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HelpTest Code FXS Fragile X Syndrome, Molecular Analysis, Varies
Useful For
Confirming a diagnosis of fragile X syndrome, fragile X tremor/ataxia syndrome, or premature ovarian insufficiency caused by expansions in the FMR1 gene
Determining carrier status for individuals with a family history of fragile X syndrome or X-linked intellectual disability
Prenatal diagnosis of fragile X syndrome when there is a documented FMR1 expansion in the family
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CULFB | Fibroblast Culture for Genetic Test | Yes | No |
| CULAF | Amniotic Fluid Culture/Genetic Test | Yes | No |
| MATCC | Maternal Cell Contamination, B | Yes | No |
| FUFXS | Fragile X, Follow up Analysis | No | No |
Testing Algorithm
When this test is ordered, fragile X follow-up analysis testing will be performed and charged dependent upon the reported sex of the individual and on the size of the CGG repeat found by polymerase chain reaction analysis.
When sending in prenatal specimens:
-If amniotic fluid (nonconfluent cultured cells) is received, amniotic fluid culture will be added at an additional charge.
-If chorionic villus specimen (nonconfluent cultured cells) is received, fibroblast culture for genetic test will be added at an additional charge.
For any prenatal specimen that is received, maternal cell contamination studies will be added.
Special Instructions
Method Name
Polymerase Chain Reaction (PCR)
Reporting Name
Fragile X Syndrome, Mol. AnalysisSpecimen Type
VariesOrdering Guidance
Due to the complexity of prenatal testing, consultation with the laboratory is required. To speak with a genetic counselor about this testing option, call 800-533-1710.
FMR1-methylation status cannot be assessed on chorionic villus specimens. Contact a molecular genetic counselor/consultant at 800-533-1710 to discuss the limitations of testing prior to sending a chorionic villus specimen for fragile X analysis.
Additional Testing Requirements
All prenatal specimens must be accompanied by a maternal blood specimen. Order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen. This must be a different order number than the prenatal specimen.
Shipping Instructions
Specimen preferred to arrive within 96 hours of collection.
Specimen Required
Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. For instructions for testing patients who have received a bone marrow transplant, call 800-533-1710.
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 whole blood specimen in original tube. Do not aliquot.
Specimen Stability Information: Ambient (preferred) 4 days/Refrigerated
Prenatal Specimens
Due to its complexity, consultation with the laboratory is required for all prenatal testing; call 800-533-1710 to speak to a genetic counselor.
Specimen Type: Amniotic fluid
Container/Tube: Amniotic fluid container
Specimen Volume: 20 mL
Specimen Stability Information: Refrigerated (preferred)/Ambient
Additional information:
1. A separate culture charge will be assessed under CULAF / Culture for Genetic Testing, Amniotic Fluid. An additional 2 to 3 weeks is required to culture amniotic fluid before genetic testing can occur.
2. All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.
Specimen Type: Chorionic villi
Container/Tube: 15-mL tube containing 15 mL of transport media
Specimen Volume: 20 mg
Specimen Stability Information: Refrigerated
Additional Information:
1. A separate culture charge will be assessed under CULFB / Fibroblast Culture for Biochemical or Molecular Testing. An additional 2 to 3 weeks is required to culture chorionic villi before genetic testing can occur.
2. All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.
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
Additional Information: All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.
Specimen Minimum Volume
Blood: 0.5 mL
Amniotic fluid: 10 mL
Chorionic villi: 5 mg
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Varies | ||
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Reference Values
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.
Methylation status:
Unmethylated: ≤20%
Partially methylated: 21-69%
Fully methylated: ≥70%
Day(s) Performed
Monday, Wednesday
Report Available
8 to 10 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
81243
88233 (if appropriate)
88240 (if appropriate)
88235 (if appropriate)
81265 (if appropriate)
81244 (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| FXS | Fragile X Syndrome, Mol. Analysis | 81856-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 52870 | Result Summary | 50397-9 |
| 52871 | Result | 81856-7 |
| 52872 | Interpretation | 69047-9 |
| 52873 | Reason for Referral | 42349-1 |
| 52874 | Specimen | 31208-2 |
| 52875 | Source | 31208-2 |
| 52876 | Method | 85069-3 |
| 52877 | Released By | 18771-6 |
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.Forms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Molecular Genetics: Congenital Inherited Diseases Patient Information (T521)
3. If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.