Genetic and genomic testing: what a result can tell you

Genetic testing is powerful, increasingly available, and frequently misunderstood.

The central misunderstanding is treating a probability as a prediction.

What these tests actually examine

• Single gene tests look at one specific gene.
• Panels examine a group of related genes.
• Broader sequencing examines far more.
• Some tests look at tumour tissue rather than inherited material.
• These answer different questions entirely.

Risk is not destiny

• Most results describe altered probability.
• Other genes, environment and chance all contribute.
• Many people with a risk variant never develop the condition.
• Many people with the condition have no identified variant.
• Ask what the number actually means for you.

Counselling before testing

• Discuss what each possible result would mean.
• Discuss what you would do differently.
• Discuss implications for relatives.
• Discuss possible insurance or employment implications locally.
• Counselling afterwards is far less useful than counselling before.

The question worth answering first

What would change as a result of this test?

• Would it alter treatment?
• Would it alter screening?
• Would it alter decisions about family?
• Would it only produce information?
• Information without a decision attached can still be burdensome.

Uncertain results are common

• Variants of uncertain significance occur frequently.
• They mean the finding cannot currently be interpreted.
• Classification can change over years.
• Ask how you would be informed of a reclassification.
• Expect this possibility before testing, not after.

Implications for relatives

• Relatives share genetic material with you.
• A result may be relevant to them.
• Consider in advance who you would tell.
• Some may not wish to know.
• Counselling services can help with these conversations.
• This is often the hardest part.

Testing children

• Generally reserved for conditions where childhood action is needed.
• Testing for adult-onset conditions is usually deferred.
• This preserves the child's future choice.
• Discuss it with a genetics service rather than assuming.

Direct-to-consumer tests

• They vary widely in scope and quality.
• They often examine only selected variants.
• A reassuring result may not exclude risk.
• An alarming result may be a false positive.
• Do not act clinically without confirmation.
• Take any concerning result to a clinician.

Ancestry products and health claims

• Ancestry analysis and health risk analysis are different things.
• Health features may be limited or unvalidated.
• Check what is actually being tested.
• Check what happens to your sample and data afterwards.

Privacy

• Genetic data is identifying by nature.
• Ask who stores it and for how long.
• Ask whether it is shared or used for research.
• Ask whether you can withdraw it.
• Read the consent text rather than accepting it.

Insurance and employment

• Rules differ substantially between countries.
• Ask whether results must be disclosed locally.
• Ask whether they can affect future cover.
• Check this before testing, not afterwards.

Population screening versus targeted testing

• Targeted testing follows a personal or family history.
• Broad population screening is a different proposition.
• Ask which one you are being offered.
• Ask what the evidence is for offering it to someone like you.
• The two have very different rates of useful findings.

Tumour testing is different

• Testing tumour tissue guides treatment selection.
• It usually says nothing about inherited risk.
• Ask which type of test is being proposed.
• Ask whether inherited findings could emerge incidentally.
• Ask what would happen if they did.

Timing the test

• There is rarely a reason to rush an inherited-risk test.
• Consider what else is happening in your life.
• Consider whether you have support around you.
• Consider whether you want the information now or later.
• Deferring is a legitimate choice, not avoidance.

Which laboratory performs it

• Ask whether the laboratory is accredited.
• Ask how variants are classified there.
• Ask whether results are reviewed by a clinical geneticist.
• Ask whether the report will be understandable to your local doctor.
• A cheap test with an uninterpretable report is not cheap.

Receiving the result

• Arrange to hear it with someone present if you wish.
• Ask for the explanation in plain language.
• Ask what it changes in practice.
• Ask what it does not tell you.
• Take the written report away with you.

Emotional impact

• Results can affect people unexpectedly, in either direction.
• Relief and guilt often arrive together in families.
• Ask what support is available.
• Ask whether patient organisations exist for the condition.
• Give yourself time before making major decisions.

Keeping the report

• Store the written report with your permanent records.
• Note which laboratory performed it and when.
• Note the exact variant named.
• Relatives may need these details years later.
• Laboratories do not keep records indefinitely.

After a positive result

• Ask what surveillance is recommended.
• Ask what preventive options exist.
• Ask what the evidence for each is.
• Do not rush irreversible decisions.
• Ask for support in telling relatives.

The cost side

• Ask the full price before agreeing.
• Ask whether counselling is included.
• Ask whether follow-up testing is included.
• Ask whether relatives would pay separately.
• Ask whether insurance covers any of it locally.
• The test is often the cheapest part of what follows.

Reproductive implications

• Some results affect decisions about having children.
• Options vary by country and by law.
• Discuss these with a genetics service, not informally.
• Partners may wish to be tested too.
• Take time; these decisions should not be rushed.

After a negative result

• Ask exactly what has been excluded.
• A negative result rarely excludes all risk.
• Ask whether usual screening still applies.
• Do not abandon routine precautions.

The point to remember

Three things:

1. Ask what would change as a result before testing.
2. Uncertain results are common — expect the possibility in advance.
3. Results affect relatives — plan those conversations before testing, not after.

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