Bcr-Abl, Quantitative International Scale

What is BCR-ABL1 Quantitative (IS) Test?

The BCR-ABL quantitative test measures the level of BCR-ABL1 fusion transcripts in blood or bone marrow using RT‑qPCR and reports results on the International Scale (IS) to standardize monitoring in Philadelphia chromosome–positive leukemias, especially chronic myeloid leukemia (CML).

Why consider BCR-ABL1 Quantitative (IS) Test?

• To confirm or exclude leukemias involving the BCR‑ABL1 gene (notably CML and Ph+ ALL) when clinical features or initial labs raise suspicion.
• To establish a baseline BCR‑ABL1 level at diagnosis, which is essential for tracking molecular response over time on the standardized International Scale (IS).
• To monitor response to tyrosine kinase inhibitor (TKI) therapy (e.g., imatinib, dasatinib, nilotinib) and assess depth of molecular remission; falling transcript levels indicate effective treatment.
• To detect minimal residual disease (MRD) and identify molecular relapse earlier than symptoms or routine blood counts, allowing timely treatment adjustments.
• To guide further testing (e.g., BCR‑ABL1 kinase domain mutation analysis) if transcript levels plateau or rise, suggesting resistance to current therapy.

Who should get this BCR-ABL1 Quantitative (IS) Test?

• Individuals in whom a clinician suspects CML or Ph+ ALL based on symptoms and/or abnormal blood counts (elevated white blood cells).
• Patients newly diagnosed with CML or Ph+ ALL, to obtain a baseline IS value prior to or at the start of therapy.
• Patients already on treatment for CML or Ph+ ALL, for periodic monitoring to confirm appropriate molecular response milestones and continued remission.
• Patients with previously treated disease who need surveillance to detect molecular relapse before clinical progression.
• Patients with known BCR‑ABL1–positive disease who show rising transcript levels or inadequate response, to prompt further evaluation and potential mutation testing or therapy change.

More Information BCR-ABL1 Quantitative (IS) Test

Other Names - Philadelphia chromosome Test, BCR-ABL1 Genetic Test, BCR-ABL1 Test, Philadelphia chromosome genetic test, Chronic Myeloid Leukemia Test, CML test, BCR-ABL1 RT PCR, BCR-ABL1 international test, BCR-ABL1 Quantitative IS

The BCR-ABL1 test detects the BCR-ABL1 fusion gene (Philadelphia chromosome) in blood or bone marrow, a hallmark of chronic myeloid leukemia (CML) and present in a subset of acute lymphoblastic leukemia (Ph+ ALL). It’s done by cytogenetics/FISH and by RT‑PCR to detect and quantify transcripts.