Genetic And Genomic Testing

Overview

Genetic testing is a way of looking at your DNA — the set of instructions your body uses to grow and work. A gene is a short section of DNA that carries one set of instructions. Genomic testing looks at many genes, or sometimes all of your DNA, at once. These tests can help find the reason for a health condition, show whether a condition runs in your family, or help your care team choose the screening and care that suits you best. Testing is always your choice, and you can take your time to decide.

Genetic testing is becoming much more common. Millions of people have some form of it each year, from the newborn blood spot test offered to every baby to tests done during pregnancy and tests that help guide cancer treatment. Tests that read your whole genetic code are newer, but they are increasingly used in ordinary NHS care.

Anyone can be offered genetic testing. It may be suggested if you or your family have a condition that can run in families, if you are pregnant or planning a pregnancy, if you have a child with developmental or health concerns, or if you have a condition where testing helps guide treatment. Some people also buy home testing kits out of personal interest. Your age, background or family situation does not stop you from asking about testing.

Symptoms

Common symptoms

• Genetic testing is a test, not an illness, so it has no symptoms of its own.
• People often ask about testing after noticing a pattern in the family — several close relatives with the same condition, or a condition appearing at an unusually young age.
• Sometimes a GP or specialist suggests testing after a blood test, scan or examination points to a possible inherited cause.
• Some people have no symptoms at all and ask about testing simply because a relative has had a result.

Symptoms in children

• In the UK, every baby is offered the newborn blood spot test a few days after birth. It checks for a small number of rare but treatable conditions.
• Testing may be offered for a child with developmental delay, learning difficulties, birth differences or a condition that runs in the family.
• A parent or carer gives consent, and children are included in the conversation in a way that suits their age and understanding.
• Testing for conditions that only cause illness in adulthood is usually delayed until the young person is old enough to decide for themselves.

Symptoms in older adults

• Testing may be suggested if you develop a condition younger than usual, or if several relatives have had it.
• Results can sometimes guide which screening tests are most useful for you, and which treatments are likely to work best.
• A result can also help explain symptoms and give the whole family clearer information.
• Consent and clear explanation matter at every age — you can always ask for more time or say no.

Causes

Main causes

• Genes are passed down from parents to children. Small differences in genes are normal and are what make each of us unique.
• Some differences can affect how the body works and lead to a health condition. These may be inherited from a parent, or may appear for the first time in you.
• Some conditions are caused by a change in a single gene, others by changes in several genes combined with lifestyle and environment.
• Genetic testing is also used to look at changes in genes inside a tumour, which can help guide cancer treatment.
• Genomic testing reads many genes at once, which can be helpful when the picture is unclear or several conditions are possible.

Risk factors

• One or more close relatives with a condition known to run in families
• Several relatives with the same condition, or a condition appearing at an unusually young age
• A child with birth differences, developmental delay or learning difficulties
• A personal history of certain cancers, heart conditions or unusual blood test results
• Being from a family background where particular inherited conditions are more common
• Parents who are close blood relatives, which raises the chance of certain inherited conditions
• Being pregnant and wanting information about the baby's chance of certain conditions

When to see a doctor

See a doctor urgently if:

• You have a known inherited condition and your symptoms suddenly get worse or feel severe.
• You are unwell after any procedure used to collect a sample, with fever, heavy bleeding or severe pain.
• You feel overwhelmed, very anxious or very low about testing or your results and need support today.

Book a routine appointment if:

• One or more close relatives have a condition that can run in families and you want to know if testing is right for you.
• You are planning a pregnancy and want to talk about inherited conditions.
• You have bought a home genetic test and are unsure what the result means.
• You received a result some time ago and want to understand what follow-up you should have.
• You are worried about whether a result could affect insurance or employment and want advice.

Diagnosis

Genetic testing starts with a conversation, usually with your GP, a specialist doctor or a genetic counsellor — a health professional trained to explain what testing can and cannot tell you. They will ask about your health and your family's health, sometimes drawing a family tree, and explain which tests might help. If you choose to go ahead, you give consent and a sample is taken. Results are usually explained to you in a follow-up appointment, with time for your questions.

Tests that may be done

• A sample of blood, saliva or a cheek swab, which contains your DNA
• Single gene test — looks at one specific gene when a particular condition is suspected
• Gene panel — looks at a group of genes linked to a type of condition, for example inherited heart conditions
• Whole exome or whole genome sequencing — reads a large part or all of your genetic code when the picture is unclear
• Chromosome tests such as a karyotype or microarray — look at the number and arrangement of chromosomes, which are the packages that hold DNA
• Carrier testing — shows whether you carry a change that could affect a future child
• Prenatal tests during pregnancy, including the combined screening test, non-invasive prenatal testing, chorionic villus sampling and amniocentesis
• Newborn blood spot screening — offered to all babies a few days after birth
• Pharmacogenomic testing — checks how your body is likely to handle certain medicines
• Tumour (somatic) testing — looks at gene changes inside a cancer to help guide treatment

What to expect at your appointment

Before the test you should be told why it is being suggested, what it could find, and what the limits are. The sample itself is quick, usually like a routine blood test. Results take time — often a few weeks, sometimes several months for larger tests. You will then usually be invited to talk through the result. A result can be positive (a change was found), negative (no change found) or uncertain (a change was found whose meaning is not yet clear). Whichever it is, you are entitled to a clear explanation and time to decide what happens next.

Treatment

Genetic testing does not change your genes, and it does not always lead to treatment. What it can do is give you and your care team better information, so you can make choices that fit your situation. For some people, a result means extra screening or a change in follow-up. For others, it explains something that has been worrying them and needs no treatment at all. Your care team will make a plan with you that reflects your own health, your preferences and your family situation.

Self-care at home

• Ask for genetic counselling before and after testing — it is there to help you understand, not to push you into anything
• Keep a copy of your results in a safe place and share them with any doctor treating you
• Write down your questions between appointments so you do not forget them
• Take your time before deciding whether to test, and be clear about what you would want to know in advance
• Consider telling close relatives about a result that could affect them, and ask your genetics team how to do this
• Take care of your mental health while waiting — arrange things you enjoy and talk to people you trust
• If you used a home testing kit, bring the result to your GP rather than acting on it alone

Medical treatments

There is no treatment that changes the genes you were born with. Instead, the focus is on what the result makes possible. For some inherited conditions this means regular check-ups and screening, such as earlier or more frequent scans and blood tests. For others, it may mean specialist care from a heart, cancer or metabolic team. Some conditions respond to specific treatments — for example, dietary changes and specialist dietitian support for certain metabolic conditions, or treatments chosen to match how your body handles a medicine. Some inherited conditions have no specific treatment, and the value of testing lies in clearer information, planning and support. Your specialist team will explain the options for your situation and answer your questions.

When is surgery considered?

Surgery is not done to change your genes. In a small number of inherited conditions, an operation may be discussed to lower the chance of a particular cancer, or to treat a condition that has already been found. These decisions are never rushed: they are made after careful discussion with a specialist team, and they weigh up your own risks, your age, and what matters most to you. Some people decide against surgery, and that is a valid choice.

Living with this condition

Most people find that life carries on much as before after testing. A result may mean a few more appointments, or a reminder to keep up with screening. It may also prompt conversations with relatives. Some people think about their result often at first and less over time. It helps to know who to contact with questions, and to have a copy of your result ready for any new doctor or nurse you see.

Lifestyle tips

• Keep up with any screening, check-ups or tests your team recommends
• Tell your dentist, pharmacist and any new doctor about a result that affects your care
• Stay active and keep to general healthy living advice, which helps with many conditions that run in families
• Decide in advance how you would like relatives to be told, and ask your genetics team for help if that feels difficult
• Keep a simple folder or phone note of your results and appointments
• Build in time for things that help you unwind, especially around appointments

Diet and exercise

For most people, general healthy eating and regular movement are the most useful things you can do, and they help protect against many conditions that run in families. If you have an inherited condition that affects how your body uses food, such as some metabolic conditions, you may need specific dietary advice from a specialist dietitian, and you should follow the plan your team gives you rather than a general diet. Your GP or specialist can tell you what level and type of activity is safe for you.

Mental health and emotional wellbeing

It is very normal to feel anxious, sad, relieved or confused — sometimes all in one week. Waiting for results can be especially hard, and a result can bring up worries about yourself, your children or your relatives. These feelings usually settle with time and support. If low mood, worry or sleep problems are affecting your daily life, please tell your GP or genetics team; talking therapies and specialist counselling are available. If you ever feel you cannot cope or have thoughts of harming yourself, contact your local emergency number or a local crisis line straight away, and reach out to someone you trust.

Prevention

You cannot choose the genes you inherit, so testing is not something you need to prevent. What you can do is use the information to lower your risk of related illness — for example by taking up the screening you are offered, making healthy lifestyle changes, or discussing preventive options with your team. Testing is a choice, not an obligation, and choosing not to test is also a reasonable decision.

Vaccines

Some inherited conditions raise the risk of infections, and your care team may recommend certain routine vaccinations. Ask your GP or specialist which vaccinations are advised for you, and keep up to date with the ones offered to everyone.

Screening programmes

Screening is one of the main benefits of genetic testing. Depending on your result, you may be offered earlier, more frequent or extra screening, such as scans, blood tests or bowel checks. Close relatives may also be offered testing — sometimes called cascade testing — so they can make their own choices. In the UK, the newborn blood spot test and the screening tests offered in pregnancy are available to everyone. If you have a family history that worries you, ask your GP whether you meet the criteria for a referral to a genetics service.

Complications

If left untreated

• Without testing, an inherited condition may go unrecognised, and useful screening or follow-up may be missed.
• Relatives who could benefit from testing may not find out in time to make their own choices.
• Uncertainty can carry on causing worry when a clear answer might have been possible.
• Some inherited conditions, if not identified, can cause serious illness that earlier monitoring could have caught.

Long-term outlook

For most people, genetic testing brings useful clarity rather than bad news. Many people who are tested find nothing of concern. When something is found, it often means there are steps that can be taken — extra screening, earlier monitoring, or a treatment plan better matched to you. Genetic knowledge is growing quickly, and tests that are unclear today may be reclassified in the future. Whatever your result, you are entitled to clear information, support and time to decide what comes next, and your care team is there to help at each stage.

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