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 These tests have superseded chromosome or karyotype tests.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 this bit of DNA does this child have?). Microarray testing are used to diagnose approximately 15% of children without a genetic diagnosis. The turnaround time for this test is approximately three to five weeks. Parents/carers who have a child with syndromic features and no diagnosis may want to consider having one performed.
Whole genome sequencing
Whole Genome Sequencing (also known as exome sequencing, next-gen sequencing) is a new test where you have all the genes in their body sequenced (which means spelled out). It is not a test for dosage (i.e. how many copies) but is looking for “spelling mistakes”. For example if a gene should read AGGTC, but actually reads AGTTC, this would be picked up by whole genome sequencing, not by microarray testing.
This test has been introduced in clinical practice in some states of Australia as some states establish an Undiagnosed Children’s Disease program. Genome sequencing is likely to help us get answers for maybe 30 to 50% of children without a diagnosis, so is very exciting, but because it spells out every gene, it can give information that perhaps individuals didn’t want to know, such as gene mistakes that can cause adult-onset diseases like cancer and Alzheimers disease. Doctors and scientists are currently trying to design filters so we can learn about all the genes we want to know about and filter out the information most families would prefer not to know about.