Trisomy 4p

Diagnosis and Testing

How do I get tested for trisomy 4p?

The main test used to diagnose trisomy 4p is called a karyotype or chromosomal analysis. This test provides a picture of the chromosomes (instructions that tell the body how to grow and develop). A karyotype lets your healthcare team see if there is an extra chromosome 4p in the cells. Karyotypes can be performed on blood cells or other cells of the body. Prenatal diagnosis for trisomy 4p can also be performed by amniocentesis or CVS (chorionic villus sampling).

Another test which can diagnose trisomy 4p is a comparative genomic hybridization (cgh) microarray also known as a "microarray" or "chromosomal microarray". A microarray is a method of studying all of person's DNA in one test. In this test, many small probes are used to determine if there are any extra or missing pieces of DNA. The patient sample that is being tested is compared to a reference or control sample. A computer reads the information from the test and tells scientists if there is more or less DNA present from the patient than from the reference sample. If there is more patient DNA, then the patient may have extra DNA, called a duplication. If there is less DNA from the patient, the patient may have a missing DNA, called a deletion. The microarray can detect smaller gains or losses of DNA that a karyotype can, but it cannot detect mutations within a specific gene that do not result in missing or added genetic information. Having said this, microarrays are used to look at specific genes for added or lost DNA when a genetic sequence test comes back negative in a person who appears to have a specific genetic condition.

To find a genetic professional near you who is experienced in discussing and ordering karotyping and microarray testing, visit one of the following two sites: American College of Medical Geneticists website (www.acmg.net) and the National Society of Genetic Counselors website: www.nsgc.org.

References
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More Diagnosis and Testing Content

Is there newborn testing for trisomy 4p?

Is there more than one test for trisomy 4p?

Does it matter if you test blood vs. saliva vs biopsy for trisomy 4p?

Who else in my family should I test for trisomy 4p?

Is there newborn testing for trisomy 4p?

This condition is not included in the newborn screen that is given to all new babies. If trisomy 4p is suspected, the doctor can order either a karyotype or a chromosomal microarray to determine if there is extra chromosome 4p in the cells. Testing is usually done on a blood sample.

Is there more than one test for trisomy 4p?

There are two types of testing that can confirm the diagnosis of trisomy 4p. The is called a karyotype or chromosome analysis. This is a picture of the chromosomes (the instructions that tell the body how to grow and develop).

Another test which can diagnose trisomy 4p is a comparative genomic hybridization (cgh) microarray also known as a "microarray" or "chromosomal microarray". A microarray is a method of studying all of person's DNA in one test.

Both of these tests let doctor see if there is an extra chromosome 4p in the cells.

If a diagnosis is made, there may be more tests to look for symptoms. For example, an echocardiogram is an ultrasound that looks at the heart, an MRI (magnetic resonance imaging) looks at organs like the brain, and an x-ray looks at bones. An EEG (electroencephalography) might also be done to see if a person is likely to have seizures.

Does it matter if you test blood vs. saliva vs biopsy for trisomy 4p?

DNA testing is usually done on a blood sample.

Who else in my family should I test for trisomy 4p?

If a child is born with trisomy 4p, it is important to order a genetic test on the parents. There might be a change in the parents' genetic information that makes it more likely that their children will have trisomy 4p. Check with your doctor if you have questions about who in your family should be tested. A genetic counselor can talk to you about this test and help to order it. To find a genetic counselor near you, use the "Find a Genetic Counselor" tool on the National Society of Genetic Counselors' website.

References

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