Indications for testing for Edwards syndrome (trisomy 18)
Trisomy 18 or Edwards Syndrome is a genetic disorder caused by the presence of an extra copy of all or part of chromosome 18.
In utero, the most common characteristics are:
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.
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)
Methodology
24-hour laboratory testing for Edwards 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
