Healthcare Professional Glossary of Terms
Chromosomal Microarray Analysis
Microarray-based genome-wide copy number analysis used for the identification of copy number variants.
CNV, Copy Number Variants
Copy Number Variants are sub-microscopic chromosomal duplications and deletions (losses or gains of genetic material in comparison to the reference genome). CNVs may be inherited from a parent, or appear as “de novo” (please see the description of a De novo Variant). CNVs may be common or rare. Rare pathogenic CNVs in specific chromosomal regions (e.g. 22q11.2) can confer substantial risk for brain (intellectual disability, autism spectrum disorder, schizophrenia) and other medical disorders.
De novo Variant
Genetic variant that was not inherited from either parent. It is the result of a spontaneous change in the DNA sequence that arose in the germ cell (egg or sperm) of one of the parents or in the fertilized egg. The individual with the de novo variant is the first in his/her family to carry this variant.
Diagnostic Genetic Testing
Genetic testing in an individual who displays symptoms (patient) in order to either confirm/ establish/rule out a clinical/differential diagnosis.
Sequencing of the entire protein coding regions in a genome (known as the exome). Genome refers to each individual’s entire genetic information.
Genetic counselling is a communication process that helps patients and their families to effectively use (new) genetic information. It aims at improving patient knowledge, perception of risk and autonomy in decision-making (e.g. agreeing to or declining genetic testing) as well as decreasing stigma experienced. Genetic counselling is not dependent on genetic testing. However, whenever genetic testing is offered, it should include genetic counselling.
Sequencing of a specific set of genes/gene regions (e.g. 100 genes) rather than sequencing the entire exome or genome. In the clinical context, gene panels include genes that are known to be causal for a specific diagnosis/symptom (e.g. familial cancer syndrome; epilepsy).
Polygenic Risk Score
The Polygenic Risk Score (PRS) is constructed using information from common variants (single nucleotide polymorphism, SNPs) identified in genome-wide association studies. It sums up the information from trait/disorder-associated SNPs weighted by their effect sizes. PRS are a measure of an individual’s liability to a given trait or disorder. Currently, these risk scores do not have high levels of precision and have therefore no current clinical utility in psychiatry.
Predictive testing is currently not offered for psychiatric disorders. It refers to genetic testing in a presymptomatic individual at risk of developing a genetic disorder due to a positive family history. The genetic test results informs the patients and the clinician on whether or not the individual is likely to/will develop a specific genetic disorder.
Whole Genome Sequencing
Sequencing of the entire DNA sequence (genome) of an individual.