Down syndrome (trisomy 21)

Indications For Down Syndrome (trisomy 21)
Down syndrome is caused by the presence of an additional copy of all or a portion of chromosome 21. Trisomy 21 is typically associated with delays in physical growth, characteristic facial features, and mild to moderate intellectual disability.  Additional health problems, include congenital heart disease, increased risk of leukemia, thyroid disorders, and mental illness.

Collection Procedure
•    Amniotic fluid
Discard the first 2 cc of fluid to reduce the risk of maternal cell contamination.  Aseptically transfer 15-20 cc into sterile plastic conical tubes labeled with patient’s name and date of birth.
•    CVS
Aseptically transfer 5-10mg into sterile plastic conical tubes containing sterile transport medium.  Label tube with patient’s name and date of birth.
•    Peripheral blood
Collect 5-10 cc whole blood in a green top tube (sodium heparin).  Label tube with patient’s name and date of birth. (laboratory testing on newborn babies suspected to have Down syndrome require 1-2 cc)

A completed test requisition form must be included with every sample.  A transport kit is available upon request.

Specimen Requirements
FISH analysis can be performed as a SAT 24 hour study on interphase cells followed by complete CytoGenetic analysis

Transport Temperature

Room temperature (DO NOT refrigerate, freeze or centrifuge)


24-hour laboratory testing for Down syndrome can be performed by Fluorescence in situ hybridization on interphase nuclei followed by confirmatory cytogenetic analysis.

Causes for Rejection

Frozen specimen, inappropriate container

Turnaround Time

FISH: 24 hours

Cytogenetic analysis: 7-10 days