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Test Code BUCCF X and Y Aneuploidy Detection, Buccal Smear, FISH

Useful For

Diagnosis of mosaic sex chromosome aneuploidy as a supplement to conventional chromosome studies in patients with normal or uncertain chromosome results or when an alternative tissue needs to be studied.

Genetics Test Information

This test is only appropriate as a supplement to conventional chromosome studies when an alternative tissue needs to be studied to detect sex chromosome aneuploidy.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
_PBCT Probe, +2 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
_IL25 Interphases, <25 No, (Bill Only) No
_I099 Interphases, 25-99 No, (Bill Only) No
_I300 Interphases, >=100 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. Additional charges will be incurred for all reflex probes performed. Analysis charges will be incurred based on the number of cells analyzed per probe set. If no cells are available for analysis, no analysis charges will be incurred.

Method Name

Fluorescence In Situ Hybridization (FISH)

Reporting Name

X,Y Aneuploidy, Buccal Smear, FISH

Specimen Type

Buccal Swab

Specimen Required

Provide a reason for referral with each specimen. The laboratory will not delay or reject testing if this information is not provided, but appropriate testing and interpretation may be compromised.


Container/Tube: Buccal Smear Collection Kit (T543)

Specimen Volume: 2 Cyto-Pak brushes

Collection Instructions:

1. Patient should rinse out mouth vigorously with mouthwash followed by water for approximately 15 seconds. Mouthwash is not a requirement but helps reduce the bacteria found in the mouth that may hinder testing.

2. Remove the Cyto-Pak brush from the container only touching the "stick" end. Save the container.

3. Using medium pressure, rotate the brush several times on the inside of the cheek.

4. Return brush to container and cap.

5. Repeat steps 2 through 4 on the other cheek using the second brush.

6. It is important that the patient's buccal cells are not contaminated with cells from any other source. Do not touch the bristles. Do not brush too vigorously. If blood appears, discard the brush and restart the collection process.

7. Label each container with patient's name and order number or hospital/clinic number.

Additional Information:

1. Provide appropriate clinical information about the patient as per specific test requirements.

2. It is important that the cells do not dry out during shipping. Ensure that the container is tightly sealed.

Specimen Minimum Volume

2 Cyto-Pak brushes

Specimen Stability Information

Specimen Type Temperature Time
Buccal Swab Ambient (preferred)

Reject Due To

Note: No specimen should be rejected. If specimen not received at appropriate temperature or in wrong anticoagulant, include note to laboratory. If questions, contact laboratory.

Clinical Information

Aneuploidy of the sex chromosomes is common among recognized congenital syndromes. For example, the majority (80%) of individuals with Klinefelter syndrome have 2 X chromosomes and 1 Y chromosome; the remainder are mosaics or variants. Individuals with Turner syndrome have a single X chromosome in 55% of cases; the remaining 45% are either variants or mosaics.


Conventional cytogenetic analysis should be performed for confirmation, especially when the results are abnormal.


Structural abnormalities of X and Y chromosomes will be missed by this technique, as will low-level mosaicism.


This test can detect between 50% to 70% of Turner syndrome cases (only those caused by complete lack of 1 sex chromosome [45,X] or high-level mosaicism for a 45,X). Congenital blood chromosome analysis (CMS / Chromosome Analysis, for Congenital Disorders, Blood) should always be performed for Turner syndrome. The test does not rule out numeric or structural cytogenetic anomalies involving chromosomes other than X and Y.

Reference Values

An interpretive report will be provided.


Specimens that contain >5% cells with a signal pattern other than XX in females and XY in males have a very high likelihood of having a clone of cells with an abnormal complement of sex chromosomes.


Specimens with <5% of cells with a signal pattern other than XX in females and XY in males most likely do not have a clone of cells with an abnormal complement of sex chromosomes, but the presence of an abnormal clone of cells is not completely ruled out.


Because this FISH test is not approved by the U.S. Food and Drug Administration, it is important to confirm any numeric X and Y chromosome abnormalities by other established methods, such as clinical history or physical evaluation.


Interfering factors:

-Excessive transport time

-Inadequate amount of specimen may not permit adequate analysis

-Improper packaging may result in broken, leaky, and contaminated specimen during transport

Method Description

Buccal mucosa cells are analyzed for XX (females) and XY (male) sex chromosome complement by using X and Y centromere probes. These probes are hybridized to interphase cells and visualized by fluorescence microscopy using FISH. Normal female cells will have 2 orange signals signifying hybridization of the X chromosome probe to both X chromosome centromeres. Normal male cells will have a single orange and a single green signal, signifying hybridization of the X chromosome probe to the X centromere and the Y chromosome probe to the Y chromosome centromere, respectively. The number of individual cells is expressed as a percentage of the total number of interphase cells analyzed. Up to 200 cells will be analyzed for the sex chromosome signal pattern.(Schad CR, Kuffel DG, Wyatt WA, et al: Application of fluorescent in situ hybridization with X and Y chromosome specific probes to buccal smear analysis. Am J Med Genet 1996;66:187-192)

Day(s) and Time(s) Performed

Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m. to 5 p.m. CST.

Analytic Time

8 days

Specimen Retention Time

Three weeks.

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. 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)     

88275 – Interphase in situ hybridization, 100 to 300 cells, each probe set (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
BUCCF X,Y Aneuploidy, Buccal Smear, FISH 87436-2


Result ID Test Result Name Result LOINC Value
51875 Result Summary 50397-9
51877 Interpretation 69965-2
54542 Result 62356-1
CG677 Reason For Referral 42349-1
51878 Specimen 31208-2
51879 Source 31208-2
51880 Method 49549-9
51876 Additional Information 48767-8
53871 Disclaimer 62364-5
51881 Released By 18771-6


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 (T576) is available in Special Instructions.