Molecular diagnostics in chronic myeloid leukemia.

With the progress of chronic myeloid leukemia (CML) therapy, the molecular tools used to diagnose and monitor patients have become sophisticated. Despite this, a complete physical examination, complete blood count and bone marrow biopsy with metaphase karyotyping remain standard at diagnosis. Fluorescence in situ hybridization or qualitative reverse transcription polymerase chain reaction are indicated to exclude BCR-ABL1 in Philadelphia chromosome-negative patients with clinically typical CML. Bone marrow karyotyping is the gold standard for monitoring patients on imatinib until achievement of complete cytogenetic response, when quantitative polymerase chain reaction (qPCR) for BCR-ABL1 becomes the method of choice. Quantitative PCR results must be interpreted within a clinical context, the preceding results and performance characteristics of the PCR assay. Expression of qPCR results on the international scale enables comparison of results from different laboratories. BCR-ABL1 kinase domain mutation screening has added another level of complexity that informs the management of some patients with imatinib resistance. Using the entire diagnostic CML armamentarium in a rational and economic fashion can be as challenging as choosing the right treatment. The aim here is to describe what is universally accepted and what is controversial and to provide an update on emerging technologies, while trying to keep an eye on the real world outside specialized centers.