22q11.2 deletion syndrome

Diagnosis and Testing

How do I get tested for 22q11.2 deletion syndrome?

There are a few genetic tests that can diagnose 22q11.2 deletion including fluorescence in situ hybridization (FISH) testing, multiplex ligation-dependent probe amplification (MLPA), or chromosomal microarray (CMA). All three are typically done from a blood sample and your genetic counselor or medical geneticist may choose one type of test or another based on your insurance and how strong the suspicion is of 22q11.2 deletion syndrome. Over 95% of people with a clinical presentation suggesting 22q11.2 deletion syndrome are able to receive a confirmation through genetic testing. A genetic counselor may be able to help facilitate genetic testing for you. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
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More Diagnosis and Testing Content

Is there newborn screening for 22q11.2 deletion syndrome?

Is there more than one test for 22q11.2 deletion syndrome?

Who else in my family should I test for 22q11.2 deletion syndrome?

Does it matter if you test blood vs. saliva vs. biopsy for 22q11.2 deletion syndrome?

Is there prenatal testing available for 22q11.2 deletion syndrome?

How accurate is the noninvasive prenatal testing (NIPT) blood test for 22q11.2 deletion syndrome?

Is there newborn screening for 22q11.2 deletion syndrome?

As of January 2014, 22q11.2 deletion syndrome is not on the Recommended Uniform Screen Panel (RUSP). The RUSP is created by the Health Resources and Services Administration, and states use this list to guide what conditions they screen for on newborn screening. There has been discussion about adding screening for 22q11.2 deletion syndrome to the RUSP, but was rejected in 2012. This may change in the future and we recommending consulting with your doctor for any updates.

Having said this, some states do test for Severe Combined Immunodeficiency (SCID) on their newborn screening panels. Due to the nature of the test, it may pick up children with 22q11.2 deletion syndrome who have immune issues at birth (not enough T lymphocyte cells). It is important to know that this test is not specifically looking for 22q11.2 deletion syndrome and thus not does detect all cases. To determine what conditions are on your state's newborn screen, please visit the Conditions Screened by State as part of the Baby's First Test website at https://www.babysfirsttest.org/newborn-screening/states.

Is there more than one test for 22q11.2 deletion syndrome?

There are a few genetic tests that can diagnose 22q11.2 deletion including fluorescence in situ hybridization (FISH) testing, multiplex ligation-dependent probe amplification (MLPA), or chromosomal microarray (CMA). FISH and MLPA testing are more targeted tests and test for 22q11.2 deletion only. A CMA looks for small deletions or duplication through all of a person's genetic information. Your healthcare provider, genetic counselor, and/or medical geneticist may choose one type of test or another based off of your insurance, the symptoms present, and how strongly they suspect 22q11.2 deletion syndrome. To further discuss these tests with a genetic counselors search the National Society of Genetic Counselors website.

References
Who else in my family should I test for 22q11.2 deletion syndrome?

If a new diagnosis of 22q11.2 deletion syndrome is made in a family, both parents should be offered testing for the condition, especially if one has any symptoms of 22q11.2 deletion syndrome. There is about a 7% chance that a person inherited the syndrome from a parent. Some labs routinely offer parental testing depending on the test ordered to see if genetic changes are inherited or occurred new in a child as well as to help with the interpretation of other genetic variants.

If a parent is identified with 22q11.2 deletion syndrome, all of their children should be offered testing for 22q11.2 deletion syndrome. Additionally your genetic counselor will help assess your family history to see if other individuals, such as parents or siblings, are at risk.

If neither parent has 22q11.2 deletion syndrome, we would believe that the condition occurred new in the one child and that the risk of other siblings to have the condition is less than 1%. That being said, the risk for siblings to have 22q11.2 deletion syndrome in this type of scenario is not 0%. This is because one parent may have a very low level of cells with 22q11.2 deletion syndrome that cannot be detected or that only their eggs or sperm have the deletion while the rest of the cells in their blood do not. In these instances, your genetic counselor or healthcare provider will ask in depth questions about the health and development of your other children to determine if they may have symptoms and if testing should be offered. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
  • McDonald-McGinn DM, Emanuel BS, Zackai EH. 22q11.2 Deletion Syndrome. 1999 Sep 23 [Updated 2013 Feb 28]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2016. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1523/
Does it matter if you test blood vs. saliva vs. biopsy for 22q11.2 deletion syndrome?

Though all three types of sample should give the same results, genetic testing for 22q11.2 deletion syndrome is most often done from a blood sample. Some labs may allow for a saliva sample to be submitted, but this is not usually the option they prefer.

Is there prenatal testing available for 22q11.2 deletion syndrome?

Prenatal diagnosis is available for 22q11.2 deletion syndrome should parents wish to test the fetus during the pregnancy. Testing is generally offered to couples known to have a higher chance to have a child with 22q11.2 deletion syndrome, for example if a parent has 22q11.2 deletion, or if a heart defect is identified on ultrasound. The two types of procedures that might be offered to get a DNA sample from the fetus include chorionic villus sampling (CVS) or amniocentesis. A prenatal genetic counselor can walk you through how each test is done, the benefits, risks, and limitations. As with any prenatal testing, such tests are optional. Genetic counselors can be found on the National Society of Genetic Counselors website.

Additionally, there is also preconception testing available for 22q11.2 deletion syndrome. Preimplantation genetic diagnosis (PGD) is a way to test embryos for a certain disorder before implantation. PGD is not a standalone test and has to be done as part of in-vitro fertilization (IVF). For more information on the option of PGD, please talk to a genetic counselor familiar with assisted reproductive technologies. A genetic counselor in the area can be found on the National Society of Genetic Counselor's "Find a Genetic Counselor" page of the website: http://nsgc.org/p/cm/ld/fid=164.

References
  • McDonald-McGinn DM, Emanuel BS, Zackai EH. 22q11.2 Deletion Syndrome. 1999 Sep 23 [Updated 2013 Feb 28]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2016. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1523/
How accurate is the noninvasive prenatal testing (NIPT) blood test for 22q11.2 deletion syndrome?

Noninvasive prenatal testing (NIPT) is a screening option for pregnant women, which gives a pregnant woman the option of having a blood test to determine the chances that the fetus has a chromosomal disorder. It was created to screen for Down syndrome, but many additional conditions have been added to the test including 22q11.2 deletion syndrome. Unfortunately, NIPT for 22q11.2 deletion syndrome is not as accurate as it is for Down syndrome. A 2015 study found a high number of false positives (80%) when testing fetuses for 22q11.2 deletion syndrome through NIPT. This implies that only 20% of the pregnancies with a positive result for 22q11.2 deletion syndrome actually had 22q11.2 deletion syndrome. Parents are recommended not to make decisions about the pregnancy solely based off of NIPT results. Diagnostic testing directly on a fetal DNA sample obtained with chorionic villus sampling (CVS) or amniocentesis can confirm or rule out 22q11.2 deletion syndrome accurately. More research needs to be conducted to better understand and improve the accuracy of NIPT for detection of 22q11.2 deletion syndrome.

If you have received a positive NIPT result for 22q11.2 deletion syndrome, talking to a prenatal genetic counselor may be beneficial as he/she can walk you through the risk of the result being a true positive based on the testing, your family history, and ultrasound findings. A genetic counselor can also discuss options for prenatal or post-delivery testing. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
  • Gross SJ, Stosic M, McDonald-McGinn DM, et al. Clinical Experience with Single-Nucleotide Polymorphism-Based Noninvasive Prenatal Screening for 22q11.2 Deletion Syndrome. Ultrasound in Obstetrics & Gynecology. 2015. [Epub ahead of print]

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