RAPID COMMUNICATION Improved Sensitivity of BCR-ABL Detection: A Triple-Probe Three-Color Fluorescence In Situ Hybridization System

Chronic myeloid leukemia is a clonal stem cell disorder assoprobe labeled with a different fluorochrome to create a triple-probe/three-color system that permits identification of ciated with the Philadelphia (Ph) translocation [t(9;22) (q34;q11)]. As a result of the Ph translocation, parts of the both the Ph chromosome and the derivative 9 chromosome in Ph cells. This system was used to determine the freABL and BCR genes become fused. Cytogenetic quantification of Ph metaphases can be used to monitor patient requency of interphase cells carrying the BCR-ABL fusion gene in bone marrow and peripheral blood granulocytes from pasponse to treatment but is of limited sensitivity and applies only to cycling cells. Fluorescence in situ hybridization (FISH) tients showing variable cytogenetic responses to interferon. Our data show that the triple-probe/three-color approach with probes from the BCR and ABL regions can also identify the Ph translocation in interphase cells. Established systems allows highly sensitive detection of residual disease. Moreover, this method is readily applicable to the analysis of for the detection of fusion genes by FISH rely on colocalization of two different probes but are associated with a high other chromosome translocations. q 1997 by The American Society of Hematology. rate of false-positive results. We have introduced a third