BCR-ABL

Molecular Haematology

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Description

The presence of a novel, minute chromosome in the cells of patients with chronic myeloid leukaemia (CML) was first described in 1960, and became known as the Philadelphia (Ph) chromosome. It results from the reciprocal translocation between the long arms of chromosomes 9 and 22 t(9;22)(q34:q11). Molecular studies demonstrated that the translocation disrupted the normal ABL and BCR genes on chromosomes 9 and 22 respectively, giving rise to a chimeric BCR-ABL gene encoding a fusion protein.The standard Ph chromosome is found in 90% of cases of CML and cytogenetic variants account for a further 5%. Of the remaining 5% roughly half show a BCR-ABL fusion mRNA by PCR. The Ph chromosome is also the single most common chromosomal abnormality in acute lymphoblastic leukaemia. About 1% of AML cases are also Ph positive.The polymerase chain reaction (PCR) is a rapid and powerful method for detection of BCR-ABL cDNA after reverse transcription of mRNA. PCR efficiently detects BCR-ABL in BCR rearranged Ph negative patients and may also be used to detect minimal residual disease.

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Indications

Used at diagnosis in cases of suspected CML, ALL (to see if Ph+) and for subsequent disease monitoring.

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Sample Type

5ml EDTA blood or bone marrow, less than 48 hrs old.

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Turnaround Time

Within 4 weeks

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Testing Frequency

As required.

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External Notes

Level of detection 1 leukaemic cell in 105 normal cells

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.