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FISH for Microdeletion or Microduplication Syndromes


Molecular cytogenetic studies using fluorescence in situ hybridization (FISH) focus on deletions and duplications of specific chromosomes and chromosomal regions.

Studies are indicated in patients with clinical features associated with specific syndromes involving the loss or gain of small amounts of chromosomal material, often too small to be detected by chromosome analysis.

FISH probes specific for the critical regions involved in the following syndromes have been developed:


  • ​​Deletion/Duplication 22q11.2
  • ​15q duplication
  • ​Prader Willi/Angelman
  • ​Williams
  • ​Cri-du-Chat
  • Steroid sulfatase deficiency
  • ​SRY deletions




FISH studies involve analysis of hybridization signals using chromosome-specific DNA probes on metaphase spreads or interphase nuclei.

Chromosome studies are performed concurrently with FISH testing, if they have not been done previously. 


Specimen Requirements

If FISH is done in conjunction with chromosome analysis, no additional specimen is usually required.

If FISH is requested at a later date subsequent to chromosome analysis, call CGL to determine if we still have enough sample on which the test can be performed.  If not:

    • Submit 3 ml peripheral blood in a 3 cc sodium heparin, green top tube.
    • Label specimen tube with patient’s name and a second identifier (ex: DOB, hospital ID)
    • Maintain specimen at room temperature and transport to the Colorado Genetics Laboratory immediately.

Other specimen types may be submitted. Please contact CGL  for more information.

Samples must be accompanied by a completed Test Request Form​​, including pertinent clinical and family history.