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Fragile X (FMR1) with Reflex to Methylation Analysis, Fetal
2009034
Ordering Recommendation

Prenatal test for fetuses of mothers with fragile X premutations or full mutations.

Mnemonic
FX PCR FE
Methodology
Polymerase Chain Reaction/Capillary Electrophoresis
Performed
Sun-Sat
Reported
Within 10 days
New York DOH Approval Status
This test is New York DOH approved.
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
 
Collect
Fetal Specimen: Amniotic fluid or two T-25 flasks at 80 percent confluency of cultured amniocytes. If the client is unable to culture amniocytes, this can be arranged by contacting ARUP Client Services at (800) 522-2787.
AND Maternal Specimen
: Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B). 
Specimen Preparation
Amniotic Fluid: Transport 10 mL unspun fluid. (Min: 5 mL)
Cultured Amniocytes: Fill flasks with culture media. Transport four T-25 flasks at 80 percent confluency of cultured amniocytes. Backup cultures must be retained at the client's institution until testing is complete.
Maternal Specimen:
Transport 3 mL whole blood. (Min: 1 mL) 
Storage/Transport Temperature
Amniotic Fluid: Room temperature.
Cultured Amniocytes: CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to viability of cells.
Maternal Specimen: Room temperature. 
Unacceptable Conditions
 
Remarks
Maternal specimen is recommended for proper test interpretation. Order Maternal Cell Contamination, Maternal Specimen. This can be arranged by contacting ARUP genetic counselors at (800) 242-2787 ext. 2141. Patient History Form is available on the ARUP Web site or by contacting ARUP Client Services at (800) 522-2787. 
Stability
Fetal Specimen: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Maternal Specimen
: Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable 
Reference Interval
By report
Interpretive Data
Background information for Fragile X (FMR1), Fetal
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:
Triplet repeat-primed polymerase chain reaction (PCR) followed by size analysis using capillary electrophoresis. Methylation-specific PCR analysis is performed for CGG repeat lengths of 55 or greater. Methylation analysis is used to distinguish between premutation and full mutation alleles.
Analytic Sensitivity and Specificity:
99 percent
Limitations:
Diagnostic errors can occur due to rare sequence variations.

For quality assurance purposes, ARUP Laboratories will confirm the above result at no charge following delivery. Order Confirmation of Fetal Testing and include a copy of the original fetal report (or the mother's name and date of birth) with the test submission. Please contact an ARUP genetic counselor at (800) 242-2787 extension 2141 prior to specimen submission.

PhenotypeNumber of CGG Repeats
Unaffected<45
Intermediate45-54
Premutation55-200
Affected>200

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.

Note
If a CGG repeat of 55 or greater is detected by PCR and Capillary Electrophoresis; methylation analysis will be added. Additional charges apply.
CPT Code(s)
81243; 81265; if reflexed add 81244
Components
Component Test Code*Component Chart NameLOINC
0050548Maternal Contamination Study Fetal Spec59266-7
0050556Fragile X Allele 145321-7
0050558Fragile X Allele 245322-5
0050559Fragile X Methylation Pattern41107-4
0050612Maternal Contam Study, Maternal Spec31208-2
0051389Fragile X Fetal Specimen
2010041Fragile X Interpretation, Fetal
* 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.
Aliases
  • Cytogenetics, High Resolution & Fragile X DNA (Fragile X (FMR1) Diagnostic, Fetal)
  • High Resolution & Fragile X DNA (Fragile X (FMR1) Diagnostic, Fetal)
  • Inherited Mental Retardation (Fragile X (FMR1) Diagnostic, Fetal)
  • Martin-Bell Syndrome (Fragile X (FMR1) Diagnostic, Fetal)