Use of test
Changes in chromosome structure and number in leukaemic cells can provide important prognostic and therapeutic information in patients with chronic lymphocytic leukaemia (CLL). A panel of probes is used to look for the most frequent abnormalities, 13q deletion, trisomy 12, ATM deletion and TP53 deletion.
The laboratory report defines the changes in the patient's malignant cells and relates these changes to the current management recommendations.
This is an assay for non-heritable mutations. It does not raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient.
Fluorescent in situ hybridisation (FISH) analysis, using probes specific to the relevant targets. This interphase FISH test has a cut off at 5%. A low level of positive cells may be due to overlap of the two signals. Studies of normal controls indicate that this level is less than 5%. Using the TP53 probe, positivity is uncertain between 5 and 10%.
Requesting the test
This test is usually requested by a haematologist or oncologist.
0.5 mL bone marrow in transport media or 10 mL blood in lithium heparin if clinically appropriate.
To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.
We recommend that the patient or another adult check the labelling of request forms and sample tubes.
5 business days.
Note that in cases of relapsed or refractory CLL, TP53 deletion testing has a Medicare rebate.
The Medicare details, including descriptor and schedule fee, are listed under MBS item 73343.