Test ID: FXPB
Fragile X Syndrome, Molecular Analysis
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Determination of carrier status for individuals with a family history of fragile X syndrome or X-linked mental retardation
Confirmation of a diagnosis of fragile X syndrome, fragile X tremor/ataxia syndrome, or premature ovarian failure caused by expansions in the FMR1 gene
Prenatal diagnosis of fragile X syndrome when there is a documented FMR1 expansion in the family
Reflex Tests Lists test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| FBC | Fibroblast Culture for Genetic Test | Yes | No |
| AFC | Amniotic Fluid Culture/Genetic Test | Yes | No |
| FXFU | Fragile X, Follow Up Analysis | No | No |
| MCC | Maternal Cell Contamination, B | Yes | No |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
When this test is ordered, fragile X follow-up analysis testing will be performed and charged dependent upon on the size of the CAG repeat found by PCR analysis.
For prenatal specimens only: If amniotic fluid (non-confluent cultured cells) is received, amniotic fluid culture/genetic test will be added and charged separately. If chorionic villus specimen (non-confluent cultured cells) is received, fibroblast culture for genetic test will be added and charged separately. For any prenatal specimen that is received, maternal cell contamination studies will be added.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Polymerase Chain Reaction (PCR)-Based Assays
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Fragile X tremor ataxia syndrome
FXTAS
Martin-Bell Syndrome
POF
Premature ovarian failure
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Forms:
1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
2. Molecular Genetics-Congenital Inherited Diseases Patient Information Sheet (Supply T521) in Special Instructions
3. If not ordering electronically, submit a Molecular Genetics Request Form (Supply T245) with the specimen.
Specimen must arrive within 96 hours of collection.
Submit only 1 of the following specimens:
Specimen Type: Whole blood
Container/Tube:
Preferred: Lavender top (EDTA) or yellow top (ACD)
Acceptable: Any anticoagulant
Specimen Volume: 3 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send specimen in original tube.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Due to the complexity of prenatal testing, consultation with the laboratory is required for all prenatal testing. Prenatal specimens can be sent Monday through Thursday and must be received by 5 p.m. CST on Friday in order to be processed appropriately. All prenatal specimens must be accompanied by a maternal blood specimen. Order MCC/88636 Maternal Cell Contamination, Molecular Analysis on the maternal specimen.
Specimen Type: Amniotic fluid
Container/Tube: Amniotic fluid container
Specimen Volume: 20 mL
Specimen Stability Information: Refrigerated (preferred)/Ambient
Specimen Type: Chorionic villi
Container/Tube: 15-mL tube containing 15 mL of transport media
Specimen Volume: 20 mg
Additional Information: FMR1-methylation status cannot be assessed on some chorionic villus specimens. Contact a genetic counselor/consultant at Mayo Medical Laboratories at 800-533-1710 or 507-266-5700 to discuss the limitations of testing prior to sending a chorionic villus specimen for fragile X analysis.
Specimen Stability Information: Refrigerated
Acceptable:
Specimen Type: Confluent cultured cells
Container/Tube: T-25 flask
Specimen Volume: 2 flasks
Collection Instructions: Submit confluent cultured cells from another laboratory.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Amniotic Fluid: 10 mL/Chorionic Villi: 5 mg
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Varies | |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Fragile X syndrome is an X-linked disorder with variable expression in males and females. It is caused by an expansion of the CGG trinucleotide repeat in the FMR1 gene, located on the X chromosome. This trinucleotide repeat is polymorphic in the general population, with the number of repeats ranging from 5 to 44. These normal alleles are passed from generation to generation with the number of repeats remaining constant. Small expansions, called premutations, most often range from 59 to 200 CGG repeats. Premutation carriers do not exhibit features of fragile X syndrome, but are at risk for other FMR1-related disorders such as fragile X tremor/ataxia syndrome (FXTAS) and premature ovarian failure (POF). Transmission of a premutation by a male to his daughter usually results in little or no change in the CGG repeat number. Transmission of a premutation by a female to her son or daughter usually results in further expansion, either to a larger premutation or a full mutation. The risk for a female premutation carrier to have a child affected with fragile X syndrome by expansion to a full mutation increases with the number of CGG repeats in the premutation. Full mutations can be 200 to thousands of repeats long, and are associated with abnormal methylation of a region adjacent to the FMR1 gene. This is thought to interfere with normal FMR1 gene expression, resulting in fragile X syndrome. There are multiple clinical phenotypes associated with expansion (premutations and full mutations) in the FMR1 gene.
Fragile X syndrome
Approximately 1/4000 individuals (male and female) are affected with fragile X syndrome. Most affected males exhibit moderate mental retardation, with affected females having milder (if any) cognitive deficiency. Neuropsychiatric diagnoses such as autism spectrum and anxiety disorders are common. Characteristic physical features include a long face with prominent jaw, protruding ears, connective tissue abnormalities, and large testicles in postpubertal males.
Fragile X tremor/ataxia syndrome (FXTAS)
FXTAS is a neurodegenerative disorder that is clinically distinct from fragile X syndrome. Both male and female premutation carriers are at risk for FXTAS. However, the disorder is much less common, milder in presentation, and shows a later age of onset in females. Clinical hallmarks of the disorder include intention tremor, gait ataxia, dementia, and neuropsychiatric symptoms. The risk for FXTAS increases as the number of CGG repeats increases, and the majority of individuals with FXTAS have CGG repeat expansions of 70 or more. Penetrance of clinical symptoms is associated with increasing age, with the majority of affected males showing symptoms between age 70 and 90.
Premature ovarian failure (POF)
Female premutation carriers are at risk for increased follicular stimulating hormone (FSH) levels, early menopause, and POF. Penetrance and early onset of female reproductive symptoms correlates with increasing size of the CGG repeat, and reaches its highest penetrance at approximately 80 to 90 repeats. Of note, penetrance actually remains stable or may even decrease at approximately 100 repeats. There is no risk for increased penetrance of the POF phenotype due to maternal or paternal inheritance of the expanded CGG repeat.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Normal alleles: 5-44 CGG repeats
Intermediate (grey zone) alleles: 45-54 CGG repeats
Premutation alleles: 55-200 CGG repeats
Full mutation alleles: >200 CGG repeats
An interpretive report will be provided.
Interpretation Provides information to assist in interpretation of the test results
An interpretive report will be provided.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
For predictive testing, it is important to first document the presence of a CGG-repeat amplification in the FMR1 gene in an affected family member to confirm that molecular expansion is the underlying mechanism of disease in the family.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.
Methylation status cannot be assessed on chorionic villus specimens.
A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.
Less than 1% of individuals clinically diagnosed with fragile X syndrome do not have the CGG amplification-type mutation. These individuals may have a different type of mutation within the FMR1 gene (eg, deletion or point mutation) or a mutation in another gene.
Due to incomplete penetrance and variable expression of the FMR1 expansion, this test is not reliable for prenatal assessment of disease severity.
The absence of an expansion in the FMR1 gene does not eliminate the diagnosis of other inherited disorders that have overlapping clinical features with fragile X syndrome, fragile X tremor/ataxia syndrome, or premature ovarian failure.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Jacquemont S, Hagerman RJ, Hagerman PJ, Leehey MA: Fragile-X syndrome and fragile X-associated tremor/ataxia syndrome: two faces of FMR1. Lancet Neurol 2007;6(1):45-55
2. Mc-Conkie-Rosell A, Finucane B, Cronister A, et al: Genetic counseling for fragile X Syndrome: updated recommendations of the National Society of Genetic Counselors. J Genet Couns 2005;14(4):249-270
3. Sherman S, Pletcher BA, Driscoll DA: Fragile X syndrome: diagnostic and carrier testing (ACMG Practice Guideline). Genet Med 2005;7:584-587
Method Description Describes how the test is performed and provides a method-specific reference
The (CGG)(n)-repeat number for normal, intermediate, and premutation alleles is determined by analyzing a PCR-amplified product by capillary electrophoresis (Celera). Additionally, confirmation of premutation and full mutation alleles and determination of methylation status are assessed by Southern blot analysis of PCR-amplified product from DNA that is treated with a methylation-sensitive restriction enzyme.(Wilson J, Pratt V, Phansalkar A, et al: Consensus Characterization of 16 FMR1 Reference Materials: A Consortium Study. J Mol Diagn 2008;10:2-12; Snow K, Doud L, Hagerman R, et al: Analysis of a CGG sequence at the FMR-1 locus in fragile X families and in the general population. Am J Hum Genet 1993;53:1217-1228)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday, Wednesday; 10 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
81243-FMR1 (fragile 1 mental retardation 1) (eg, fragile X mental retardation) gene analysis; evaluation to detect abnormal (eg, expanded) alleles
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 16468 | Specimen | 31208-2 |
| 16469 | Specimen ID | N/A |
| 16470 | Source | N/A |
| 16471 | Order Date | N/A |
| 16472 | Reason For Referral | 42349-1 |
| 16473 | Method | In Process |
| 16474 | Result | 36913-2 |
| 16475 | Interpretation | 69047-9 |
| 16476 | Amendment | In Process |
| 16477 | Reviewed By: | N/A |
| 16478 | Release Date | N/A |
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