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BCR-ABL, NON-BLOOD

Test Code: BMBCRQ
Description: Translocation of the ABL1 gene on chromosome 9 to the BCR gene on chromosome 22 creates a chimeric BCR-ABL1 gene [the Philadelphia chromosome or t(9;22)]. This transcriptionally active gene encodes a fusion protein, which is leukemogenic.

The Stanford Molecular Pathology Laboratory will perform Qualitative and/or Quantitative testing depending on whether the sample was tested in this laboratory previously and based on prior results obtained by this laboratory.

Qualitative BCR-ABL1 testing is performed by PCR amplification of reverse-transcribed RNA using primers specific to the Major breakpoint regions e13a2 and e14a2 (also known as b2a2 and b3a2, respectively) common in CML and minor breakpoint region (e1a2) common in ALL. The sensitivity of the qualitative assay is 0.01% BCR-ABL1 detection in a background of normal RNA.

Quantitative BCR-ABL1 testing is performed by a real-time RT-PCR using primers specific to the Major e13a2 and e14a2 (also known as b2a2 and b3a2, respectively) and minor (e1a2) breakpoint regions. A control gene (ABL1) is amplified as an internal standard. Each sample is amplified in duplicate for both the target (BCR-ABL1) and control (ABL1). Quantification is determined from known calibration standards. The quantitative assay has a sensitivity of 0.001% BCR-ABL1 detection in a background of normal RNA. The Stanford Molecular Laboratory p210 (representing e13a2 and e14a2 fusions) diagnostic average for new diagnosis is 0.5687 p210 copies/ABL1copies.

The International Scale (IS) was established in 2005 to standardize quantitative BCR-ABL1 measurements across tests and laboratories (Hughes et al., Blood 2006). The IS is anchored to the baseline BCR-ABL1 expression level from the International Randomized Study of Interferon vs STI571 (IRIS) trial (100% IS) with a major molecular response (MMR) corresponding to 0.1% IS (Hughes et al., N Engl J Med 2003). The IRIS trial and follow up studies have demonstrated that achieving MMR, or a 3-log reduction in BCR-ABL1 expression from the standardized baseline level, is a key clinical outcome.

Percent ratios on the IS are obtained by multiplying the percent ratio (100 x BCR-ABL1 / ABL1) by the Qiagen (Ipsogen) test-specific conversion factor (IS % ratio = local % ratio x conversion factor).


 
 


 
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