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Mayo Test ID XYMF Known 45,X, Mosaicism Reflex Analysis, FISH, Whole Blood


Ordering 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.


Useful For

Detecting sex chromosome mosaicism in patients with a 45,X karyotype

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

This test includes a charge for application of the first probe set (2 FISH probes) and professional interpretation of results.

 

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, FISH

Specimen Type

Whole blood

Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
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 days

Specimen Retention Time

4 weeks

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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.

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)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
XYMF Known 45,X Mosaicism Reflex, FISH 87436-2

 

Result ID Test Result Name Result LOINC Value
51844 Result Summary 50397-9
51846 Interpretation 69965-2
54537 Result 62356-1
CG668 Reason for Referral 42349-1
51847 Specimen 31208-2
51848 Source 31208-2
51849 Method 85069-3
54451 Additional Information 48767-8
55279 Disclaimer 62364-5
51850 Released By 18771-6