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Cystic Fibrosis Complete Rare Mutation Analysis, Entire Gene Sequence

Cystic Fibrosis Complete Rare Mutation Analysis, Entire Gene Sequence

Test Highlight

Cystic Fibrosis Complete Rare Mutation Analysis,
Entire Gene Sequence

Clinical Use

Cystic Fibrosis
 Test Selection Guide

  • Identify rare familial mutations in obligate cystic fibrosis (CF) carriers when they have tested negative in the routine screening test

  • Identify a rare mutation in a CF-affected person when that person has tested negative in the routine screen

Clinical Background

CF is an autosomal recessive disease that affects approximately 1 in 3,000 Caucasians. It also occurs in other ethnic groups, but at a lower rate. To date, more than 1,900 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene have been identified. The Quest Diagnostics routine carrier screening test detects 32 of these mutations (23 ACMG/ACOG recommended and 9 others), identifying a maximum of 94% of carriers (Ashkenazi Jewish population). In other populations, the detection rate can be substantially lower (eg, only 72% in the Hispanic American population). Use of the CF Complete® test, however, can dramatically increase the CF detection rate because it detects 99% of CFTR mutations. Nevertheless, the CF Complete test should not replace the general carrier screen test. Rather, the CF Complete test should be used to identify rare familial mutations in obligate CF carriers when they have tested negative in the routine screening test. CF Complete should also be used to identify a rare mutation in a CF-affected person when that person has tested negative in the routine screen.

Method

Genomic DNA is first isolated from the patient’s specimen. Using this genomic DNA and polymerase chain reaction (PCR), the entire coding region, as well as the splice junction sites and promoter region of the CFTR gene, is amplified. The resulting amplicons are then subjected to dye terminator cycle sequencing reactions. The sequencing reaction products are analyzed on an automated capillary DNA sequencer.

Interpretive Information

CF mutation detection by sequencing will detect 99% of known, as well as novel, CFTR mutations in all different ethnic groups. However, this test will not detect large deletion or duplication mutations, which should be detected with the Cystic Fibrosis Gene Deletion or Duplication assay [test code 16080(X)]. An individual positive for 1 copy of a known CF mutation is at least a CF carrier. Detection of 2 mutant alleles in conjunction with positive clinical findings or family history is consistent with CF. Individuals who test negative will still have a small risk of having unidentified CF mutations.

Additional assistance in interpretation of results is available from our Genetic Counselors by calling 866-GENE-INFO (866-436-3463).

 

This test was developed and its performance characteristics have been determined by Quest Diagnostics Nichols Institute. Performance characteristics refer to the analytical performance of the test.

Content reviewed 06/2013

 
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