[The genetic diagnosis of hematopoietic malignancy by polymerase chain reaction method]

Since 1994, chimeric gene test for major-BCR/ABL, minor-BCR/ABL, AML1/MTG8, PML/RARa, DEK/CAN, CBFb/MYH11, MLL/LTG9, E2A/PBX1, TEL/AML1, and MLL/LTG4 by reverse transcription-nested-polymerase chain reaction (RT-nested-PCR) have been routinely performed in our laboratory. The frequently requested tests were those for major-BCR/ABL, minor-BCR/ABL, AML1/MTG8, PML1/RARa, and TEL/AML1 chimeric genes, being the test for major-BCR/ABL the most frequent one, accounting for more than 50% of the total orders. By the high sensitivity for minimal residual disease(MRD) detection, these methods are extremely useful for the therapeutic control of chemotherapy and bone marrow transplantation, as well as for prediction of prognosis. However, in the most cases a well-controlled monitoring could not be obtained, due to the 6-months interval between the tests, the minimal interval allowed by the insurance. The following points should be carefully observed. (1) The setting site of the primer can affect the sensitivity and the specificity of the test; (2) For the detection of chimeric genes with multiple translocation breakpoints, a genetic DNA sequencing is necessary to confirm them; (3) In patients receiving chemotherapy or bone marrow transplantation, that show extremely low blood cell counts, false-negative tests dependent on the quality of the extracted RNA and the low volume of DNA, should be avoided by careful managements. For improvements of the MRD detection tests, the quantification of the expression levels of chimeric gene and WT1 mRNA is necessary.