|DNA Diagnostic Laboratory at Johns Hopkins|
Cystic Fibrosis: CFTR Gene Sequencing and deletion/duplication testing
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 asymptomatic infants with an inconclusive
diagnostic work-us after newborn screening. Follow-up is necessary until
the clinician can include or exclude the diagnosis.
|Inheritance Pattern:||Autosomal Recessive|
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.
and/or NextGen sequencing (NGS) of the coding regions and intron-exon boundaries of CFTR;
Automatically reflexed to MLPA for deletion/duplication detection if
sequencing is negative.
of causative mutations in known or suspected cases of cystic fibrosis; targeted carrier testing of relatives of
prenatal testing when familial mutations are known.
|Clinical Sensitivity:||Sequencing: Approximately 98% of
classic CF is caused by point mutations in the
CFTR gene. This sequence analysis will detect
>99% of those point mutations. This analysis
will not detect other types of mutations in the
It is estimated that about
2% of CFTR mutations are large rearrangements, including deletions
and duplications. This test will detect full gene deletions and most
previously reported multi- and single exon deletions and duplications, but
not translocations or rearrangements limited to an intron.
Sanger Sequencing: >97% for nucleotides analyzed. All reports will indicate if
a certain percentage of nucleotides were not called or were analyzed
in a single direction.
accuracy for inherited single nucleotide and small insertion/deletion
variants for the nucleotides evaluated. All reports will indicate if
a certain percentage of nucleotides were not called.
MLPA: Greater than 99% for MLPA probes
|Turn Around Time:||
Sequencing: 3 weeks
up to 4 weeks
For tests utilizing MLPA, we are only able
to accept whole blood drawn in EDTA (purple or lavender top) tubes and
Qiagen Puregene extracted DNA.
|Fee and CPT Codes:||
Sequencing: $2298 for routine testing on a blood sample
CPT Code: 81223
MLPA: $429 for routine testing on a
Please contact the lab to arrange testing for known mutations on blood or prenatal samples; Pricing and CPT codes will vary.
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.
CFTR deletion/duplication testing by MLPA
analysis can be ordered separately.
|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.|
Requisition and Billing forms
Link to clinical information on Cystic Fibrosis
Link to the Johns Hopkins CF Center
Link to the General Test Information page for a discussion of the uses and limitations of genetic testing
Patient and Family Page for general resources on genetic testing.