BCR-ABL1 (BCR::ABL1) Qualitative and Quantitative Testing

Last Literature Review: December 2023 Last Update:
  • Recommended initial diagnostic test for CML or ALL when the BCR::ABL1 fusion form is unknown (no previous BCR::ABL1 molecular testing performed) or unclear
  • If the qualitative test is positive for the common fusion transcripts of p210 (major breakpoint) or p190 (minor breakpoint), then the corresponding quantitative test is performed.
  • This test should not be reordered once a fusion transcript has been identified for disease monitoring; individual quantitative tests should be ordered instead.
  • Appropriate for monitoring CML or Ph+ ALL once a p210 fusion transcript has been identified
  • Quantifies the BCR::ABL1 major (p210) fusion form (e13a2 or e14a2 transcripts), which is present in almost all cases of CML and in a subset of ALL cases
  • Appropriate for monitoring Ph+ ALL or CML once a p190 fusion transcript has been identified
  • Quantifies the BCR::ABL1 p190 fusion form (e1a2 transcript)

BCR::ABL1 (BCR-ABL1) testing is recommended for patients with either chronic myeloid leukemia (CML), a hematopoietic stem cell disease, or acute lymphoblastic leukemia (ALL), an aggressive type of leukemia of either B- or T-lineage immature lymphoid cells.   These tests use reverse transcription polymerase chain reaction (RT-PCR) to identify and/or quantify the fusion transcript present.

In CML, BCR::ABL1 fusion gene identification and quantification are used for diagnosis and ongoing therapeutic monitoring.  In ALL, BCR::ABL1 fusion identification and quantification are used for risk stratification and treatment decisions.  BCR::ABL1 usion quantification is used for minimal residual disease (MRD) assessment of Philadelphia chromosome-positive (Ph+) ALL.  A qualitative test with reflex to quantitation should be performed in the diagnostic workup to identify the appropriate quantitative test for future use. Repeat qualitative testing should not be performed for therapeutic monitoring as it is less sensitive.

Refer to the following ARUP Consult topics for more disease information and summaries of the testing strategies for conditions associated with BCR::ABL1:



BCR::ABL1 (BCR-ABL1) fusion gene

Test Interpretation

BCR-ABL1, Major (p210), Quantitative

Transcripts Quantified

e13a2 or e14a2 transcripts of the BCR::ABL1 major (p210) fusion form

Analytic Sensitivity

Limit of detection: 0.0032% IS


Does not detect p190, p230, or rare variants of p210 forms

BCR-ABL1, Minor (p190), Quantitative

Transcript Quantified

e1a2 transcript of the BCR::ABL1 minor (p190) fusion form

Analytic Sensitivity

Limit of quantitation: 5 x 10-5 BCR-ABL1/ABL1 transcripts

Limit of detection: Between 10 and 20 x 10-6 BCR-ABL1/ABL1 transcripts


Does not detect p230, p210, or other rare fusion forms