Why do we do genetic tests?

Testing our genomes can help identify the causes of genetic conditions, and plays a part in the prediction, prevention and treatment of certain conditions.

Why do we do genetic tests?

Some examples of how genomic testing can be used are:

Diagnostic testing: To confirm a diagnosis of a genetic condition.

  • Some rare diseases are caused by as little as a single base change, like a spelling mistake, in someone’s DNA. Looking at the genome of a person affected by a rare disease can help find which DNA changes might be causing the condition.


Predictive testing: To assess your chances of developing a genetic condition and to help choose care that can prevent or help reduce the effects of a condition.

  • For example, if your family has a known history of a genetic condition (such as an inherited cancer syndrome, or certain inherited heart conditions) you may be offered predictive testing (before you develop any symptoms). If you are then found to carry a genetic variant that increases your chances of a condition, you can be entered into screening programmes to detect any signs of the condition as early as possible or your doctor may talk about treatments or lifestyle changes that might prevent the condition.


Treatment decisions: For some patients, knowing more about their genome may mean that a particular treatment can be recommended.

  • In some circumstances, testing can also be used to predict which medications are likely to be most effective and cause the least side-effects for someone (also known as pharmacogenomics).

Tumour testing: Comparing the normal and cancer genomes may give clues about ways to treat the cancer.

  • In cancer, the tumour cells have developed a different genome to the healthy cells. Understanding these differences can help choose treatments. Find out more about genomics and cancer here.

Carrier testing: testing to see if there is a chance of passing specific genetic conditions onto children.

  • This may be available to multiple members of your family if there is a chance of passing specific genetic conditions onto children.
  • Examples of conditions where carrier testing is performed include cystic fibrosis or thalassaemia.


 Prenatal testing: Genetic tests can be used to diagnose conditions in your unborn baby.

  • These might include Down’s syndrome or other conditions known to affect your family. They may also be used to diagnose genetic conditions if unexpected problems are detected on prenatal ultrasound scans.

If you think you, or someone you know, needs a genomic test, you should speak to your GP or another healthcare professional. If they identify that a genomic test could be appropriate, they may then conduct the test or refer you to Clinician Genetic Services. It is not possible for patients to request a test directly from the Genomic Laboratories.

If you have been offered a genomic test, please read ‘What does a genetic test involve‘.

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