Developmental Disorders
For congenital disorders, developmental delay, learning difficulties, etc.
ArrayCGH – gold standard test for chromosomal abnormalities
– aneuploidy (e.g. Down syndrome)
– traditional chromosome analysis
– single gene diseases
Chromosome analysis or arrayCGH?
If the physician is confident the child has an aneuploidy (abnormal number of chromosomes, e.g. Down syndrome), chromosome analysis is the best frontline test – it is cheaper and faster.
However, if it is not an aneuploidy, but is instead a smaller genetic imbalance, this is likely to be missed by chromosome analysis, and further testing in the form of arrayCGH would then be required.
Chromosome analysis requires a blood sample in a green top tube.
If the phenotype may be due to a deletion or duplication of part of a chromosome, arrayCGH is the best frontline test – it looks at the chromosomes at much higher resolution and therefore can detect imbalances on a gene level. It is more expensive, and the result takes a little longer, but it is a much more comprehensive test. It is the gold standard test for developmental disorders. If it is an aneuploidy, this will still be detected by arrayCGH.
ArrayCGH requires a blood sample in a purple top tube.
If an abnormality is found, parental samples may be recommended, to check for any reoccurrence risk. Depending on what is found, this might be by chromosome analysis or arrayCGH.
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