ARUP's Laboratory Test Directory

Fragile X (FMR1) Screen with Reflex to Fragile X (FMR1) Diagnostic : 2001946
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Patient History For Molecular Genetic Testing
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Additional Technical Information


Mnemonic: FRAG X SCR

Ordering Recommendation: Carrier screening for fragile X syndrome.
Methodology: Polymerase Chain Reaction/Fragment Analysis
Performed: Varies
Reported: 7-10 days
Specimen Required: Patient Prep: For buccal collection, the patient should not eat, drink, smoke, or chew gum for 30 minutes before collecting oral samples.

Collect: Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B). Or, one buccal sponge using the ORAcollect™collection kit (ARUP supply #49295)

Specimen Preparation: Transport 3 mL whole blood. (Min: 3 mL); or, one buccal sponge in the ORAcollect™collection kit.

Storage/Transport Temperature: For whole blood, ship refrigerated. For buccal sponge, ship at room temperature.

Remarks: Use only the ORAcollect™kit for buccal sampling. Other buccal collection devices (e.g., swab) are not acceptable for testing.

Stability (collection to initiation of testing): Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Reference Interval:
Test Number Components Reference Interval
Fragile X (FMR1) Mutation Screen By report
0040011Fragile X (FMR1) Diagnostic By report

Interpretive Data: Background Information for Fragile X (FMR1) Screen:
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, behavioral phenotype, connective tissue anomalies, and physical findings. Older male premutation carriers may develop fragile X-associated tremor/ataxia syndrome (FXTAS) characterized by progressive cerebellar ataxia and intention tremor. Female premutation carriers may develop premature ovarian insufficiency (20 percent), or rarely, FXTAS.
Incidence of Disease: 1 in 4000 males and 1 in 8000 females.
Incidence of Premutation: 1 in 1000 males and 1 in 350 females.
Inheritance: X-linked dominant.
Penetrance: Reduced in females.
Cause: CGG expansions in the 5' untranslated region of FMR1 leading to hypermethylation of the gene and inhibition of FMR1 transcription.
Full mutation: >200 CGG repeats (methylated)
Premutation: 55-200 CGG repeats (unmethylated)
Intermediate: 45-54 CGG repeats (unmethylated)
Common: 5-44 CGG repeats (unmethylated)
Clinical Sensitivity & Specificity: 99 percent for pre and full mutation alleles.
Methodology: PCR followed by capillary electrophoresis.
Analytic Sensitivity & Specificity: 99 percent.
Limitations: Rare FMR1 mutations, unrelated to trinucleotide expansion may not be detected. Precise sizing of the CGG repeats is not provided. Intermediate alleles will not be reported.



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
Note: If the screen suggests a pre or full mutation, then Fragile X (FMR1) Diagnostic will be added for analysis of sizing and methylation. Additional charges apply.
CPT Code(s): 81243
If reflexed, add 81244
Cross References: Inherited Mental Retardation (Fragile X (FMR1) Screen with Reflex to Fragile X (FMR1) Diagnostic) , Martin-Bell Syndrome (Fragile X (FMR1) Screen with Reflex to Fragile X (FMR1) Diagnostic)