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 15-20 ml. Discard the first 2 ml of fluid to reduce the risk of maternal cell contamination. Aseptically transfer the specimen into sterile plastic conical tubes labeled with patient’s name and date of birth.
- CVS 10-20 mg. Aseptically transfer the specimen into sterile plastic conical tubes containing sterile transport medium. Label tube with patient’s name and date of birth.
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 STAT 24-hour study on interphase cells followed by complete Cytogenetic analysis
Transport Temperature
Room temperature (DO NOT refrigerate, freeze or centrifuge)
Methodology
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