The role of fluorescence in situ hybridization technologies in molecular diagnostics and disease management

Large genomic changes, such as aneuploidy, deletions, and other chromosomal rearrangements, have long been associated with pregnancy loss, congenital abnormalities, and malignancy. These genomic changes are quantitative, unambiguous, and fundamental in the transition of normal cells to abnormal ones. Detection of these large genetic changes has an increasingly important role in determining patient diagnosis and care, including therapeutic selection. We have developed two major product platforms that assess genomic changes at various levels of resolution. Fluorescence in situ hybridization (FISH) techniques and the related technology of array-based comparative genomic hybridization (CGH) allow detection of genesized or larger alterations in the genome. FISH is a robust DNA probe technology that can measure both balanced and unbalanced genomic changes on a cell-by-cell basis. In most instances, it is not dependent on metaphase chromosomes, and it is widely used in clinical diagnostics. Array-based CGH has much greater multiplexing capabilities than FISH. This technology has the potential to examine many regions of the genome simultaneously for changes in DNA copy number and identify complex patterns of gains and losses within the genome. In this article, we review several of the current medical applications of FISH and discuss such advanced techniques as CGH and array-based CGH.