Molecular Diagnostic Methods and Techniques
Molecular diagnostic methods detect and characterize disease at the level of nucleic acids and other molecules, rather than through cell or tissue morphology alone. This area orients the reader to the major laboratory technologies of molecular pathology — amplification, sequencing, hybridization, quantitative analysis, and the sampling of circulating biomarkers — and to how each turns a biological sample into a molecular readout.
Definition
Molecular diagnostic techniques are laboratory methods that identify, amplify, sequence, quantify, or localize specific nucleic acid sequences (and related molecules) to characterize the molecular basis of disease.
Scope
The area gives a high-level map of the techniques used in molecular pathology and groups them into five topics: nucleic acid amplification, DNA and RNA sequencing, cytogenetic and FISH methods, real-time quantitative and copy-number analysis, and liquid biopsy. It frames these as methodological reference material, not as protocols or clinical guidance.
Sub-topics
Key concepts
- Nucleic acid amplification
- DNA and RNA sequencing
- Hybridization and in situ detection
- Quantification and copy-number analysis
- Circulating biomarkers and liquid biopsy
- Analytical sensitivity and specificity
Mechanisms
Across this area, methods share a common arc: a target nucleic acid is captured or extracted, then selectively amplified, hybridized, sequenced, or quantified to produce a measurable signal. Amplification techniques such as the polymerase chain reaction make rare sequences detectable (Saiki et al., 1985); sequencing reads the order of bases either by chain termination (Sanger et al., 1977) or by massively parallel platforms (Goodwin et al., 2016); hybridization-based methods localize sequences within cells or chromosomes; and quantitative methods estimate how much of a target is present. Liquid biopsy extends these tools to nucleic acids shed into blood and other fluids (Wan et al., 2017).
Clinical relevance
Molecular diagnostic techniques underpin much of contemporary diagnostic pathology, from detecting pathogens to characterizing tumors. This entry describes the technologies as a reference framework for understanding how molecular results are generated; it is not a guide to ordering, interpreting, or acting on any specific test in patient care.
Evidence & guidelines
The methods in this area are supported by a large primary and review literature spanning the foundational descriptions of PCR and Sanger sequencing through modern next-generation sequencing and circulating-tumor-DNA reviews (Saiki et al., 1985; Sanger et al., 1977; Goodwin et al., 2016; Wan et al., 2017). Detailed reporting standards and consensus recommendations are discussed within the individual topic entries.
History
Molecular diagnostics grew from the convergence of recombinant DNA technology in the 1970s, Sanger's chain-termination sequencing (1977), and the invention of PCR in the mid-1980s (Saiki et al., 1985). The subsequent decades added real-time quantitative PCR, fluorescence in situ hybridization, microarrays, and high-throughput sequencing, broadening the field from single-gene assays to genome-scale analysis (Goodwin et al., 2016) and, more recently, to minimally invasive liquid biopsy (Wan et al., 2017).
Key figures
- Kary Mullis
- Frederick Sanger
- Russell Higuchi
Related topics
Seminal works
- saiki-1985
- sanger-1977
- goodwin-2016
Frequently asked questions
- What distinguishes molecular diagnostics from conventional pathology?
- Conventional pathology relies largely on the appearance of cells and tissues, whereas molecular diagnostics detects and characterizes specific nucleic acid sequences and molecular alterations directly, often revealing changes that are invisible under the microscope.
- What are the main families of molecular diagnostic techniques?
- They include nucleic acid amplification, DNA and RNA sequencing, cytogenetic and in situ hybridization methods, real-time quantitative and copy-number analysis, and the analysis of circulating biomarkers through liquid biopsy.