Introduction: One hundred-and-six adult cases of acute lymphoblastic leukemia were prospectively investigated using a highly sensitive interphase fluorescence in situ hybridization assay which utilizes DNA probes that detect a double BCR/ABL fusion signal (D-FISH) in cells carrying the t(9;22) to evaluate the reliability and specificity of this method for the detection of the Ph translocation. The results were compared with those obtained in the same cases by conventional cytogenetics and by reverse-transcription polymerase chain reaction.
Materials and methods: The study was performed using DNA probes that span the common breakpoints of the t(9;22) translocation and that detect a double BCR/ABL fusion in cells carrying this karyotypic anomaly, one on the abnormal chromosome 9 and one on the Ph chromosome.
Results: Interphase D-FISH detected a high number of rearranged cases (22/106) compared to conventional cytogenetics (15/106) and RT-PCR (21/106).
Conclusion: Interphase D-FISH emerges as a reliable, fast and relatively inexpensive tool for the detection of BCR/ABL rearrangements in adult ALL patients at diagnosis. It has a sensitivity clearly higher than conventional karyotyping and it may prove also superior to that of RT-PCR in cases with unusual BCR/ABL breakpoints. Our results suggest that D-FISH might be considered as the initial test for the diagnosis of Ph+ adult ALL.