Use of test
Chromosome analysis can detect balanced and unbalanced rearrangements, and numerical changes of autosomes and sex chromosomes.
Once a potential abnormality is identified, chromosome studies of parents may be necessary to clarify the genetic diagnosis and the risks to relatives.
In an affected person, an abnormal result usually provides a genetic diagnosis and the basis for genetic counselling. A normal result does not exclude a genetic or heritable basis for the disorder as sub-microscopic changes would not be detected.
This is an assay for mutations which may be heritable or de novo. It may raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient. Use of the consent form (below) is not mandated, but could be used to guide the discussion with the patient.
In the case of carrier testing of an unaffected child, national regulations require that the laboratory has evidence of pre-test counselling by a genetics professional and written consent.
Link to Sonic Genetics consent form.
Analysis of metaphase chromosomes by light microscopy. Chromosomes are counted and examined for structural and numerical abnormalities.
Requesting the Test
This test can be requested by any medical practitioner.
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.
Please include details of any clinical abnormalities in the patient being tested, and the results of chromosome or array studies in relatives.
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 73289.