Enhanced detection of chromosomal abnormalities with the use of RxFISH multicolor banding technique

Hematological disorders often have complex karyotypes with multiple markers , Proper assignment of chromosome number or aberration or both can be diffi cult. Specific identification of chromosomal abnormalities aids in the diag nosis and selection of treatment of patients. Fluorescence in situ hybridiz ation (FISH) has been applied to the identification of translocations, mark ers, and other chromosomal abnormalities in clinical cytogenetics. However, the standard FISH technique is unable to detect the entire genome in a sin gle experiment. This report presents the use of a cross-species comparative genomic hybridization color-banding technique (RxFISH) that permits examin ation of an entire karyotype at one time. Specimens from two patients, one with acute lymphocytic leukemia (ALL) and the other with multiple myeloma ( MM), were studied. Metaphases were prepared by standard culture techniques. Conventional cytogenetic analysis (GTG bonding) showed multiple clones in each of the cases. These clones were hyperdiploid metaphases rr with comple x chromosomal abnormalities and multiple markers. The slides were then hybr idized with FITC-, Cy-3-, and Cy-5-labeled RxFISH probes; the results were analyzed by a digital imaging system. The RxFISH color banding confirmed th e hyperdiploid metaphases and identified multiple chromosomal abnormalities . In the specimen from the patient with ALL, several chromosomes, which had been classified as markers by G-banding, were found to be specific chromos omes. This study suggests that RxFISH con provide more accurate and specifi c identification of complex chromosomal abnormalities. RxFISH is a useful c omplement to the clinical cytogenetic laboratory armamentarium. (C) Elsevie r Science Inc., 2000. All rights reserved.