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Feature Article

Genomics: what it means for patients and GPs

LISA EWANS, MARY-ANNE YOUNG
OPEN ACCESS

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© natali_mis/istockphoto.com
© natali_mis/istockphoto.com

Abstract

Genomics is an important emerging field in medicine that will have increasing relevance in general practice. This article outlines the current utility of genomics and provides information to enable discussion about the application of genomics.

Key Points

  • Over the past decade genomic testing has become more accessible and affordable with results available much sooner.
  • Genomic tests, particularly whole exome and whole genome sequencing, are now increasingly used to diagnose patients with Mendelian genetic diseases including syndromal intellectual disability, cardiac disease and cancer.
  • Genomic tests are more recently being used in preventive health. This includes pharmacogenomics testing and testing of healthy individuals for genes that are rare but significantly increase disease risk.
  • Patients’ genomic data will become more accessible in the future and is set to play an increasing role in guiding patient care.

The Human Genome Project, completed in 2003, was a combined global effort to map the human genome as a reference source.1 Tools developed during this project provided the catalyst for the subsequent significant advances in genomic technology to enable rapid and cheaper genome sequencing and improved interpretation of genomic data. The technology is often referred to as next generation sequencing (NGS) or massively parallel sequencing (MPS) and the term genomics refers to the use of this technology to sequence either the entire genome – whole genome sequencing (WGS) – or all the genes in the genome – whole exome sequencing (WES). 

The advantage of genomic technologies over more traditional genetic testing modalities is that WES and WGS allow for a broader diagnostic search for the underlying genetic cause in an individual suspected or known to have a genetic disease. Over the past decade, genomic sequencing has gone from being a research-based tool to a testing option that is being used widely in clinical practice.2

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Types of testing

Many different genetic tests are available and used in patient care for purposes ranging from diagnosis of rare genetic conditions to preconception carrier screening. Although Medicare rebates are available for some genetic tests (such as those for haemochromatosis and Fragile X syndrome), there is currently no Medicare rebate for many others, including genomic testing. The cost of the tests varies depending on which laboratory is offering the test and is largely determined by the technology used, the number of genes covered, the speed of the result and the country in which the laboratory is based. Patients seen through public clinical genetics services when offered testing usually have no out-of-pocket costs, which is an important consideration as some genetic test costs are high. 

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Single-gene and multi-gene panel tests

There is a wide range of genetic tests available, including single gene tests for conditions that have a single gene basis such as cystic fibrosis and tests for panels (groups) of genes known to be associated with specific genetic diseases or organ pathology that are genetically heterogeneous (i.e. could be caused by one of many genes). Laboratories are increasingly moving to gene panel testing via NGS to increase the number of genes tested and reduce costs. Gene panels commonly used include those for cardiac diseases such as cardiomyopathy, ocular disorders such as retinitis pigmentosa and neurological disorders such as epilepsy. 

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© natali_mis/istockphoto.com
© natali_mis/istockphoto.com
Dr Ewans is a Clinical Geneticist at Royal Prince Alfred Hospital, Sydney; a Genome Analyst at Genome.One, Sydney; and a PhD student at UNSW Sydney and the Garvan Institute of Medical Research, Sydney. Ms Young is the Head of Clinical Service Development at Genome.One, Sydney, NSW; and has more than 30 years clinical experience encompassing nursing, family therapy and genetic counselling. She is the immediate past President of the Human Genetics Society of Australasia.