Undetected BCR/ABL but low levels of ABL detected

Low levels of ABL detected refers to the detection of the ABL gene, which is a normal gene present in all cells. The ABL gene serves as a control in PCR tests to confirm the test's accuracy. Low levels of ABL are expected and do not indicate the presence of cancer. BCR-ABL is the mutation (caused by translocation) which causes CML disease between the bcr gene on one chromosome 22 fusing with the abl gene on chromosome 9 during cell division. In PCR testing, the abl gene is the reference gene. It is always present and is part of the background data. Many PCR tests do not even report it as it is not a disease indicator.

*(the resulting bcr-abl oncogene following translocation ends up on chromosome 22. This "new" mutant chromosome is what is termed the "Philadelphia Chromosome" first described in 1960 by Peter Nowell from University of Pennsylvania School of Medicine and David Hungerford from the Fox Chase Institute for Cancer Research and named after Philadelphia, the city where University of Pa. is located.)