Testing for FXS

Although there is currently no cure for fragile X syndrome, diagnostic testing is important because there are many management and intervention strategies available to help the affected person reach his or her full potential.

Fragile X syndrome is diagnosed by a simple DNA blood test. In contrast to the earlier unreliable cytogenetic test, the DNA test is over 99% accurate.

The test is recommended for: 

  • Anyone with an intellectual disability (borderline to severe) of unknown cause 
  • Anyone previously tested with the unreliable cytogenetic test, especially people with an intellectual disability for whom the test was negative or inconclusive 
  • Anyone with a confirmed family history of fragile X syndrome who could have inherited the mutant gene, especially women considering having children
  • Siblings of a child diagnosed with fragile X syndrome should be tested automatically to rule them out
  • Anyone with learning difficulties of unknown cause and emotional or behavioural features of fragile X (including autistic features, anxiety syndromes and ADHD) 
  • Women who experience premature menopause (menopause before the age of 40 years) 
  • Adult males (>50 years of age) who present with unexplained ataxia and/or essential tremor, parkinsonism and dementia

Chromosomal Microarray Analysis and the DNA Test for Fragile X

Chromosomal microarray analysis is a powerful test for detecting certain genetic causes of developmental disabilities; however, it is not able to detect fragile X mutations of any kind. For this reason, the diagnostic work-up of children with autism, global developmental delay, or intellectual disabilities should include both a microarray analysis and a separate fragile X DNA analysis. If your child just had the microarray analysis but not the specific DNA test for fragile X, then he has not been checked for fragile X. 

In New Zealand, fragile X testing is carried out by Genetic Health Services New Zealand (GHSNZ), which has offices in Auckland, Wellington and Christchurch. They can be contacted as follows:

Genetic Health Service NZ – Northern Hub
Auckland Hospital
Private Bag 92 024
Auckland Mail Centre
Auckland 1142

Ph: (09) 307 4949 Ext. 25870
Toll Free: 0800 476 123
Fax: (09) 307 4978
Email: GenSec@adhb.govt.nz

Genetic Health Service NZ – Central Hub
Wellington Hospital
Private Bag 7902
Wellington South

Ph: (04) 385 5310
Toll free: 0508 364 436
Fax: (04) 385 5822
Email: genetic.services@ccdhb.org.nz

Genetic Health Service NZ – South Island Hub
Christchurch Hospital
Private Bag 4710
Christchurch 8140

Ph: (03) 378 6574
Toll free: 0508 364 436
Fax: (03) 379 1343
Email: genetic.servicenz@cdhb.health.nz 

More detailed information can be found under “Testing” on the US National Fragile X Foundation website.

The Human Genetics Society of Australasia website has the key policy documents (pdf file; requires Acrobat Reader, which can be downloaded at this link) that guide New Zealand practice on testing for fragile X syndrome.

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