Also known as: 22q FISH, 22q11.2 deletion syndrome, DiGeorge syndrome, velocardiofacial syndrome (VCFS), conotruncal anomaly face syndrome (CTAF), Opitz G/BBB syndrome, Cayler cardiofacial syndrome, Shprintzen syndrome, CATCH22
Paediatric - Congenital disorder
Use of test
Deletions of the proximal long arm of Chromosome 22 (22q) cause a characteristic syndrome of developmental delay and malformations. The syndrome is called DiGeorge syndrome (DGS) or velo-cardio-facial syndrome (VCFS). The deletion may be too small to be seen by conventional chromosome studies. This test provides diagnostic information.
In an affected person, an abnormal result is diagnostic of this microdeletion syndrome. Further family studies may clarify the recurrence risk in relatives.
A normal result makes it unlikely that the patient has this disorder.
These mutations are often de novo and do not increase the risk of this disorder in siblings or other relatives. However a parent and other relatives may have the same deletion (and lack obvious features of the disorder) and yet be at risk of having an affected child.
Fluorescent in situ hybridisation (FISH) analysis using probes located within 22q. Deletions that are smaller than the probe may not be detected.
Requesting the test
This test is usually requested by a paediatrician or clinical geneticist. A full karyotype is usually requested at the same time.
2-5 mL blood in EDTA and 2-5 mL blood in lithium heparin. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare collection centre (see link below).
To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.
We recommend that the patient or another adult check the labelling of request forms and sample tubes.
If the clinical diagnosis is uncertain, it may be preferable to request a microarray study rather than this specific FISH test as a microarray screens for microdeletions and duplications across all chromosomes.
5 business days.
This test has a Medicare rebate which, subject to the requirements of the Medicare descriptor being met, may cover all or part of the cost.
The Medicare details, including descriptor and schedule fee, are listed under MBS item 73291.