genomics

Genome sequencing as a diagnostic test

Author/s: 
Costain, G., Cohn, R. D., Scherer, S. W., Marshall, C. R.

KEY POINTS
Genome sequencing is a comprehensive genetic test that is being integrated into health care systems internationally.

Test indications include suspected genetic disorders in children and adults for whom a targeted genetic testing approach is likely to be low yield or has already failed.

Analytic validity, diagnostic yield and clinical utility are similar or superior to other clinical genetic tests, such as exome sequencing, chromosomal microarray analysis and next-generation sequencing gene panel tests.

Appropriate adoption of genome sequencing as a molecular diagnostic test in Canada would be facilitated by a cohesive national strategy for genomic medicine.

Genetic testing of patient constitutional DNA (i.e., their genome) is increasingly performed in medical practice. 1–3 Sequencing an entire human genome (about 3.2 billion nucleotides) is now possible to complete in days to weeks, and at a similar cost to some advanced imaging tests or to a brief admission to hospital.3,4 Genome sequencing is being integrated into health care systems internationally, most notably in the United Kingdom.5 Starting in 2021, genome sequencing is being performed as a clinical genetic test in Ontario, Canada.

What Are Polygenic Scores and Why Are They Important?

Author/s: 
Sugrue, Leo P., Desikan, Rahul S.

Mendelian disorders and monogenic traits result from combinations of variants in 1 or a few genes that have a large effect on the propensity for developing a certain disease or characteristic. In contrast, complex traits, such as eye color or cardiovascular disease, are determined by variations occurring in many genes that have smaller effect sizes and act over long periods of time, often in concert with environmental factors. The cumulative risk derived from aggregating contributions of the many DNA variants associated with a complex trait or disease is referred to as a polygenic risk score (also known as a genetic risk score). This JAMA Genomics and Precision Health article explains polygenic risk scores as determinants of an individual’s inherited risk for complex disease.

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