How is it used?
Testing is performed when a person has intellectual disability, ataxia ( i.e. when you have trouble moving parts of your body the way you want, and your arms and legs may move when you don't want them to), neurodegeneration ( the progressive loss of neurones from the brain), or premature ovarian failure and infertility.
When is it requested?
Testing is requested by the doctor when it is suspected that the clinical signs are due to Fragile-X.
What does the test result mean?
If the number of CGG repeats is in the range of 5 to 44 CGG, this is considered a normal result. If the repeats are in the size range of 55 to 200 CGG repeats this is a pre-mutation result and if the repeat size is greater than 200 CGG repeats, this is a full mutation and the person has Fragile-X.
Is there anything else I should know?
Although current guidelines still make reference to Southern blot analysis, the test is subjective, compared with more objective newer methods. Southern blotting is technically complex, expensive, laborious to perform and requires a large quantity of DNA for testing. Newer methods are therefore replacing Southern blotting, for example, a triplet repeat primed PCR assay followed by high-thoughput automated capillary electrophoresis to detect the number of CGG repeats is now widely used. As a result there has been a decline in the proportion of patients in whom Southern blot analyses is being performed.