SNP Microarray (commonly called ‘snip array’) and genomic microarray test is the same common genetic test for children with syndromic features without a diagnosis. These tests have superseded chromosome or karyotype tests.
Microarray testing measures dosage. (i.e. how many copies of their bit fo DNA does this child have). Microarray testing are used to diagnose approximately 15% of children without a genetic diagnosis. Th turns round time for this test is approximately 3-5 weeks. Parents who have a child with syndromic features and no diagnosis may want to consider having this test.
Whole genome sequencing
Whole Genome Sequencing (WGS) is a relatively new test where all the protein coding genes (around 20,000) in the body are sequenced (the genes are spelt out to try and find the spelling mistake). It is not a test for a dosage (i.e. how many copies) but a test that looks for “spelling mistakes in the genetic code”. For example if a gene should read AGTC, but actually reads AGCT, this would be picked up by whole genome sequencing but not a microarray test.
This test has been introduced into clinical practise in some states of Australia but due to funding is not offered in every genetics clinic on a clinical basis. Genome sequencing is likely to help us get answers for 30-50% of children who are currently undiagnosed. However with this technology comes the possibility of incidental findings (learning about a disease/condition that you may develop in the future). These may be identified unless some filters are applied to filter out the information families may not wish to know about.