Our Tests

Williams Syndrome FISH

Also known as: Williams Syndrome FISH, 7q11.23 FISH

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Deletion of genes on the long arm of chromosome 7 (7q) can cause a characteristic syndrome of abnormal neurodevelopment and malformations (Williams syndrome). This test provides diagnostic information.

These mutations are usually de novo and do not increase the risk of this disorder in siblings or other relatives. However a parent and other relatives may carry a balanced translocation involving this chromosome region and be at increased risk of having an affected child.

Clinical Utility

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 does not exclude a clinical diagnosis as there are other mutations on chromosome 7 which can cause the syndrome.



Test Method

Fluorescent in situ hybridisation (FISH) analysis using probes located on the long arm of chromosome 7.

Test Ordering

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 lithium heparin. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare pathology collection centre.

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 also recommend that the patient or another adult check the labelling of request forms and sample tubes.

Special Instructions

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.



This test may have a rebate for all or part of the cost.

Medicare Rebate

This test has a Medicare rebate of $196.35, subject to the requirements of the Medicare descriptor being met. The MBS item number is 73291.

Turnaround Time

15 working days for karyotype and FISH study; 3 working days for FISH alone.