OBJECTIVETo investigate the relationship between three types of bcr/abl fusion transcripts and clinical manifestation in chronic myeloid leukemia (CML).

METHODM-, m- and micro -bcr/abl fusion transcripts were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) technique in 537 fresh bone marrow samples of patients suspected CML clinically.

RESULTSOf 573 patients, 479 expressed M-bcr/abl transcripts, among whom 370 were in chronic phase (CP), and 109 in accelerated (AP)/blastic phase (BP). The percentages of patients with b2a2 transcripts in CP and AP/BP were 32.4% (120/370) and 36.7% (40/109) (P > 0.05). The b2a2 transcript patients in blastic crisis were 52.6% (10/19) for lymphoblastic and 33.3% (30/90) for myeloblastic (P > 0.05). The platelet count of untreated patients with b3a2 isoform [(485.9 +/- 333.8) x 10(9)/L, n = 125] was distinctly higher than those with b2a2 isoform [(380.5 +/- 321.9) x 10(9)/L, n = 62] (P < 0.05). 66.0% (31/47) and 64.4% (29/45) of the patients in CP and AP/BP respectively co-expressed M- and m-bcr/abl transcripts (P > 0.05). One patient expressed only m-bcr/abl transcript was of typical acute myeloblastic leukemia (AML). Both two micro -bcr/abl(+) patients were of typical CML.

CONCLUSIONSAlmost all typical CML patients express M-bcr/abl transcripts, most of them coexpress M-bcr/abl and m-bcr/abl transcripts, a few possesses only micro -bcr/abl fusion gene. m-bcr/abl(+) are usually associated with AML or CML in myeloblastic crisis besides acute lymphoblastic leukemia (ALL). Patients with b3a2 isoform are prone to higher platelet count before treatment.