GeneDx can provide Mutation-Specific Testing for known familial mutations, in any gene, for families that have had previous testing at GeneDx or elsewhere.  Mutation-Specific Testing always requires that sufficient information is provided (see links below for details).  Mutation-Specific Testing is offered for both symptomatic and asymptomatic individuals, and for dominant or recessive mutations.  Mutation-Specific Testing is less costly and more rapid than diagnostic analysis of the whole gene.  Pricing is dependent on whether testing is done for one or two mutations.

Choose one of the following links for specific step-by-step instructions

  Family Member Previously Tested at GeneDx 

  Family Member Previously Tested at an Outside Laboratory

Reasons for Performing Mutation-Specific Testing:

1. Targeted mutation testing in the parents of a child with a specific dominant mutation, in order to determine if the mutation was inherited or newly acquired (de novo).
2. Carrier testing for the parents of a child apparently homozygous for a recessive mutation, to rule out the possibility that the child has one mutated allele and one allele that is deleted or refractory to amplification.
3. Carrier testing for the parents of a child who has two mutations associated with a recessive disorder to confirm that the mutations are present on two different alleles and that all four parental alleles can be detected prior to prenatal diagnosis.
4. Pre-symptomatic testing in siblings of the index case.
5. Mutation-specific testing in the extended family.
6. Clinical laboratory confirmation of one or more mutations identified in a research lab.

Testing methods:

- Family member previously tested at GeneDx

Using genomic DNA, the regions of interest are examined by bi-directional sequence analysis and/or by other methods, such as heteroduplex analysis or restriction enzyme digestion. The previously tested proband’s DNA serves as the positive control.

- Family member previously tested at an Outside Laboratory

GeneDx performs the analysis using information provided by the referring clinician or laboratory and requests submission of a positive control specimen. Primers are designed and ordered by GeneDx based on the information provided.
If the individual being tested is NOT the proband who was previously tested by the outside laboratory, a sample from a related individual known to have the mutation(s) of interest must be provided. Analysis is performed by PCR amplification of the region of interest in the gene using either bi-directional DNA sequencing or another appropriate method.  

- Testing for a known familial gene deletion/duplication

PCR and sequencing based methods can identify the majority of mutations that are associated with genetic disease, but deletions spanning one or more exons, complete gene deletions, gene rearrangements, or duplications may not be detected. To evaluate for a known familial gene deletion or duplication, GeneDx offers quantitative gene copy number analysis, using either targeted array CGH analysis with exon-level resolution (ExonArrayDx), CopyDx (quantitative PCR) or Muliplex Ligation-Dependent Probe Amplification (MLPA). The testing process is similar to that explained above, including the need for a positive control specimen. However, please note that this analysis requires a blood sample in EDTA and CANNOT be performed on buccal swabs.