"Home-brew" FISH assay shows higher efficiency than BCR-ABL dual color, dual fusion probe in detecting microdeletions and complex rearrangements associated with t(9;22) in chronic myeloid leukemia.

We carried out fluorescence in situ hybridization (FISH) studies on 18 Ph+ chronic myeloid leukemia (CML) cases with chromosome 22 genomic deletions with the Vysis BCR-ABL dual-color/dual-fusion probe (BCR-ABL DC/DF) to compare the hybridization patterns obtained with this approach to those obtained with the "home brew" BAC/PAC system. Our results are the following: chromosome 22 microdeletions less than 400 kilobases (Kb) were not detected by the BCR DC/DF probe; FISH analysis with the BCR DC/DF probe in cases bearing chromosome 22 microdeletions ranging from 400 to 700 Kb produced a faint signal on the der(9); and the BCR-ABL DC/DF FISH pattern was comparable to the one obtained by the home brew probe in the presence of a 900-Kb chromosome 22 microdeletion. Our home-brew FISH system represents an accurate method for revealing a subset of CML patients with der(9) microdeletions.