BCR-ABL Gene Rearrangement

Function

The BCR-ABL test detects a specific genetic abnormality known as the Philadelphia chromosome. This occurs when pieces of chromosome 9 and chromosome 22 break off and switch places, creating a fusion gene (BCR-ABL1). This fusion gene produces an abnormal protein (tyrosine kinase) that causes white blood cells to grow uncontrollably.

Why it is Ordered

This test is primary used for:

• Diagnosis: To confirm a diagnosis of Chronic Myeloid Leukemia (CML) or a specific type of Acute Lymphoblastic Leukemia (ALL).
• Monitoring: To evaluate the effectiveness of treatment with Tyrosine Kinase Inhibitors (TKIs) like imatinib.
• Detection of Relapse: To check if the disease is returning after a period of remission.

Associated Conditions

• Chronic Myeloid Leukemia (CML): Almost all patients with CML have the BCR-ABL gene.
• Acute Lymphoblastic Leukemia (ALL): About 25-30% of adults and a smaller percentage of children with ALL have this mutation.
• Acute Myeloid Leukemia (AML): Rarely, this mutation can be found in AML cases.

Clinical Utility

The quantitative version of this test (RT-qPCR) is extremely sensitive, capable of detecting one leukemic cell among 100,000 to 1,000,000 normal cells. This allows clinicians to achieve 'Major Molecular Response' (MMR) monitoring, which is the gold standard for long-term survival in CML patients.