Last updated March 15, 2022

Molecular Testing For Cystic Fibrosis Carrier Status

RECOMMENDATIONS

COUNSELING ABOUT CF AND THE CFTR‐RELATED DISEASE SPECTRUM

While most positive CF carrier screening results identify mutations associated with classic CF disease, genetic counselors offering CF carrier screening should ensure that they are providing the most current information to patients regarding the range of symptoms, potential treatment options, and quality of life issues associated with CF and the CFTR‐related disease spectrum.
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TO WHOM SHOULD CARRIER TESTING FOR CF BE OFFERED?

Carrier testing for CF should be offered to all women of reproductive age, regardless of ancestry; preferably pre‐conceptionally. CF carrier testing should also be offered to any individual with a family history of CF and to partners of mutation carriers and people with CF.
 
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PRE‐TEST RISK ASSESSMENT

Pre‐test risk assessment should include an estimate of CF carrier frequency based on the individual's family history, ethnic background, and the predicted residual risk to have a child with CF if the test is negative.
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CF CARRIER TEST SELECTION

Carrier testing panels should include the mutations recommended by ACOG and ACMG. For individuals of non‐Northern European descent, pan‐ethnic panels that include additional mutations more commonly identified in minority populations are appropriate to consider. Focus general population CF screening practices on identifying carriers of established disease‐causing CFTR mutations.
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CHANGES IN TESTING PANELS AND INTERPRETATION

The inclusion and exclusion of mutations on available CFTR mutation screening panels remains a dynamic process as new information is learned about the pathogenicity of CFTR mutations. When individuals present for genetic counseling with prior carrier screening results, those results should be reviewed and re‐interpreted, if necessary, in light of current knowledge.
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COUNSELING COUPLES AT RISK TO HAVE A CHILD WITH CF

When both parents are known carriers for CF, available prenatal and pre‐implantation diagnostic testing should be offered. Prenatal facilitation of a monitoring plan should begin for couples at risk or who continue a pregnancy known to have CF, and postnatal evaluation through sweat testing and state NBS programs, should be discussed.
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THE R117H/POLY T and 5T/TG TRACT ALLELES

If a client is found to carry an R117H mutation, it is important to ensure the testing laboratory performs reflex testing for poly T status along with studies to determine the cis/trans orientation of the poly T alleles. In the absence of an R117H mutation, assessment of the intron 8 poly T or TG tracts is not recommended for routine CF carrier testing.
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INDIVIDUALS WITH ≥2 MUTATIONS IDENTIFIED BY CARRIER SCREENING

Identification of two or more mutations in a patient referred for routine carrier screening should lead to a referral for clinical diagnostic evaluation. If the mutations identified are uncommon CFTR sequence variants, the likelihood of pathogenicity may be refined through determination of phase (cis/trans orientation).
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CF GENOTYPE/PHENOTYPE CORRELATIONS

While some broad correlations can be made between genotype and anticipated phenotype, genetic counselors should not counsel regarding severity of disease course based on published case reports or individual patient experience.
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Recommendation Grading

Overview

Title

Molecular Testing For Cystic Fibrosis Carrier Status

Authoring Organization

Publication Month/Year

September 1, 2013

Document Type

Guideline

External Publication Status

Published

Country of Publication

US

Document Objectives

To provide practice recommendations for genetic counselors whose clients are considering cystic fibrosis (CF) carrier testing or seeking information regarding CF molecular test results. 

Target Patient Population

Patients who are considering cystic fibrosis carrier testing

Inclusion Criteria

Female, Male, Adolescent, Adult, Child, Older adult

Health Care Settings

Ambulatory, Outpatient

Intended Users

Nurse, nurse practitioner, physician, physician assistant

Scope

Counseling, Assessment and screening

Diseases/Conditions (MeSH)

D003550 - Cystic Fibrosis, D005820 - Genetic Testing, D000068617 - Genetic Background, D005823 - Genetics

Keywords

genetic testing, cystic fibrosis, genetic counselors