Reference Interval:
| Test Number
| Components
| Reference Interval
| | | Fragile X (FMR1) Mutation Screen
| By report
| | 0040011 | Fragile 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.
Refer to Statement C under Testing Information at http://www.aruplab.com.
|
| 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): |
83891 Isolation; 83898 Amplification; 83909 Capillary electrophoresis; 83912 Interpretation & report; if reflexed, add PCR: 83891 Isolation; 83898 x2 Amplification; 83909 Capillary electrophoresis. Southern Blot: 83891 Isolation; 83892 x2 Digestion; 83894 Gel Separation; 83897 Southern transfer; 83896 Nucleic acid probe; 83912 Interpretation & report - Additional CPT code modifiers may be required for procedures performed to test for oncologic or inherited disorders.
|
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)
|