|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.
sequencing 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.
than 97% for nucleotides analyzed. All reports will indicate if
a certain percentage of nucleotides were not called or were analyzed
in a single direction.
MLPA: Greater than 99% for MLPA probes
|Turn Around Time:||
Sequencing: 3-4 weeks
approximately 3 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
83891 x 1; 83898 x 31; 83904 x 38; 83909 x 38; 83912 x 1
2013 CPT Code: 81223
MLPA: $429 for routine testing on a
2013 CPT Code: 81222
Please contact the lab to arrange testing for known mutations on blood or prenatal samples.
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.