Test Background The BCR-ABL1 fusion gene is formed by a reciprocal translocation between chromosomes 9 and 22 [t(9;22)]. This reciprocal translocation creates an elongated chromosome 9 and a short chromosome 22 (the Philadelphia chromosome). There is a BCR-ABL gene fusion on the short chromosome 22 which is present in virtually all individuals with CML and, as such, is considered the hallmark diagnostic feature of the disease. However, this is not exclusive to CML and can also be a feature in some cases of ALL.
BCR-ABL1 gene transcripts are detected and measured using PCR. This technique is also used to test for mutations of the ABL1 tyrosine kinase domain, which can denote a molecular cause for resistance to BCR-ABL1 tyrosine kinase inhibitor (TKI) treatment. If a mutation is detected this will guide clinicians to a more appropriate course of treatment.
Clinical Indications Molecular levels of BCR-ABL1 can be monitored during the course of TKI treatment (imatinib, dasatinib, nilotinib, bosutinib and ponatinib), which is a first line treatment for CML. Monitoring can also apply to patients prior to and post transplantation.
Sample Required Blood or bone marrow in EDTA (lavender top)
Sample Volume 20 mL blood or 2.5-5.0 mL bone marrow within 72 hours of collection
Turnaround Time BCR-ABL1 – 10 working days
Mutation analysis of the ABL1 tyrosine kinase domain – 20 working days