Fragile X (FMR1) with Reflex to Methylation Analysis
2009033
Ordering Recommendation
Preferred test to diagnose fragile X syndrome in individuals with characteristic clinical symptoms or screen healthy individuals for carrier status with or without a positive family history.
Mnemonic
FRAG X PCR
Methodology
Polymerase Chain Reaction/Capillary Electrophoresis
Performed
Sun-Sat
Reported
4-14 days
New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
 
Collect
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
 
Remarks
Patient History Form is available on the ARUP website or by contacting ARUP Client Services.  
Stability
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable  
Reference Interval
By report
Interpretive Data
Background Information for Fragile X (FMR1)
Characteristics:
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/Capillary Electrophoresis. Methylation analysis is performed to distinguish between premutation and full mutation alleles.
Analytic Sensitivity and Specificity:
99 percent
Limitations:
Diagnostic errors can occur due to rare sequence variations.



Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.

See Compliance Statement C: www.aruplab.com/CS
Phenotype Number of CGG Repeats
Unaffected <45
Intermediate 45-​54
Premutation 55-​200
Affected >200
Note
If an intermediate to expanded allele (CGG repeats) is detected by PCR and Capillary Electrophoresis; methylation analysis will be added to determine the size of the expanded CGG repeat. Additional charges apply.
CPT Code(s)
81243; if reflexed add 81244
Components
Component Test Code*Component Chart Name
0050556Fragile X Allele 1
0050558Fragile X Allele 2
0050559Fragile X Methylation Pattern
0050579Fragile X Interpretation
2001310FRAG X Specimen
* 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.
Cross References
  • Inherited Mental Retardation (Fragile X (FMR1) Diagnostic)
  • Martin-Bell Syndrome (Fragile X (FMR1) Diagnostic)