Edwards syndrome (Trisomy 18)

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 characteristic are
cardiac anomalies
central nervous system anomalies
choroid plexus cysts

All infants born with Edwards syndrome present with
kidney malformations
Structural heart defects
Esophageal atresia
Mental retardation
Developmental delays
Growth deficiency
Feeding difficulties
Breathing difficulties

Some other physical findings (symptoms) may include:

Short breast bone
Clenched hands
Underdeveloped thumbs and or nails
Absent radius
Webbing of the second and third toes
Clubfoot or Rocker bottom feet
Undescended testicles in males.

Facial Features
Microcephaly accompanied by a prominent back portion of the head
Low-set, malformed ears
abnormally small jaw (micrognathia)
Cleft lip/cleft palate
Upturned nose
Narrow eyelid folds (palpebral fissures)
Widely-spaced eyes (ocular hypertelorism)

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)

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