Reference genes

A reference gene is a gene that is transcribed to a constant level in all cells at the same time, providing a reference point for the measurement of fluorescence intensity and allowing comparison between tests done at different times during monitoring of a patient. An ideal reference gene is expressed consistently between different cell types and patients, and over the course of treatment. It should also be expressed at a level similar to that of BCR–ABL1 and be broken down at a similar rate, since delays between blood sampling and testing can differentially alter levels of different mRNAs. ABL1 is an ideal reference gene, so BCR–ABL1 transcript burden is normally reported as the BCR–ABL1:ABL1 ratio; some laboratories use β-glucuronidase as a reference gene instead.