+21, CEP 21
Fluorescence in situ Hybridization (FISH)
*Performed by affiliate laboratory
5mL peripheral blood in sodium heparin
3mL bone marrow in sodium heparin
Fixed cytogenetically prepared cells in sterile centrifuge tube with pellet visible in 3:1, Methanol:Acetic Acid
4°C to 25°C during transit, but specimens may be transported on refrigerated gel packs. Do not allow the gel pack to come in contact with the specimen. Do not freeze. Extreme temperatures should be avoided.
Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; Insufficient number of cells
Conventional cytogenetic evaluation is required for prenatal and newborn cases when aneuploidy FISH is requested (typically chromosomes X,Y,13,18 and 21). If the FISH result is abnormal, chromosome analysis can determine whether the abnormality is due to aneuploidy or a complex structural abnormality and will enable a more accurate recurrence risk for the family. If the FISH result is normal, a chromosome analysis allows identification of more complex abnormalities and the less common numeric abnormalities of other chromosomes.
An extra copy of chromosome 21 is the cause of Down syndrome. An increase risk is seen with the increase in maternal age.