When should relatives be screened for FH? 

Relatives should be screened for familial hypercholesterolaemia (FH) as soon as a family member (known as the index case) is diagnosed with the condition. This process, called cascade testing, is a clinical priority in the UK because each first-degree relative parents, siblings, and children has a 50% chance of inheriting the same genetic mutation. Identifying relatives early allows for life-saving treatment to begin before any significant damage to the arteries occurs. 

What We’ll Discuss in This Article 

• The clinical process of cascade testing for family members. 

• Why first-degree relatives are the primary priority for screening. 

• Recommended ages for testing children with a family history of FH. 

• The difference between genetic DNA screening and lipid testing for relatives. 

• When second-degree and third-degree relatives should be included. 

• How the British Heart Foundation (BHF) supports the UK screening network. 

• The role of the BMI Calculator in long-term cardiovascular monitoring. 

The Process of Cascade Testing 

In the UK, the screening of relatives is managed through a systematic process known as cascade testing. Once a person is confirmed to have FH, usually via a genetic test, their healthcare team will work with them to identify biological relatives who may also be at risk. This method is highly effective because it targets individuals with a known high probability of having the condition. 

The testing usually starts with first-degree relatives and only moves to second-degree relatives (such as aunts, uncles, or grandparents) if the first-degree relative also tests positive for the condition. 

Priority of Screening 

Relative Category	Examples	Priority Level
First-Degree	Parents, Siblings, Children	Immediate / Highest
Second-Degree	Grandparents, Aunts, Uncles, Nephews	High (if parent is positive)
Third-Degree	First Cousins, Great-Grandparents	Standard (if lineage is positive)

Recommended Age for Screening Children 

A critical question for many families is when children should be tested. Because the effects of FH begin at birth, identifying the condition in childhood is essential for lifelong protection. In the UK, current clinical standards recommend that if a parent has a confirmed diagnosis of FH, their children should ideally be screened by the age of 10. 

Identifying FH at this age allows families to receive specialist dietary advice and for the child to be monitored by a paediatric lipid specialist. While most children do not start medication immediately, having a diagnosis ensures that they grow up with a heart-healthy lifestyle and that treatment can be discussed when they reach the appropriate age, typically between 8 and 10 years old. 

Genetic vs. Lipid Screening for Relatives 

The type of test a relative receives depends on whether a specific genetic mutation has been identified in the first family member diagnosed. 

If a mutation (such as in the LDLR gene) has been found in the index case, all relatives are offered a targeted DNA blood test. This is the most accurate method because it provides a definitive ‘yes’ or ‘no’ regardless of the person’s current cholesterol level. If no specific mutation was found in the first family member, relatives are screened using a full lipid profile, and their results are compared against age-specific and gender-specific cholesterol charts to determine the likelihood of FH. 

Causes and Triggers for Expanding the Search 

While the primary cause for screening is the initial diagnosis of a relative, certain triggers may prompt a more urgent or expanded search within a family tree. 

• Premature Cardiac Events: If a relative suffers a heart attack or stroke under the age of 60, it triggers an immediate review of the entire family’s lipid status. 

• Positive Genetic Result: Every time a new relative tests positive for the FH gene, it opens a new ‘cascade’ of testing for their own children and siblings. 

• Physical Signs: If a family member notices yellow lumps on their knuckles or a white ring around their eye (corneal arcus), this acts as a clinical trigger for everyone in that biological line to be checked. 

Differentiation: Index Case vs. Relative Screening 

It is important to differentiate between the criteria used to find the first person in a family (the index case) and the criteria used to screen their relatives. 

Feature	Index Case Screening	Relative (Cascade) Screening
Triggers	High cholesterol (>7.5) or early heart attack.	A relative being diagnosed with FH.
Primary Goal	To identify a new family with the condition.	To find at-risk members of a known family.
Testing Tool	Simon Broome or DLCN scores.	Targeted DNA test or lipid charts.
Urgency	Based on clinical symptoms or routine check.	Immediate referral once a mutation is known.

To Summarise (H3) 

Relatives should be screened for FH as soon as a biological family member is diagnosed. This cascade testing starts with first-degree relatives, who have a 50% chance of having the condition. Children should ideally be tested by the age of 10 to ensure early protection. By identifying affected relatives through genetic or lipid testing, the NHS can provide preventative care that dramatically reduces the risk of early heart disease and stroke. 

If you experience sudden, severe chest pain, shortness of breath, or sudden weakness on one side of your body, call 999 immediately. 

You may find our free BMI Calculator helpful for monitoring your overall health, as weight management is a supportive factor in managing cardiovascular risk. 

Authority Snapshot (H3) 

Dr. Rebecca Fernandez is a UK-trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, and emergency care. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive care across inpatient and outpatient settings. This article provides evidence-based information aligned with the 2026 clinical standards from the NHS and the British Heart Foundation regarding family screening for FH.