What is Fluorescent in situ hybridization FISH DNA test?
Fluorescence In-Situ Hybridization is a method used to identify specific parts of a chromosome. FISH can be used to detect small deletions and duplications that are not visible using microscope analysis like karyotyping. It can also be used to detect how many chromosomes of a certain type are present in each cell and to confirm rearrangements that are suspected after microscope analysis.
This method looks specifically at the one specific area of a chromosome only. The fluorescent
chemical that glows brightly when it detects the specific region on a chromosome. A scientist uses a special microscope to look at the chromosome and see how many bright spots are present. When a person has a deletion, only one bright spot can be seen instead of two (one on each chromosome). When a person has a duplication, three bright spots can be seen instead of just two.
Why has FISH been recommended for the child?
FISH is often performed alongside standard microscope analysis if your child has characteristics that are strongly suggestive of a particular deletion syndrome or another syndrome for which a FISH test is available. Your Physician may request microscope analysis and FISH testing together or may request FISH testing if microscope analysis gives a normal result.
What samples are needed for FISH testing?
FISH is most commonly performed on blood samples from adults and children. FISH can also be used as a prenatal test for aneuploidy (extra copies of whole chromosomes) using amniotic fluid from an amniocentesis or placental samples from chorionic villus sampling (CVS). Less commonly it is used as a prenatal test for deletions, also using amniotic fluid or CVS samples.