Adult blood sample algorithms for additional information)

We prefer whole blood for all tests.

Turn Around Time

Approximately 4 weeks

Fee and CPT Codes

$2450 for routine testing on a blood sample
CPT Code: 81223, 81222

Special Considerations

CFTR sequencing is most appropriate in the diagnostic setting when the patient has an atypical or non-classic presentation or when other mutation panels have failed to identify both causative mutations.  CFTR sequencing is not recommended in the carrier screening setting.

INFORMED CONSENT from the patient is required prior to ordering a genetic test. The DNA Diagnostic Lab's consent is located on the second page of the requisition form. There is also a patient brochure, "Things Every Patient Should Know Before Consenting to a Genetic Test", available for download.