Comparison of Diagnostic Yield Among Multiplex Fluorescent in Situ Hybridization, Fluorescent in Situ Hybridization Probe Panel and Conventional Cytogenetic Studies in Acute Myeloid Leukemia

Conventional cytogenetic studies have been the gold standard for more than five decades for detecting genetic alterations that are greater than 10 Mb (mega base pairs) in size. Conventional cytogenetic studies have paved the way in identifying specific chromosomal aberrations associated with clinically and morphologically definitive subsets of hematological neoplasms.

Fluorescence in situ hybridization (FISH) has become a reliable and rapid complementary test in targeting critical genetic events associated with diagnostics and prognosis in hematological neoplasms.

In the current health care environment, which increasingly focuses on value and efficiency, it is critical for pathologists and clinicians to effectively navigate this environment and judiciously incorporate these high-complexity and expensive techniques into routine patient care. While conventional karyotyping provides a comprehensive view of the genome, FISH can detect cryptic or submicroscopic genetic abnormalities and identify recurrent genetic abnormalities in nondividing cells. As a consequence, it is commonly extrapolated that FISH will improve the sensitivity of detecting all genetic abnormalities compared with conventional karyotyping analysis. This assumption has then been translated in clinical practice to having clinicians and pathologists routinely ordering both conventional karyotyping and FISH studies in patients with hematological neoplasms. Depending on how comprehensive the FISH panel is, the cost for this testing may be quite expensive, and its additive value remains questionable.

It is common practice for laboratories to use FISH panels in conjunction with karyotyping both in diagnostic specimens and during follow-up to monitor response to therapy.

Multiplex FISH (M-FISH) represents one of the most significant developments in molecular cytogenetics of the past decade. In tumor and leukemia cytogenetics, two groups have been targeted by M-FISH to identify cryptic chromosome rearrangements not detectable by conventional cytogenetic studies: those with an apparently normal karyotype (suspected of harboring small rearrangements not detectable by conventional cytogenetics) and those with a complex aberrant karyotype (which are difficult to karyotype accurately due to the sheer number of aberrations).