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HelpTest ID XYMF Known 45,X, Mosaicism Reflex Analysis, FISH, Whole Blood
Useful For
Detecting sex chromosome mosaicism in patients with a 45,X karyotype
Genetics Test Information
This test is only appropriate to detect low levels of sex chromosome mosaicism when a nonmosaic 45,X karyotype has been observed.
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| _I099 | Interphases, 25-99 | No, (Bill Only) | No |
| _I300 | Interphases, >=100 | No, (Bill Only) | No |
| _IL25 | Interphases, <25 | No, (Bill Only) | No |
| _PADD | Probe, +1 | No, (Bill Only) | No |
| _PB02 | Probe, +2 | No, (Bill Only) | No |
| _PB03 | Probe, +3 | No, (Bill Only) | No |
| _PBCT | Probe, +2 | No, (Bill Only) | No |
Testing Algorithm
Appropriate ancillary probes may be performed at consultant discretion to render comprehensive assessment. Any additional probes will have the results included within the final report and will be performed at an additional charge.
Method Name
Fluorescence In Situ Hybridization (FISH)
Reporting Name
Known 45,X Mosaicism Reflex, FISHSpecimen Type
Whole bloodOrdering Guidance
This test does not detect other chromosomal or structural anomalies and is intended to be ordered after a complete chromosome analysis.
Shipping Instructions
Advise Express Mail or equivalent if not on courier service.
Necessary Information
A reason for testing must be provided. The laboratory will not reject testing if this information is not provided however an applicable indication for testing may be entered by Mayo Clinic Laboratories. Appropriate testing and interpretation may be compromised or delayed.
Specimen Required
Container/Tube:
Preferred: Green top (sodium heparin)
Acceptable: Lavender top (EDTA) or yellow top (ACD)
Specimen Volume: 4 mL
Collection Instructions
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
3. Other anticoagulants are not recommended and are harmful to the viability of the cells.
4. Cord blood is acceptable
Additional Information:
1. If the specimen does not grow in culture, you will be notified within 7 days of receipt.
2. Specimen cannot be frozen.
Specimen Minimum Volume
2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Whole blood | Ambient (preferred) | |
| Refrigerated | ||
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
This test is appropriate for use in individuals with a karyotype of 45, X.
Ullrich-Turner syndrome (UTS), also called Turner syndrome, is a genetic disorder associated with the apparent loss of a sex chromosome. Routine cytogenetic methods have identified 3 types of chromosomal abnormalities in UTS patients: loss of an entire X chromosome (45,X), structural X chromosome abnormalities, and mosaicism with an X or Y abnormality. In mosaicism, 2 or more populations of cells with different karyotypes are present (eg, 45,X/47,XXX).
The incidence of UTS is approximately 1 in 3000 phenotypic female newborns. Many of these patients demonstrate the 45,X karyotype. About 30% to 50% are mosaic, with either a 45,X/46,XX karyotype or a structurally abnormal X chromosome. Fewer than 15% of patients with UTS appear to have mosaicism with a 46,XY cell population or a Y chromosome rearrangement.
Identifying the mosaic status of patients with UTS is of clinical importance because phenotypic expression and clinical management are dependent upon the karyotype result. Patients with a Y chromosome have a 15% to 25% increased risk of gonadoblastoma.
Failure to identify an XY signal pattern does not rule out the possibility of less than 0.6% Y chromosome mosaicism.
Reference Values
An interpretive report will be provided.
Interpretation
An XX clone is confirmed when at least 1.0% of cells display with 2 X chromosome signals. An XY clone is confirmed when at least 0.6% of cells display a 1 X and 1 Y signal pattern.
Phenotypic females with a 45,X/46,XX karyotype have no increased risk of gonadoblastoma and generally have a more moderate expression of Turner syndrome features than phenotypic females with a nonmosaic 45,X karyotype. The presence of a Y chromosome confers increased risk of gonadoblastoma.
Cautions
This test is not approved by the US Food and Drug Administration, and it is best used as an adjunct with other established methods to confirm an X or Y chromosome mosaicism diagnoses, such as existing clinical history or physical evaluation.
Interfering factors
-Cell lysis caused by forcing the blood quickly through the needle
-Use of an improper anticoagulant (sodium heparin is best) or improperly mixing the blood with the anticoagulant
-Excessive transport time
-Inadequate amount of specimen may not permit adequate analysis
-Improper packaging may result in broken, leaky, and contaminated specimen during transport.
-Exposure of the specimen to temperature extremes (either freezing or >30° C) may kill cells and interfere with attempts to culture cells
-In prenatal specimens, a bloody specimen may interfere with attempts to culture cells and contamination by maternal cells may cause interpretive problems
Clinical Reference
1. Canto P, Kofman-Alfaro S, Jiminez AL, et al. Gonadoblastoma in Turner syndrome patients with nonmosaic 45,X karyotype and Y chromosome sequences. Cancer Genet Cytogenet. 2004;150(1):70-72
2. Wiktor A, Van Dyke DL. FISH analysis helps identify low-level mosaicism in Ullrich-Turner syndrome patients. Genet Med. 2004;6(3):132-135
3. Sybert VP, McCauley E. Turner syndrome. N Engl J Med. 2004;351:1227-1238
4. Gravholt CH, Andersen NH, Conway GS, et al. Clinical practice guidelines for the care of girls and women with Turner syndrome: proceedings from the 2016 Cincinnati International Turner Syndrome Meeting. Eur J Endocrinol. 2017;177(3):G1-G70
Method Description
This test is performed using a commercially available enumeration strategy probe set for the centromere regions of the X (DXZ1) and Y (DYZ3) chromosomes. The probe set is hybridized to the appropriate target areas, and 2 technologists independently analyze 250 interphase nuclei (500 total) to determine the sex chromosome complement.(Wiktor A, Van Dyke DL. FISH analysis helps identify low level mosaicism in Ullrich-Turner syndrome patients. Genet Med. 2004;6(3):132-135)
Day(s) Performed
Monday through Friday
Report Available
7 to 9 daysTest 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.CPT Code Information
88271x2, 88291-DNA probe, each (first probe set), Interpretation and report
88271x2-DNA probe, each; each additional probe set (if appropriate)
88271x1-DNA probe, each; coverage for sets containing 3 probes (if appropriate)
88271x2-DNA probe, each; coverage for sets containing 4 probes (if appropriate)
88271x3-DNA probe, each; coverage for sets containing 5 probes (if appropriate)
88274 w/modifier 52-Interphase in situ hybridization, <25 cells, each probe set (if appropriate)
88274-Interphase in situ hybridization, 25 to 99 cells, each probe set (if appropriate)
NY State Approved
YesForms
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: