ARUP's Laboratory Test Directory

Fragile X (FMR1) Diagnostic, Fetal : 0050543
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Time Sensitive
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Patient History for Fetal Molecular Testing


Mnemonic: FRAG X FE

Ordering Recommendation: Diagnostic testing for fragile X syndrome.
Methodology: Southern Blot/Polymerase Chain Reaction/Fragment Analysis
Performed: Sun-Sat
Reported: Within 10 days
Specimen Required: Collect: Fetal Specimen: Four 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. Or amniotic fluid. Amniotic fluid submissions will require cultured amniocytes (Order Amniocyte Culture, Four Flask).
AND Maternal Cell Contamination Specimen: Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).

Specimen Preparation: 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.
OR Amniotic Fluid: Transport 10 mL unspun fluid. (Min: 5 mL)
AND Maternal Cell Contamination Specimen: Transport 3 mL whole blood. (Min: 1 mL)

Storage/Transport Temperature: Cultured Amniocytes: CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to viability of cells.
Amniotic fluid: Room temperature.
Maternal Cell Contamination Specimen: Room temperature.

Remarks: Maternal specimen is recommended for proper test interpretation. Order Maternal Cell Contamination. Patient History Form is available on the ARUP Web site or by contacting ARUP Client Services.

Stability (collection to initiation of testing): Fetal Specimen: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Maternal Cell Contamination Specimen: Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Reference Interval:
By report
Interpretive Data: Fragile X (FMR1) Diagnostic, 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: 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.

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.



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

CPT Code(s): 81244; Fetal Cell Contamination (FCC): 81265
Cross References: 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)