Fragile X carrier screening (FMR1 repeat analysis)

Test code



3 mL amniotic fluid or 20 mg chorionic villi or 3 mL EDTA blood


Sterile plastic conical tube or Sterile plastic conical tube with transport medium or Purple-top (EDTA) tube

Special instructions




Causes for rejection

Frozen specimen; specimen found not to be amniotic fluid; gross contamination with red cells; nonsterile container

Description of analysis

This test examines the expansions of CGG tri-nucleotide repeat in the 5'-untranslated region (UTR) of the Fragile X Mental Retardation-1 (FMR1) gene on X chromosome. These expansions are associated with several disorders, including fragile X syndrome and fragile X-associated tremor/ataxia

Test methodology

Specific PCR amplification followed by capillary electrophoresis size analysis is used to determine the size of the amplified products

Test methodology

Mental retardation associated with other Fragile X sites, in particular Fragile XE or other gene mutation will not be detected

Storage instruction

Specimen should be kept at room temperature


American college of medical genetics guidelines for clinical genetics laboratories (2006)


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