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Molecular Analysis:
Bcr/Abl Gene Rearrangement (t 9;22), Qualitative RT-PCR Assay
The 9;22 Philadelphia chromosome translocation is found in approximately 95% of patients with chronic myelogenous leukemia (CML), 10-25% of adult patients with acute lymphocytic leukemia (ALL), 5% of children with ALL, and occasionally in patients with acute myelogenous leukemia (AML). This translocation is the result of the transposition of the Abl proto-oncogene from chromosome 9 to the Bcr (breakpoint cluster region) gene on chromosome 22. The Bcr/Abl fusion gene forms one to three distinct chimeric mRNAs, depending on the specific breakpoint in the Bcr gene. The fusion mRNA in CML patients results from breakpoints in M-Bcr (major breakpoint cluster region) exon 2 or 3 and fusion to Abl exon II (b2a2, b3a2). The fusion mRNA in the majority of ALL patients results from a breakpoint in m-Bcr (minor breakpoint cluster region) exon 1 and fusion to Abl exon II (e1a2). Some ALL patients have breakpoints in M-Bcr which are identical to those breakpoints found in CML patients.
- Confirm the presence of Bcr/Abl fusion transcripts in patients with CML or ALL
- Confirm the presence of Bcr/Abl fusion transcripts when the Ph chromosome is not detected by cytogenetics
Our testing methodology involves reverse transcriptase polymerase chain reaction (RT-PCR) followed by nested primer PCR analysis and gel electrophoresis to detect the Bcr/Abl fusions arising from breakpoints in exon 2 and exon 3 of M-Bcr. This assay will not detect the Bcr/Abl fusion arising from the breakpoint in exon 1 of m-Bcr, which is more common in ALL.
In our laboratory, the analytic sensitivity of this qualitative assay is 1 in 100000. Multiple RT-PCR reactions may yield equivocal results.
The results from this assay should always be interpreted in the context of morphologic and other relevant data. The results should not be used alone for a diagnosis of malignancy.
Blood: 5 cc collected in a purple top (EDTA) or yellow top (acid citrate dextrose) vacutainer tube. Do not centrifuge or freeze. Specimen should be stored in the refrigerator and transported with a cold pack or on wet ice. Specimen should reach the laboratory within 48 hours of collection.
Bone marrow: 1 - 2 cc collected in a purple top (EDTA) or yellow top (acid citrate dextrose) vacutainer tube. Do not centrifuge or freeze. Specimen should be stored in the refrigerator and transported with a cold pack or on wet ice. Specimen should reach the laboratory within 48 hours of collection.
7 - 10 days
83891, 83894, 83900, 83901 (2X), 83902, 83912
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