Genetic tests can provide information that can be used for a variety reasons, such as for health, lifestyle and ancestry. This section covers the different kinds of health-related genetic tests.
Diagnostic genetic tests are used to confirm a suspected diagnosis in a person that may be showing clinical symptoms of a condition or disease. Testing is not available for all genes or all genetic conditions. For those that are available, the results of a diagnostic test can influence a person’s choices about their health and management of the disease.
Genetic carrier tests are used to determine if a person ‘carries’ a mutation (faulty gene copy) that is associated with a specific genetic condition. Being a carrier of the faulty gene does not usually affect the health of the person. However, if the person’s partner also carries the faulty gene, they have an increased chance of having a child with the condition. Genetic carrier testing may be offered if a person has a family history of the condition or has ancestry that puts them at increased risk for carrying the mutated gene.
Screening tests are used to in specific populations, usually to detect future disease risks in individuals or their children (current and future). Screening tests are used even in those who are not considered as being at increased risk of carrying a mutation. Screening of newborn babies for conditions such as cystic fibrosis is an example of a screening test that is used for the early identification of infants at risk for certain conditions. Where a screening test gives a positive result, further testing would be required before a diagnosis can be confirmed.
Predictive tests are used to find out if a person has inherited a genetic mutation (or a faulty copy of the gene) that is involved in a particular condition. If the result shows that the person has inherited a faulty gene, he or she may be at an increased chance of developing that condition later in life. Predictive tests cannot predict whether the person will definitely develop the condition in their lifetime. The tests are usually performed in a person who currently has no symptoms, when a family member has been diagnosed with a genetic condition that is known to be heritable. These tests can provide information that can lead a person to make healthier lifestyle choices and/or choose to get regular check-ups to help manage their risks. Predictive tests are performed for conditions such as some forms of cancer, including breast cancer, where a person has a strong family history and the genetic mutation has been identified in a blood relative.
Pre-symptomatic tests are used to determine if a person has inherited a mutation involved in a particular condition. These are used in a way similar to predictive genetic testing, except that inheriting the genetic mutation involved means that the person will develop the condition in their lifetime if they live long enough, e.g. Huntington disease.
Pharmacogenetic tests are used to predict how a person may react to a particular drug and dosage to help a doctor decide on the best treatment options.