DETECTING RESIDUAL BCR-ABL TRANSCRIPTS IN CHRONIC MYELOID-LEUKEMIA PATIENTS USING COUPLED REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION WITH RTTH DNA-POLYMERASE

The bcr-abl fusion gene is the hallmark of chronic myeloid leukaemia ( CML) and presumably the cause of its development. Accordingly, long-te rm disappearance of the bcr-abl gene after intensive therapy suggests that a patient is probably cured of CML. The diagnostic protocol based on coupling of two enzymatic reactions, reverse transcription (RT) an d nested polymerase chain reaction (nPCR), for the detection of bcr-ab l transcripts in peripheral blood provides a powerful tool for minimal residual CML detection. We have developed a new detection protocol us ing rTth DNA polymerase as the only enzyme catalysing both reactions f or simplifying CML diagnosis. We demonstrate its efficacy investigatin g residual leukaemic cells in the peripheral blood of 10 patients. Thi s assay offers several advantages over the use of conventional RT-PCR, being more sensitive, faster, less prone to false positives since no opening of the tube is required between the two reactions and requires no special oils or waxes. Our simple assay for bcr-abl chimeric trans cripts detection is a practical addition to the diagnostic evaluation of the patient with chronic myeloid leukaemia.