The London General Practice genetic testing genomics and which test is suitable for you
WHAT IS GENETIC TESTING?
Genetic testing looks for changes in your DNA that can inform your medical care. These are sometimes called mutations or variants in your DNA.
Genetic testing can be used in many areas of medicine and can change the medical care which you or your family member receives.
For example, genetic testing can provide a diagnosis for a genetic condition such as Fragile X, or information about your risk to develop cancer.
There are various types of genetic tests but usually they involve a sample of spit. The results are generally available within a few weeks.
Genetic counselling before and after genetic testing is essential as DNA is shared within family members and if you are found to have a genetic change then your family member may have the same change.
It is also important that you have the right genetic test, that you are the right person in the family to have the genetic test and that the implications of the results are informed.
WHAT MIGHT THE REASONS FOR A GENETIC TEST BE?
- To learn whether you have a genetic condition that runs in your family before you have symptoms.
- To learn about the chance a current or future pregnancy will have a genetic condition.
- To diagnose a genetic condition if you or your child has symptoms.
- To understand and guide your cancer prevention or treatment plan.
WHAT TYPES OF GENETIC TESTS ARE THERE?
There are various different types of genetic tests and no single genetic test can detect all genetic conditions.
At The London General Practice genetic testing is individualised based on your medical and family history and what conditions you are being tested for.
Single Gene Testing
Single gene tests look for changes in only one gene.
This is done when it is thought that you or your child have symptoms of a specific condition or syndrome, for example, Duchenne muscular dystrophy or sickle cell disease. Single gene testing can also be performed when there is a known genetic mutation in a family.
For example, a genetic panel could look at low muscle tone, short stature or epilepsy.
They can also be grouped into genes that are associated with a high risk of developing certain kinds of cancer like breast or colorectal cancers, for example, the BRCA1 and BRCA2 genes.
Large Scale Genetic or Genomic Testing
This looks at all the genes in the DNA (whole exome) or just the genes that are related to medical conditions (clinical exome).
This is the largest genetic test and looks at all a person’s DNA, not just the genes.
This exome or genome sequencing can be ordered if you have complex medical histories.
Genome sequencing can lead to a personalised patient management plan which will tailor your healthcare, improve disease prevention, prediction, diagnosis and treatment.
All diseases result from a combination of genetic and environmental factors.
Common disorders such as diabetes, obesity, heart disease and most cancers are all influenced by underlying susceptibility as well as the surrounding environment and lifestyle that has been chosen to be adopted.
Clearly, background public health measures and general health promotions are keys to better health at population level, but at the personalised medical level, it is likely that prevention for example diet or weight loss programmes will also become increasingly tailored to a particular patient and interventions such as breast or prostate screening may be offered according to underlying risk.
TESTING FOR CHANGES AND OTHER GENE CHANGES
DNA material is packaged into chromosomes some of these tests look for changes in these rather than gene changes. For example, these tests are karyotype and chromosomal microarrays.
Genes are expressed or turned on at different levels in different types of cells. Gene expression tests compare these levels between normal cells and diseased cells because knowing about the difference can provide important information for treating the disease. For example, these tests can be used to guide chemotherapy treatment for breast cancer.
UNDERSTANDING GENETIC TEST RESULTS
Results can be
- Positive – the test found a genetic change known to cause disease.
- Negative – The tests did not find a genetic change known to cause disease.
This can be a false negative because either the wrong test has been ordered or there is not a genetic cause for the person’s symptoms or a true negative when there is a known genetic change in the family and the person tested did not inherit it.
If the results are negative and there is no known genetic change in the family, the negative test result may not give a definitive answer. This may be because the genetic change is not as yet known or you have not been tested for it.
- Uncertain – a variant of uncertain or uncertain significance means there is not enough information about that genetic change at present to determine whether it is benign as in a normal result or pathogenic causing a disease.
Here at The London General Practice we are evaluating all the current available genetic tests and matching these against the clinical evidence for them, the reliability of the results and the laboratory.
If you have a family history of a genetic condition, have symptoms of a genetic condition or are interested in learning about your chance of having a genetic condition, please enquire with us which tests might be suitable.
We are also looking at preventative tests with full genome sequencing so that you can actually change your lifestyle to prevent a disease.