& Molecular Genetic
Studies in the Neonatal Period
|Reviewed by Salim
Note: Given the increasing concerns around
genetic testing without informed consent, only tests for diagnostic or
management reasons should be carried out in the neonatal period.
- Consultation with the Northern Regional Genetic Service is
recommended when further advice is needed (Ext. 25870 AKH)
- Confirmation of suspected chromosomal disorder following abnormal antenatal ultrasound undertaken late in pregnancy or where further investigation declined during in the pregnancy.
- Chromosome mosaicism found at CVS, amniocentesis or cordocentesis (where indicated)
- DNA studies. Cord blood confirmation of single gene disorder suspected on ultrasound findings eg achondroplasia
Testing for late onset disorders should not be undertaken
- Confirmation of biochemistry where prenatal diagnosis of a known condition undertaken (requested by testing lab)
- Clinical features consistent with known chromosomal abnormality.
- Multiple congenital anomalies consistent with possible chromosomal abnormality
- Ambiguous genitalia.
WHICH TEST TO REQUEST:
When the phenotype indicates a common aneuploidy (trisomy 21,
18, 13, or X aneuploidy) request a standard karyotype. If an
urgent result is required, specify “Rapid FISH Analysis” on
laboratory request form and identify the particular chromosome
in question (trisomy 21, 18, 13, X monosomy). Click
here for link to LabPlus test guide, for turnaround times.
In a baby with dysmorphism/abnormal neonatal adaptation/organ
anomalies where a specific diagnosis is not apparent: request a
standard karyotype (link to test guide).
If a specific diagnosis is unlikely to alter management,
consider an alternative request for a molecular karyotype (link
to test guide). If in doubt, please liaise with the clinical
geneticist on call.
Where the phenotype suggests a specific microdeletion syndrome,
particularly the 22q microdeletion syndrome, request the
specific FISH test (rapid test also available for urgent 22q
microdeletion requests, link to test guide).
N.B: If Prader-Willi syndrome is suspected, request the
methylation test for the 15q11.2-13 locus. For details on
turnaround times, please click here. If clinical suspicion is
high and a quicker result is desired, consider requesting the
specific FISH test, keeping in mind that deletions account for
65-75% of patients with PWS.
- Products of
- Post mortem - (1) -
(3) as above.
Guidelines for DNA Studies
in the Neonatal Period
- Features of a single gene disorder/syndrome (for diagnostic purposes)
- Mitochondrial myopathy syndrome.
- Features of possible single gene disorder where infant may die and genetic testing may later become available (DNA storage)
Blood Collection Tubes
- Chromosomes (conventional karyotype) and/or FISH (Lithium Heparin)
- Molecular Karyotype/Microarray (EDTA):
link to test guide
- Molecular Genetic/DNA studies (EDTA)