To describe the approach used by an individual laboratory for development and validation of a laboratory-developed quantitative reverse transcription polymerase chain reaction test for BCR-ABL1 fusion transcripts.     ///    Elements of design and analytic validation of a laboratory-developed quantitative molecular test are discussed using quantitative detection of BCR-ABL1 fusion transcripts as an example.     ///    Design and analytic validation of BCR-ABL1 quantitative reverse transcription polymerase chain reaction assay for monitoring minimal residual disease..     ///    We demonstrate how one laboratory validated and clinically implemented a quantitative BCR-ABL1 assay that can be used for the management of patients with chronic myelogenous leukemia.. 