Family history and what to do with it

Family history is among the cheapest pieces of clinical information available and one of the most consistently incomplete in medical records.

Why it matters

It changes decisions in several concrete ways.

It alters cardiovascular risk calculations, with premature disease in a first-degree relative being a specific factor.

It changes cancer screening: earlier starting ages and shorter intervals apply to people with certain family histories, and some qualify for entirely different surveillance programmes.

It identifies candidates for genetic testing, where an inherited condition would change management for the person and for their relatives.

And it prompts consideration of conditions that would otherwise not be looked for.

What to collect

Specific rather than general.

For each first-degree relative — parents, siblings, children — and second-degree relatives where possible: what conditions they had, at what age they were diagnosed, and if deceased, the cause and age at death.

Age at diagnosis is the detail that matters most and is the one usually missing.

Ethnic background, since several conditions have markedly different prevalence between populations.

Consanguinity, where relevant.

And whether any relative has had genetic testing, which can save considerable time.

The patterns that warrant referral

Where a genetics assessment may be appropriate.

Several relatives on the same side with the same or related cancers.

Cancer diagnosed at unusually young ages.

Bilateral disease, or multiple primary cancers in one person.

Specific combinations: breast and ovarian; bowel and endometrial; and certain rarer clusters.

Male breast cancer.

Known pathogenic variants in the family.

Premature cardiovascular disease — commonly defined as under fifty-five in men and sixty-five in women.

Sudden unexplained cardiac death in a young relative, which warrants family assessment for inherited arrhythmia and cardiomyopathy syndromes.

Very high cholesterol in the family, which may indicate familial hypercholesterolaemia — a condition affecting a meaningful proportion of the population, substantially underdiagnosed, and where early treatment transforms outcomes.

And several relatives with the same condition of any kind.

What genetic testing involves

Where it is indicated.

Assessment by a genetics service, which begins with a detailed family tree rather than a test.

Testing an affected relative first where possible, since a negative result in an unaffected person is uninterpretable unless the family variant is known.

Counselling about implications, which cover screening, preventive options, family members and, in some jurisdictions, insurance.

And results that may be positive, negative or a variant of uncertain significance, which is a common and frustrating outcome.

Direct-to-consumer genetic testing

Where the limitations are substantial.

Consumer tests typically examine a selected set of variants rather than sequencing entire genes, which means a negative result does not exclude an inherited condition.

Regulatory and professional bodies have raised concerns about both false reassurance and unnecessary alarm.

Raw data reinterpreted by third-party services has a documented rate of false positives, and clinical services generally will not act on such results without confirmatory testing.

Health-related findings from these tests frequently generate clinical workload and anxiety without changing management.

Which does not mean they are worthless, and it means that a strong family history should go to a clinical genetics service rather than to a consumer kit.

What to do with a strong history

Practical steps.

Write it down properly, with names, relationships, conditions and ages.

Bring it to a clinician and ask specifically whether it changes your screening or risk assessment.

Ask about earlier or additional screening where relevant, since eligibility is frequently not offered automatically.

Address the modifiable risk factors, which matter more in people with elevated inherited risk rather than less.

And share the information with relatives, since inherited risk is a family matter and the person who gathers it is frequently the only one who has.

What a family history does not mean

Worth stating.

A condition in a relative does not mean you will develop it.

Most common diseases are multifactorial, with genetic contributions that are modest individually.

Shared environment and behaviour account for a substantial part of familial clustering — families share diet, activity, smoking and socioeconomic circumstances as well as genes.

Which means that a family history of type 2 diabetes or cardiovascular disease is a prompt to act on the modifiable factors rather than a verdict.

The conditions worth asking about specifically

Where family history changes practice.

Cardiovascular disease and sudden cardiac death.

Breast, ovarian, bowel, prostate and pancreatic cancer.

Familial hypercholesterolaemia.

Glaucoma, where first-degree relatives are at markedly higher risk and are frequently entitled to free testing.

Type 1 and type 2 diabetes.

Osteoporosis and hip fracture.

Haemochromatosis.

Inflammatory bowel disease and coeliac disease.

And mental health conditions, which are relevant to assessment and to threshold for seeking help.

General information only, not medical advice. Consult a qualified clinician about your family history and whether it changes your screening or risk assessment.