The t(9;22) chromosomal translocation is a hallmark of chronic myelogenous leukemia (CML) and occurs in a proportion of acute lymphocytic leukemias (ALL). At the molecular level, it creates a chimeric gene on the derivative chromosome 22 that is comprised of the promoter and 5’ region of the BCR gene (22q11) fused to the 3’ region of the ABL1 gene (9q34). Transcription of this fusion gene, which is under the control of the ubiquitously active BCR promoter, results in a BCR/ABL1 chimeric oncoprotein that is critical for malignant transformation. Depending upon the location of the BCR and ABL1 gene breakpoints, the resulting chimeric fusion transcript can assume one of several forms, including the b2a2 and b3a2 forms, which both encode a p210 protein (>95% of CML cases, approximately 50% of adult ALL cases, approximately 10% of pediatric ALL cases), the e1a2 form, which encodes the p190 protein (2-3% of CML cases, 50% of ALL cases, approximately 90% of pediatric ALL cases), or an e19a2 form which encodes the p230 protein form (very rare). This test can detect and quantify both the p210 (b2a2, b3a2) and p190 (e1a2) transcripts by reverse transcription real-time PCR (RT-qPCR) for diagnosis and monitoring of CML and ALL. The type of transcript will be reported (p210 or p190). Results for the p210 transcript are reported on the International Scale (IS) and with Molecular Reduction (MR) value. Result for the p190 transcript are reported as a ratio of %BCR/ABL1:ABL1. The limit of quantification for p210 is 0.002%IS (MR4.7) and p190 is 0.0025%. Please note that both tests (p210 and p190) will be performed until a transcript is detected. Subsequent testing on the same patient will be limited to the transcript previously identified.