What is genetic testing?

What does genetic testing involve?

• Genetic testing involves carrying out a range of tests on samples of DNA taken from blood, hair, skin, saliva, amniotic fluid (the fluid that surrounds the baby during pregnancy) and other tissues.
• The DNA sample is then sent to the laboratory where scientists look for specific changes in the DNA to find and identify any genetic disorders.
• The laboratory results are then sent in writing to the individual’s doctor or genetic counsellor so that they can discuss them with the patient.
• There are currently more than 2,000 genetic tests in use and more are in development.

Why is genetic testing needed?

• A genetic test is generally performed in a particular individual or family for a specific medical purpose.
• There are a number of reasons why a genetic test may be called for, these include:
  • Pre-implantation genetic diagnosis (PGD): Screening an embryo for a genetic disease
  • Prenatal testing: finding a genetic disease in an unborn baby
  • Carrier testing: finding out if parents carry a genetic mutation that they could pass onto their future children
  • Predictive genetic testing: testing an adult for a genetic disease before they have symptoms, usually where the disease runs in the family and they want to find out if they may also be affected
  • Diagnostic genetic testing: making a diagnosis in a patient that is showing symptoms of a known genetic disease
  • Pharmacogenetic testing: determining the best dose or type of medicine to give an individual patient based on their genetics.

The results

• Before a person has a genetic test, it is considered essential that they understand the benefits and limitations of the tests, as well as the possible consequences of the results.
• The results of genetic testing may bring with them the need to make important, life-changing decisions.
• For example, if parents find they have a high chance of passing on a genetic condition to their children, they must decide whether or not they should try for a baby.
• As a result, genetic testing goes hand-in-hand with genetic counselling, both before and after testing.
• Genetic counselling:
  • helps prepare people for the potential outcomes of a genetic test
  • helps patients to understand the results once they receive them
  • gives patients the opportunity to talk through their concerns and make informed decisions about what their next steps are going to be.

Direct-to-consumer testing

• More recently genetic tests have been made available over the internet for individuals wanting to know more about their genetics, ancestry and future health.
• This type of genetic testing does not generally involve medical consultation or a genetic counsellor unless the individual seeks it out themselves.
• The results from the test are generally substantially less predictive than medical genetic testing, and are given directly to the consumer.