Fragile X (FMR1) Diagnostic (INACTIVE as of 01/06/14. Refer to 2009033)
Ordering Recommendation
Southern Blot/Polymerase Chain Reaction/Fragment Analysis
4-14 days
New York DOH Approval Status
This test is New York DOH approved.
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B). 
Specimen Preparation
Transport 5 mL whole blood. (Min: 1.5 mL) 
Storage/Transport Temperature
Room temperature. If transport time will exceed 48 hours: Refrigerated. 
Unacceptable Conditions
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable 
Reference Interval
By report
Interpretive Data
Fragile X (FMR1) Diagnostic
Fragile X syndrome, the most common heritable form of mental retardation, is characterized by moderate mental retardation in males and mild mental retardation in females, hyperactivity, perseverative speech, social anxiety, poor eye contact, hand flapping or biting, autism spectrum disorders behavioral phenotype, and connective tissue anomalies. Adult males may have physical findings including: macroorchidism, a long narrow face, prominent ears and jaw, and a single palmar crease.
Incidence: 1 in 4,000 Caucasian males and 1 in 8,000 Caucasian females; unknown in other ethnicities
Inheritance: X-linked dominant.
Penetrance: Reduced in females.
Cause: Expansion of the FMR1 gene CGG triplet repeat.
Full mutation:>200-230 CGG repeats (methylated)
Premutation: 55-200 CGG repeats (unmethylated)
Intermediate: 45-54 CGG repeats (unmethylated)
Normal: 5-44 CGG repeats (unmethylated)
Clinical Sensitivity: 99 percent.
Methodology: PCR and Southern blot hybridization. Methylation analysis is performed to distinguish between premutation and full mutation alleles. The sex chromosome gene amelogenin is used to confirm gender but also may indicate the possibility of X chromosome aneuploidies such as Klinefelter or Turner syndrome.
Analytic Sensitivity and Specificity: 99 percent
Limitations: Analytic sensitivity may be compromised by PCR primer site mutations. Diagnostic errors can occur due to rare sequence variations.

Number of CGG Repeats

Compliance Statement C: The performance characteristics of this test were validated by ARUP Laboratories. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test. However, FDA approval or clearance is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. ARUP is authorized under Clinical Laboratory Improvement Amendments (CLIA) and by all states to perform high-complexity testing. Counseling and informed consent are recommended for genetic testing. Consent forms are available online.

CPT Code(s)
Component Test Code*Component Chart NameLOINC
0050556Fragile X Allele 145321-7
0050558Fragile X Allele 245322-5
0050559Fragile X Methylation Pattern41107-4
0050579Fragile X Interpretation36913-2
2001310FRAG X Specimen66746-9
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
  • FMR1
  • Fragile X tremor ataxia syndrome
  • Inherited Mental Retardation
  • Martin-Bell Syndrome