Search our Test Catalog. Specify what to search (name, test code, titles, everywhere) and how to search (begins with, contains)

Unit Code 80601:
XX/XY in Opposite Sex Bone Marrow Transplantation, FISH

Print Friendly View
Print Page Email Page

Useful For

Evaluating engraftment success by determining the proportion of

donor and recipient interphase cells present in opposite sex bone

marrow transplant recipients

 

Monitoring the proportion of host and recipient cells over time may

be useful to identify significant clinical changes

Clinical Information

Bone marrow transplantation (BMT) is an important treatment for

patients with certain malignant hematologic disorders and hereditary

conditions.

 

Conventional cytogenetic studies can identify chromosome

abnormalities, establish the proportion of donor and recipient

metaphase cells to monitor the success of BMT engraftment, and

detect residual disease after treatment. However, conventional

chromosome studies are usually done on only 20-30 metaphase

cells and may be less sensitive than other methods.

 

When the donor and recipient are of opposite sex, the donor and

recipient cells can be readily identified by their sex chromosome

complement. Fluorescence in situ hybridization (FISH) using probes

for the X and Y chromosomes can be used to estimate the proportion

of donor and recipient interphase cells in bone marrow or peripheral

blood. Monitoring the proportion of host and recipient cells over time

also may be useful to identify significant clinical changes.

 

This method is easy, objective, and permits analysis of large numbers

of cells. Our experience also suggests that FISH is economical, rapid,

and accurate.(1) FISH specimens are preprocessed in the same

manner as chromosome analysis specimens. If FISH results or

clinical circumstances suggest the possibility of disease relapse,

chromosome studies can be performed on the same specimen to

determine if an abnormal clone is present.

 

To maximize the cost-effectiveness of FISH and chromosome

analysis, we recommend conventional chromosome analysis prior

to BMT to establish the karyotype of the malignant cell line. After

BMT, the use of FISH alone on either bone marrow or peripheral

blood may be sufficient to monitor the success of the engraftment.

Reference Values

< or = 0.3% cells with XY signals for pretransplant females

< or = 0.6% cells with XX signals for pretransplant males

Interpretation

Specimens from females that have >0.6% XX interphase cells have

residual XX host cells.

 

Specimens from males that have >0.3% XY interphase cells have

residual XY host cells.

 

The results of both conventional chromosome studies and FISH are

best interpreted when findings before and after BMT are compared. 

Our reports include a summary of the percentage of host and donor

cells present in prior studies from the same patient.

Cautions

This test is designed for opposite sex bone marrow transplants only;

results are not useful for same sex bone marrow transplants.  

 

Examination of the sex chromosome complement of interphase cells

using FISH does not distinguish between malignant and normal cells.

We strongly recommend using both FISH and cytogenetic studies to

monitor patients.

 

A single X chromosome is sometimes lost in bone marrow cells of

females, and the Y chromosome is sometimes lost in bone marrow

cells of males, regardless of whether the specimen is from the donor,

recipient, or a post-BMT patient.

 

Rare males may have an unusual Y chromosome that cannot be

identified with these probes, but this finding should be readily apparent

by analysis of metaphase cells using FISH.

 

Occasional patients may have chromosome polymorphisms that may

hybridize with the Y probe, but this should be readily apparent by

analysis of metaphase cells using FISH.

 

#9495 "Chimerism Analysis,” also is available for patients of

opposite-sex transplantation as well as same-sex transplantation.  

The chimerism analysis may be more sensitive for detecting very

low levels of donor or recipient cells. This analysis requires multiple

specimens. Please see #9495 "Chimerism Analysis” to obtain more

information.

Special Instructions and Forms

• MayoConnect Additional Test Information 

Clinical Reference

Dewald GW, Schad CR, Christensen ER, et al:  Fluorescence in situ

hybridization with X and Y chromosome probes for cytogenetic studies

on bone marrow cells after opposite sex transplantation. Bone

Marrow Transplant 1993;12:149-154

Key