Use of test
Microarray analysis can detect submicroscopic deletions and duplications of genetic material across all chromosomes.
In the first instance, this test is for an affected patient and can provide diagnostic and prognostic information. Once a potential abnormality is identified, studies of relatives may be necessary to clarify the genetic diagnosis and the risks to relatives.
The presence of a pathogenic abnormality provides specific diagnostic and prognostic information. Further family studies may clarify the recurrence risk in relatives.
The absence of a pathogenic abnormality does not necessarily exclude a clinical diagnosis.
Microarrays can also detect deletions and duplications that are of unknown clinical significance or which have variable clinical outcomes. Rarely, deletions or duplications which are associated with a clinically significant disorder unrelated to the presentation of the patient may be detected. The report will provide advice regarding the interpretation of such findings.
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.
Download the Sonic Genetics consent form.
The relative amounts of genetic material from hundreds of thousands of small regions from all chromosomes are measured. Deviations from the expected values can identify deletions and duplications.
Sonic Genetics uses a single nucleotide polymorphism (SNP) microarray, which provides additional genotype information compared with CGH microarray. SNP microarrays can identify large regions of homozygosity, which may be useful in detecting uniparental disomy or an increased likelihood of a recessive disorder.
Requesting the test
This test can be requested by any medical practitioner.
2-5 mL blood in EDTA or lithium heparin. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare collection centre (see link below).
Buccal swabs are available on request, please contact the laboratory if this method of collection is required.
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. If the patient is not eligible for rebated testing, please contact your local Sonic pathology practice for pricing.
The Medicare details, including descriptor and schedule fee, are listed under MBS 73292.