Molecular diagnostics: techniques and recommendations for 1p/19q assessment

Abstract

Several morphology- and polymerase chain reaction (PCR)-based methods for chromosome 1p 19q deletion status assessment are available. Important prerequisites for all molecular techniques concern tissue quality and selection of regions of interest. The most common methods for diagnostic 1p 19q assessment are fluorescence in situ hybridization and PCR-based microsatellite analysis. While the latter requires the use of autologous blood samples, more advanced techniques such as array comparative genomic hybridization, multiplex ligation-dependent probe amplification or real-time PCR are independent from autologous DNA samples. However, due to high technical demand and experience required their applicability as diagnostic tests remains to be shown. On the other hand, chromogenic in situ hybridization evolves as attractive alternative to FISH. Herein, the available test methods are reviewed and outlined, their advantages and drawbacks being discussed in detail.

Keywords: 1p 19q deletion; analytical performance; clinical performance; oligodendroglial tumors.

Figure 1.. Evaluated regions on chromosome 1.

aCGH: Array comparative genomic hybridization; CISH: Chromogenic in situ hybridization; LOH: Loss of heterozygosity; MLPA: Multiplex ligation-dependent probe amplification.

Figure 2.. Evaluated regions on chromosome 19.

aCGH: Array comparative genomic hybridization; CISH: Chromogenic in situ hybridization; LOH: Loss of heterozygosity; MLPA: Multiplex ligation-dependent probe amplification.

Figure 3.. Representative 1p 19q FISH images.

Target signal: red; control signal: green; DAPI counterstained. (A) Normal diploid signal ratio (2 controls/2 targets), magnification 63×. (B) Deletion status (signal ratio 2 controls/1 target), magnification 63×. (C) Imbalance with relative loss (4 control/2 target signals), magnification 63×. (D) FISH on a 4-micron-thick tissue section (magnification 40×) displaying a case with deletion status (signal ratio 2 controls/1 target) of the majority of nuclei.