Chromosomal abnormalities resulting in deletion at 5q or monosomy 5 can occur in both acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS). Genes in the deleted region include NPM1, APC and CTNNA1. Deletions at 5q are also relatively common in therapy-related AML/MDS. These abnormalities can have diagnostic, prognostic, and therapeutic implications.
In patients with MDS, deletion of 5q (as the sole cytogenetic abnormality) is associated with a favourable prognosis. Deletion of 5q is also associated with response to lenalidomide therapy.
In patients with AML, deletion of 5q usually occurs as part of a complex karyotype, and prognosis is relatively poor.
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 within the region of 5q commonly deleted in AML/MDS. 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%. Small abnormal populations may therefore not be detectable.
Requesting the test
This test is usually requested by a haematologist or oncologist. In the investigation of myelodysplasia, it is usually requested as part of the Myelodysplastic syndrome FISH panel.
0.5 mL bone marrow in transport media (or 10 mL blood in lithium heparin if blasts >10%).
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.