Molecular testing is now considered the standard of care to screen for disease, confirm the diagnosis, guide management, and use target therapy. Currently, several testing strategies are being used. One of the most common strategies is single-gene testing, which is often conducted for known mutations, such as BRAF in melanoma and EGFR in lung cancer. Subsequently, next-generation sequencing (NGS), which tests many genes simultaneously, was developed using targeted gene panels, whole-exome, or whole-genome sequencing. Ordering the best diagnostic tool and choosing between single-gene testing and NGS depends on several factors. In this review, we discuss different single-gene testing methodologies and the impact of using them in comparison to NGS/multigene panel.
Choosing between single-gene testing and NGS depends on several clinical, analytical, and economic factors.
Communication with the ordering clinician, knowing the main purpose for the required molecular testing, and understanding the laboratory potentialities, help in determining the appropriate and most suitable technique.
Each methodology has its own advantages and disadvantages.
The implementation of molecular profiling enhanced the field of oncology and precision medicine. Twenty-four years after the discovery of DNA by Watson and Crick in 1953, Fredrick Sanger developed the dideoxy sequencing method in 1977 to sequence the first full genome.
This was followed by the introduction of the polymerase chain reaction (PCR) in 1983 allowing the analysis of small amounts of DNA and RNA. PCR revolutionized molecular diagnostics and led to an explosion in the number of new single-gene assays, which are tests that identify disease-associated genetic variants in a single target. PCR-based molecular testing frequently used capillary electrophoresis and hybridization with sequence-specific probes, and single-gene testing remained an excellent and dominant option for the next 3 decades. In 2005, next-generation sequencing (NGS) technology was developed and provided the ability to sequence multiple genes simultaneously using one sample. Later, the US Food and Drug Administration (FDA) approved NGS for clinical applications, leading to the introduction of competing platforms and a dramatic drop in the cost of DNA and RNA sequencing. During this genomic era, characterized by a wide variety of molecular technologies and extensive demand for mutation profiling, there remains significant uncertainty about the most practical and cost-effective approaches for a laboratory to adopt. Several considerations may be taken into account when deciding which molecular diagnostic tools to implement. In this review, we evaluate several single-gene testing options with regard to clinical indications, utilities, advantages, and limitations.