Fragile X Syndrome

Order Code:  332122

CPT Codes:  81243, 81244*, G0452

*81244 (Southern blot) will be billed only when:

PCR identifies an allele size ≥55 CGG repeats

Indication:  Carrier Screening; Clinical Diagnosis or Prenatal testing

Required Patient Information:  Personal and Family History of clinical symptoms and/or previous test results (if any); For prenatal testing: LMP date or gestational age at the time of sample collection

Turn Around Time for PCR:  7-14 days

Turn Around Time for Southern Blot: 21 days

Specimen type: Whole Blood, Amniotic Fluid, Chorionic Villi*

*Chorionic villi will be accepted for PCR only; it is not a reliable sample for Southern blot analysis

Methodology: A single tube CGG repeat primed PCR based assay using two gene-specific primers that flank the triplet repeat along with a third primer that is complementary to the (CGG)n repeat is used to determine genotypes for CGG allele sizes within the Fragile X gene (FMR1). This assay will identify alleles of all sizes but cannot determine methylation status of expanded alleles.  Reflex to a Southern blot assay will be performed for all samples with an allele size ≥55 CGG repeats, to determine methylation status. 

Other Requirements: A maternal blood sample is required for all prenatal specimens.