What are Molecular Diagnostics?

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  • Written By: S. Gadd
  • Edited By: Heather Bailey
  • Last Modified Date: 01 October 2019
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Molecular diagnostics can be widely defined as the measurement of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), proteins, or other metabolites to detect certain genotypes, mutations, or biochemical changes that may be associated with certain states of health or disease. The emergence of molecular diagnostics is due to advances in biology that have resulted in an understanding of the mechanisms of normal and disease processes at the molecular level. Prior to this understanding, many disease states were diagnosed from morphologic observations.

The first widely used molecular tests were for infectious diseases, such as for hepatitis B and C or human papillomavirus (HPV), and this continues to be the largest molecular diagnostics market. Certain other fields, such as molecular tests for oncology, inherited conditions, cardiovascular disease, neurological disorders, and forensic testing, are rapidly growing areas of interest. Additionally, molecular diagnostics can be used to monitor a patient’s response to a particular drug treatment.


Many different biological techniques fall under the “molecular diagnostics” umbrella. One of the most common techniques is the polymerase chain reaction (PCR), a method of producing large amounts of specifically defined DNA or RNA fragments that can then be used for multiple purposes, including pathogen identification and detection of aberrant gene expression associated with certain diseases. PCR fragments may also be sequenced to detect gene mutations connected to certain disease states, such as the detection of mutations in the BRCA1 and BRCA2 genes that are often associated with an increased risk of hereditary breast cancer and ovarian cancer.

Another widely used technique is cytogenetic analysis, which involves the examination of chromosomes to diagnose or screen for certain genetic diseases or abnormalities. This technique is often used in oncology. By using known genetic markers, it is possible to detect the presence of cancer cells within a biological sample. Additionally, cytogenetic analysis of tumor samples can often give information regarding tumor aggressiveness or likelihood of tumor recurrence. Cytogenetic analysis is also useful in prenatal genetic testing to screen for a particular birth defect or chromosomal abnormality in the fetus.

The most anticipated development from molecular diagnostics is the concept of personalized medicine, which refers to the ability to tailor a treatment plan specifically to an individual based on his or her genetic makeup. This would identify patients who may respond well to a particular drug, and help to avoid adverse drug effects. In addition, it would determine a person’s risk for particular diseases prior to developing the disease. This concept is already being used to a certain extent to identify people who are prone to some gene-based diseases, such as cystic fibrosis, certain cancers, and Alzheimer’s disease.


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