Simon Broome diagnostic criteria for familial hypercholesterolemia (FH)

UK register-based criteria: cholesterol thresholds depend on whether the patient is under 16 years. Definite FH is supported by a documented FH-causing mutation or by marked hypercholesterolemia with tendon xanthoma in the patient or a first- or second-degree relative. Possible FH uses the same lipid entry criteria plus defined family-history features.

Lipid thresholds (either TC or LDL-C can satisfy the entry criterion):

Adult (≥16 y): TC ≥ 290 mg/dL or LDL-C ≥ 190 mg/dL
Child (<16 y): TC ≥ 260 mg/dL or LDL-C ≥ 155 mg/dL

Age (years)

Lipid unit

Total cholesterol (optional if LDL-C entered)

LDL-C (optional if TC entered)

Definite FH

Documented pathogenic / likely pathogenic mutation in LDLR, APOB, or PCSK9 (or equivalent national laboratory reporting)

Tendon xanthomas (with qualifying lipids above):

Tendon xanthoma in the patientTendon xanthoma in a first-degree relativeTendon xanthoma in a second-degree relative

Possible FH (family history — only applies when lipid criterion is met)

Myocardial infarction in a first-degree relative before age 60 yearsMyocardial infarction in a second-degree relative before age 50 yearsFirst- or second-degree adult relative with total cholesterol >7.5 mmol/L (~290 mg/dL)Sibling under 16 years with total cholesterol >6.7 mmol/L (~260 mg/dL)

Disclaimer: This tool encodes widely published Simon Broome register criteria for education and workflow support. It is not medical advice and does not replace examination, genetics, or national guidance (for example NICE familial hypercholesterolemia pathways).

Simon Broome criteria — explained

Background

The Simon Broome criteria come from the Simon Broome Familial Hypercholesterolemia Register in the United Kingdom and remain a standard way to classify adults and children into definite or possible familial hypercholesterolemia (FH) for referral, registry, and cascade-testing workflows. They are summarized in many evidence reviews (for example AHRQ/NCBI Table 2) and in UK service guidance.

Reference: Scientific Steering Committee on behalf of the Simon Broome Register Group. Risk of fatal coronary heart disease in familial hypercholesterolaemia. BMJ. 1991;303(6807):893–6.

Step 1 — Lipid entry criterion

The patient must have total cholesterol and/or LDL-C at or above the age-specific cut-off. Meeting either lipid measure is enough.

Group	Total cholesterol	LDL-C
Adult (≥16 years)	≥290 mg/dL (≥7.5 mmol/L)	≥190 mg/dL (≥4.9 mmol/L)
Child (<16 years)	≥260 mg/dL (≥6.7 mmol/L)	≥155 mg/dL (≥4.0 mmol/L)

Conversion in this app uses 1 mmol/L ≈ 38.67 mg/dL for cholesterol. Minor rounding may differ from local laboratory reporting conventions.

Step 2 — Definite FH

Definite FH is supported if either:

DNA evidence of an FH-causing abnormality (for example LDLR, familial defective APOB, PCSK9), or
The lipid entry criterion is met and there are tendon xanthomas in the patient or in a first- or second-degree relative.

Tendon xanthomas are distinct from xanthelasma or corneal arcus alone; those findings may be clinically important but are not the tendon xanthoma criterion in the classic Simon Broome scheme.

Step 3 — Possible FH

If the patient is not classified as definite, but the lipid entry criterion is met, they may meet possible FH when at least one of the following applies:

Premature myocardial infarction in a first-degree relative before age 60 years, or in a second-degree relative before age 50 years.
Marked hypercholesterolemia in a relative: adult first- or second-degree relative with total cholesterol above about 7.5 mmol/L (290 mg/dL), or a sibling under 16 years with total cholesterol above about 6.7 mmol/L (260 mg/dL).

How this calculator maps inputs

Age chooses pediatric versus adult lipid thresholds; relationships and ages for MI or sibling age are not verified beyond your checkbox answers.
Definite FH overrides possible FH when tendon xanthoma with qualifying lipids or documented mutation is selected.
If lipids meet the threshold but no definite features and no possible family-history box is checked, the tool reports that the lipid criterion alone is insufficient for definite or possible Simon Broome classification.

Overview

The Simon Broome criteria are a set of clinical diagnostic rules developed from the United Kingdom’s Simon Broome Familial Hypercholesterolemia Register. They are used to stratify individuals into definite and possible familial hypercholesterolemia (FH) for referral, epidemiology, and cascade screening. FH is an autosomal dominant disorder of LDL clearance dominated by pathogenic variants affecting the LDL receptor pathway (classically LDLR, with important contributions from APOB and PCSK9). Because untreated FH confers a high lifetime risk of premature atherosclerotic cardiovascular disease, consistent case identification matters for patients and relatives.

Simon Broome classification should be read as a structured clinical framework, not a replacement for specialist assessment. In practice, results are combined with physical examination (with particular attention to tendon findings), longitudinal lipid measurements, corneal and cutaneous signs, imaging when indicated, and confirmatory molecular testing as available.

Why a dedicated UK criteria set exists

Several international schemes address FH (for example Dutch lipid clinic criteria, US MEDPED thresholds, and later genotype-first approaches). The Simon Broome criteria remain widely cited because they align with UK service design and provide explicit cholesterol cut-points tied to age, together with phenotype and family-history clauses that reflect how FH presented in early registry cohorts. They also cleanly separate a higher-certainty “definite” band (anchored by tendon xanthomata or DNA) from a broader “possible” band defined by extreme lipids plus selected cardiovascular and family lipid patterns.

Core lipid entry thresholds

Most Simon Broome pathways require the patient to meet an age-specific abnormality of cholesterolemia before upper classifications are considered. In typical tabulations, the entry criterion is met if either total cholesterol or LDL cholesterol reaches the corresponding cut-off. Thresholds are stricter for children than for the adult pattern because age-specific lipid distributions differ and pediatric recognition drives earlier preventive therapy.

Age group	Total cholesterol (approx.)	LDL cholesterol (approx.)
Adults (16 years and older)	≥ 7.5 mmol/L (≥ 290 mg/dL)	≥ 4.9 mmol/L (≥ 190 mg/dL)
Children (under 16 years)	≥ 6.7 mmol/L (≥ 260 mg/dL)	≥ 4.0 mmol/L (≥ 155 mg/dL)

Laboratories may report LDL-C as calculated (for example Friedewald-type estimates when triglycerides are not elevated) or as direct measurement; whichever value is clinically trusted should be used for comparison to the LDL cut-off. If only total cholesterol is available, the criterion can still be satisfied through the total cholesterol arm alone.

Definite familial hypercholesterolemia

Definite FH under Simon Broome thinking corresponds to situations where either the phenotype is highly specific or the genetic substrate is demonstrated.

DNA-based definite FH

Identification of a pathogenic or likely pathogenic variant in a gene known to cause autosomal dominant FH (most commonly LDLR, with APOB and PCSK9 representing other well-recognized loci) generally places an individual in a definite category when reporting follows national laboratory standards. Variant interpretation evolves with databases and familial segregation data, so clinical reporting language (for example “pathogenic” versus “variant of uncertain significance”) materially affects whether this arm is met.

Phenotype-based definite FH: tendon xanthomata with qualifying lipids

Eruptive or tuberous xanthomas related to extreme hypertriglyceridemia are not the target finding. Tendon xanthomata classically involve sites such as the Achilles tendons and extensor tendons of the hands; they reflect chronic cholesterol deposition in tendon structures and are relatively specific for severe primary LDL-elevation disorders in the right clinical context.

For definite classification on phenotype grounds, Simon Broome logic expects qualifying hypercholesterolemia and tendon xanthomata in the patient or in a first- or second-degree relative. This family-level allowance matters because an affected relative may carry the same dominant allele and manifest characteristic deposits even when index lipid documentation is incomplete.

Possible familial hypercholesterolemia

When an individual is not definite by genetics or tendon xanthomata, but still has lipids meeting the Simon Broome entry thresholds, the criteria define a possible category using family history features that increase pre-test probability for autosomal dominant inheritance of marked LDL elevation.

Premature myocardial infarction in relatives

The scheme uses discrete age cut-offs tied to relationship distance:

First-degree relative with myocardial infarction before age 60 years, or
Second-degree relative with myocardial infarction before age 50 years.

These thresholds attempt to capture premature coronary disease patterns compatible with familial clustering. Clinical documentation of MI (and careful distinction from other acute coronary syndromes) is important when histories are obtained retrospectively.

Markedly elevated cholesterol in relatives

Possible FH can also be supported when there is evidence of severe hypercholesterolemia in close relatives, including:

Adult first- or second-degree relative with total cholesterol above about 7.5 mmol/L (290 mg/dL), or
Sibling under 16 years with total cholesterol above about 6.7 mmol/L (260 mg/dL).

The sibling-specific pediatric threshold mirrors the idea that an affected brother or sister may reveal the family genotype early, even before adult relatives have been systematically screened.

How clinicians typically use the output bands

Definite FH usually triggers accelerated pathways: specialist lipid evaluation, high-intensity LDL lowering, imaging discussions guided by age and risk, family screening, and formal molecular testing or confirmation per local laboratory policy. The goal is not only to treat the index patient but to identify undiagnosed relatives who may be normolipidemic at a single time point yet still carry risk.

Possible FH commonly warrants similar escalation even before a variant is found, because the pre-test probability remains substantial when lipids are extreme and family patterns fit. Many systems treat “possible” as sufficient for referral and cascade coordination, recognizing that genetic testing may reclassify certainty over time.

When cholesterol is elevated but no additional Simon Broome feature is present, clinicians still address cardiovascular risk and evaluate for secondary causes, polygenic hypercholesterolemia, and other genetic lipid disorders; the absence of a Simon Broome upper band does not equate to “no concern.”

Relationship to examination findings not used as tendon criteria

Xanthelasma and corneal arcus are frequently discussed in FH clinics. They may accompany severe hypercholesterolemia but are not substitutes for tendon xanthomata within the classical Simon Broome definite phenotype arm. Likewise, the criteria do not replace tools that quantify overall short-term cardiovascular risk in the general population; FH care emphasizes lifetime LDL burden and early prevention rather than a single 10-year risk estimate alone.

Use with this calculator

Electronic worksheets should be checked against locally endorsed threshold units, age rules, and documentation standards for genetic results. Family histories should be verified where feasible, and borderline lipid values may merit confirmatory fasting profiles or repeat testing according to laboratory quality goals.

CalcMD.

Simon Broome Diagnostic Criteria for Familial Hypercholesterolemia (FH)

In-depth guide to UK Simon Broome FH criteria: definite vs possible classification, adult and pediatric cholesterol thresholds, tendon xanthomata, DNA findings, and family-history features for referral and cascade screening.