Fragile X carrier screening (FMR1 repeat analysis)

GFS

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

Nil

Nil

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

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

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

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

Specimen should be kept at room temperature

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