Estimating the prevalence of heterozygous familial hypercholesterolaemia: a systematic review and meta-analysis

How do the experiences and beliefs of adults and children with heterozygous familial hypercholesterolaemia influence their adherence to treatment? A systematic review of qualitative evidence protocol

BACKGROUND

Heterozygous familial hypercholesterolaemia (FH) is a genetic disorder characterised by elevated levels of low density lipoprotein (LDL) cholesterol from birth, estimated to affect 1 in 250 of the UK population. Left untreated, FH substantially increases an individual's risk of premature coronary heart disease (CHD) and associated mortality. This risk can be minimised with timely diagnosis and successful treatment with medication and lifestyle changes, as advocated in national and international guidelines. Despite these recommendations, the limited research available suggests adherence to treatment may be sub-optimal. This review will identify and synthesise the available qualitative research regarding the experiences and beliefs of adults and children with FH in relation to their condition and its treatment, and the influence of these upon treatment adherence.

METHODS

The following electronic databases will be searched from their inception: Cochrane library, MEDLINE, Embase, PsycINFO (via OVID) and CINAHL. Studies available in English and reporting primary qualitative data will be included. Database searching will be supplemented with searches in relevant specialist websites. The references of identified papers will also be hand searched. Two reviewers will independently screen titles and abstracts of identified studies, with full texts of potentially relevant papers retrieved for review against pre-defined inclusion and exclusion criteria. The Critical Appraisal Skills Programme (CASP) Qualitative Research checklist will be used to assess quality of the included studies, and the results will be taken into consideration when reporting the findings. A data extraction tool will be created for use in this review to extract study findings relevant to the review questions. A thematic synthesis approach will be taken to analyse the results.

DISCUSSION

Adherence to treatment recommendations is crucial for the successful management of FH and subsequent decrease in risk of CHD later in life. Common identified themes could provide an understanding of the beliefs and experiences which influence adherence to treatment recommendations and provide an insight into perceived barriers and facilitators. The findings are intended to be used in the development of future interventions or guidelines regarding treatment of children and adults with FH.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42018085946.

Estimation of the prevalence of cholesteryl ester storage disorder in a cohort of patients with clinical features of familial hypercholesterolaemia

BACKGROUND AND AIM

Familial hypercholesterolaemia is caused by variants in the low-density lipoprotein cholesterol metabolic pathway involving LDLR, APOB and PCSK9 genes. A national genetic testing service in Wales, UK has observed that no familial hypercholesterolaemia variant is found in almost 80% patients with the familial hypercholesterolaemia phenotype. It has recently been suggested that some adult patients with a familial hypercholesterolaemia phenotype may have cholesteryl ester storage disease which can also present as a mixed hyperlipidaemia. The commonest genetic cause of cholesteryl ester storage disease is an exon 8 splice junction variant in the LIPA gene (rs116928232, c.894G>A; E8SJM) previously found to have an allele frequency of 0.0011 (1 in 450 individuals) in a large European population. This study investigated the prevalence of the E8SJM in patients with a familial hypercholesterolaemia phenotype in Wales, UK.

METHOD

A total of 1203 patients with a clinical suspicion of familial hypercholesterolaemia but no familial hypercholesterolaemia variant were invited to participate. Of these, 668 patients provided informed written consent. Stored DNA samples from 663 patients were genotyped for the E8SJM variant.

RESULTS

Three heterozygotes were identified (allele frequency 0.0023). Whole gene sequencing of the LIPA gene was undertaken in these three individuals, but no other variants were found. Therefore, there were no cholesteryl ester storage disease patients (homozygote or compound heterozygote) identified in this cohort.

CONCLUSION

The allele frequency 0.0023 (1 in 221 individuals) for the E8SJM variant was more prevalent in this cohort than in a European population study; however, no cholesteryl ester storage disease homozygotes were identified. We found no evidence to support routine testing for cholesteryl ester storage disease in adult patients with a familial hypercholesterolaemia phenotype.

Predicting cardiovascular disease in familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia is a frequent genetic disease associated with a high lifetime risk of cardiovascular disease (CVD). Statins are the cornerstone of treatment of familial hypercholesterolemia; however, with the advent of novel LDL-cholesterol lowering therapies, it has become necessary to identify familial hypercholesterolemia subjects presenting a significant residual CVD risk. The aim of this review is to provide an update on the recent literature concerning cardiovascular risk stratification in familial hypercholesterolemia.

RECENT FINDINGS

Recently, several clinical and genetic factors have been shown to be independent predictors of CVD in familial hypercholesterolemia. These include clinical scores such as the Montreal-FH-SCORE, novel protein biomarkers, carotid plaque score and genetic predictors such as genetic risk scores as well as single-nucleotide polymorphisms.

SUMMARY

Although there has been recent progress in cardiovascular risk stratification in familial hypercholesterolemia, there is still a need to further refine our knowledge concerning phenotype modifiers in this disease. Indeed, current known predictors do not explain the entirety of cardiovascular risk. More precise individual risk stratification in familial hypercholesterolemia could help to better tailor the proper therapy for each patient.

Lipid and lipoprotein parameters for detection of familial hypercholesterolemia in childhood. The DECOPIN Project

BACKGROUND

Familial hypercholesterolaemia (FH) in children is under-detected and is difficult to diagnose in clinical practice. The aim of this study was to evaluate clinical, biochemical and vascular imaging variables in order to detect children and adolescents with FH.

METHODS

A total of 222 children aged 4-18 years old were recruited to participate in a project for the early detection of FH (The DECOPIN Project). They were distributed into 3groups: FH, if genetic study or clinical criteria were positive (n=91); Polygenic hypercholesterolaemia (PH) if LDL-Cholesterol >135mg/dL without FH criteria (n=23), and Control group (CG) if LDL-C <135mg/dL (n=108). Data were collected from family history, anthropometric data, and clinical variables. The usual biochemical parameters, including a complete lipid profile were analysed. The carotid intima-media thickness (cIMT) and thickness of Achilles tendons were determined using ultrasound in all participants.

RESULTS

A total of 91 children had a diagnosis of FH, 23 with PH, and 108 with CG. Children with FH had higher concentrations of total cholesterol, LDL-C, ApoB/ApoA1 ratio, and cholesterol-year score, than the other groups. HDL-C was lower in the FH group than in the CG. Thickness of the Achilles tendon and cIMT did not show any differences between groups, although a greater cIMT trend was observed in the FH group. ApoB/ApoA1 ratio >0.82 was the parameter with the highest sensitivity and specificity to predict the presence of mutation in children with FH.

CONCLUSIONS

Although LDL-C is the main biochemical parameter used to define FH, the ApoB/ApoA1 ratio (>0.82) may be a useful tool to identify children with FH and a positive mutation.

Universal screening at age 1-2 years as an adjunct to cascade testing for familial hypercholesterolaemia in the UK: A cost-utility analysis

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) is widely underdiagnosed. Cascade testing (CT) of relatives has been shown to be feasible, acceptable and cost-effective in the UK, but requires a supply of index cases. Feasibility of universal screening (US) at age 1-2 years was recently demonstrated. We examined whether this would be a cost-effective adjunct to CT in the UK, given the current and plausible future undiagnosed FH prevalence.

METHODS

Seven cholesterol and/or mutation-based US ± reverse cascade testing (RCT) alternatives were compared with no US in an incremental analysis with a healthcare perspective. A decision model was used to estimate costs and outcomes for cohorts exposed to the US component of each strategy. RCT case ascertainment was modelled using recent UK CT data, and probabilistic Markov models estimated lifetime costs and health outcomes for the cohorts screened under each alternative. 1000 Monte Carlo simulations were run for each model, and average outcomes reported. Further uncertainty was explored deterministically. Threshold analysis investigated the association between undiagnosed FH prevalence and cost-effectiveness.

RESULTS

A strategy involving cholesterol screening followed by diagnostic genetic testing and RCT was the most cost-effective modelled (incremental cost-effectiveness ratio (ICER) versus no US £12,480/quality adjusted life year (QALY); probability of cost-effectiveness 96·8% at £20,000/QALY threshold). Cost-effectiveness was robust to both deterministic sensitivity analyses and threshold analyses that modelled ongoing case ascertainment at theoretical maximum levels.

CONCLUSIONS

These findings support implementation of universal cholesterol screening followed by diagnostic genetic testing and RCT for FH, under a UK conventional willingness-to-pay threshold.

Anxiety, depression, and health-related quality of life in heterozygous familial hypercholesterolemia: A systematic review and meta-analysis

BACKGROUND

Heterozygous familial hypercholesterolemia (FH) is a common genetic disease predisposing affected individuals to a high risk of cardiovascular disease. Yet, considerable uncertainty exists regarding its impact on psychosocial wellbeing.

OBJECTIVES

We performed a systematic review and meta-analysis of the association between FH and symptoms of anxiety and depression, and health-related quality of life (HRQL).

METHODS

We searched MEDLINE, EMBASE, Global Health, the Cochrane Library, PsycINFO, and PubMed for peer-reviewed literature published in English between January 1, 1990 and January 1, 2018. Quantitative and qualitative studies were eligible if they included patients with confirmed FH and evaluated its association with symptoms of anxiety or depression, or HRQL. We performed a narrative synthesis of studies, including thematic analysis of qualitative studies, and where data permitted, random-effects meta-analysis reporting standardized mean differences (SMD) and 95% confidence intervals.

RESULTS

We found 10 eligible studies measuring HRQL, depression and anxiety. Random-effects meta-analysis of 4 (n = 4293) and 5 studies (n = 5098), respectively, showed that patients with FH had slightly lower symptoms of anxiety (SMD: -0.29 [95% CI: -0.53, -0.04]) and mental HRQL (SMD: -0.10 [95% -0.20, -0.00]) relative to general population controls. No significant differences existed in depressive symptoms (SMD: 0.04 [95% CI: -0.12, 0.19]) or physical HRQL scores (SMD: 0.02 [95% CI: -0.09, 0.12]).

CONCLUSIONS

Our systematic review suggests that patients with FH may report small but measurable differences in anxiety symptoms and mental HRQL.

Familial hypercholesterolemia with extensive coronary artery disease and tuberous and tendinous xanthomas: A case report and mutation analysis

This is a case report of a 38-year-old Syrian refugee male with early-onset extensive atherosclerosis. The physical and laboratory examination were remarkable with severe xanthomas in the upper and lower extremities and with low-density lipoprotein cholesterol (LDL-C) 417 mg/dL, total cholesterol 495 mg/dL, high-density lipoprotein cholesterol 30 mg/dL, and triglycerides 242 mg/dL. LDL-C level responded poorly to the high-dose statin treatment. The genetic analysis indicated that the patient had a large homozygous deletion in LDL receptor gene including the exons 7-14. A 12-kb deletion had occurred between the 2 Alu repetitive sequences that were oriented in opposite directions, one in intron 6 and the other in intron 14. This deletion eliminated exons 7-14, which exactly corresponded to the entire exon sequence coding the epidermal growth factor precursor homology domain. This deletion in LDL receptor was previously reported. This rare case of homozygous familial hypercholesterolemia presenting with multiple large and widely distributed xanthomas implicates the need for novel treatment options in familial hypercholesterolemia patients. The case is a Syrian refugee and emphasizes the urgent need to address orphan disease in refugee populations throughout the world.

Simplified Canadian Definition for Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal codominant lipoprotein disorder characterized by elevated low-density lipoprotein cholesterol (LDL-C) and high risk of premature atherosclerotic cardiovascular disease. Definitions for FH rely on complex algorithms that are on the basis of levels of total or LDL-C, clinical features, family history, and DNA analysis that are often difficult to obtain. We propose a novel simplified definition for FH. Definite FH includes: (1) elevated LDL-C (≥ 8.50 mmol/L); or (2) LDL-C ≥ 5.0 mmol/L (for age 40 years or older; ≥ 4.0 mmol/L if age younger than 18 years; and ≥ 4.5 mmol/L if age is between 18 and 39 years) when associated with at least 1 of: (1) tendon xanthomas; or (2) causal DNA mutation in the LDLR, APOB, or PCSK9 genes in the proband or first-degree relative. Probable FH is defined as subjects with an elevated LDL-C (≥ 5.0 mmol/L) and the presence of premature atherosclerotic cardiovascular disease in the patient or a first-degree relative or an elevated LDL-C in a first-degree relative. LDL-C cut points were determined from a large database comprising > 3.3 million subjects. To compare the proposed definition with currently used algorithms (ie, the Simon Broome Register and Dutch Lipid Clinic Network), we performed concordance analyses in 5987 individuals from Canada. The new FH definition showed very good agreement compared with the Simon Broome Register and Dutch Lipid Clinic Network criteria (κ = 0.969 and 0.966, respectively). In conclusion, the proposed FH definition has diagnostic performance comparable to existing criteria, but adapted to the Canadian population, and will facilitate the diagnosis of FH patients.

Familial hypercholesterolemia: experience from the French-Canadian population

PURPOSE OF REVIEW

There has recently been renewed interest in the study of the various facets of familial hypercholesterolemia, a severe monogenic disease associated with elevated LDL-cholesterol and premature cardiovascular disease (CVD). In the present review, novel data presenting the frequency of familial hypercholesterolemia as well as factors modulating the cardiovascular risk in familial hypercholesterolemia will be discussed.

RECENT FINDINGS

Recent studies have showed that familial hypercholesterolemia is much more prevalent than initially thought. Classically, it was estimated that familial hypercholesterolemia affected one in 500 people worldwide, but a recent large-scale meta-analysis has shown a prevalence closer to one in 250. In the French-Canadian population, this disease is even more frequent reaching one in 81 in certain regions of the Province of Quebec. Several novel studies in the French-Canadian population have shown that the clinical outcomes in familial hypercholesterolemia seem to be greatly influenced by risk factors other than LDL-cholesterol. Also, scores to predict CVD in familial hypercholesterolemia have been recently proposed.

SUMMARY

Familial hypercholesterolemia is more frequent than initially thought and the phenotype of this disease can be variable. Indeed, both clinical and genetic variables can modulate the CVD risk in this population.

Population specific genetic heterogeneity of familial hypercholesterolemia in South Africa

PURPOSE OF REVIEW

To describe the prevalence and population-specific genetic heterogeneity of familial hypercholesterolemia in South Africa.

RECENT FINDINGS

This review highlights the paucity of data on familial hypercholesterolemia in South Africa, and the urgent need to uncover the mutation profiles in lipid-associated genes, causing an increase in LDL-cholesterol in the different ethnic groups. Case reports and small studies have shown that familial hypercholesterolemia, although apparently uncommon, is present in black Africans.

SUMMARY

Local founder effects have led to an increased prevalence of familial hypercholesterolemia in several South African populations: Afrikaner founder mutations (c.681 C>G, c.1285 G>A, c.523 G>A), Ashkenazi founder mutation (c.654_656del) and possible Indian founder mutation (c.2054 C>T). Preliminary data in black Africans with elevated LDL-cholesterol identified a possible common mutation, c.137_142del. The South African multiethnic society and well described founder effects emphasize the need for differential approaches to diagnosis and management of familial hypercholesterolemia. Studies involving larger cohorts and inclusive of different ethnicities are paramount to establishing an accurate prevalence of familial hypercholesterolemia in black Africans, not only in South Africa but in the Sub-Saharan African region. It is clear that the estimated world prevalence of one in 250 cannot be generally applied across African populations.

Imputation of Baseline LDL Cholesterol Concentration in Patients with Familial Hypercholesterolemia on Statins or Ezetimibe

BACKGROUND

Familial hypercholesterolemia (FH) is the most frequent genetic disorder seen clinically and is characterized by increased LDL cholesterol (LDL-C) (&gt;95th percentile), family history of increased LDL-C, premature atherosclerotic cardiovascular disease (ASCVD) in the patient or in first-degree relatives, presence of tendinous xanthomas or premature corneal arcus, or presence of a pathogenic mutation in the LDLR, PCSK9, or APOB genes. A diagnosis of FH has important clinical implications with respect to lifelong risk of ASCVD and requirement for intensive pharmacological therapy. The concentration of baseline LDL-C (untreated) is essential for the diagnosis of FH but is often not available because the individual is already on statin therapy.

METHODS

To validate a new algorithm to impute baseline LDL-C, we examined 1297 patients. The baseline LDL-C was compared with the imputed baseline obtained within 18 months of the initiation of therapy. We compared the percent reduction in LDL-C on treatment from baseline with the published percent reductions.

RESULTS

After eliminating individuals with missing data, nonstandard doses of statins, or medications other than statins or ezetimibe, we provide data on 951 patients. The mean ± SE baseline LDL-C was 243.0 (2.2) mg/dL [6.28 (0.06) mmol/L], and the mean ± SE imputed baseline LDL-C was 244.2 (2.6) mg/dL [6.31 (0.07) mmol/L] (P = 0.48). There was no difference in response according to the patient's sex or in percent reduction between observed and expected for individual doses or types of statin or ezetimibe.

CONCLUSIONS

We provide a validated estimation of baseline LDL-C for patients with FH that may help clinicians in making a diagnosis.

Familial Hypercholesterolaemia Diagnosis and Management

Familial hypercholesterolaemia is the most common monogenic disorder associated with premature coronary artery disease. Mutations are most frequently found in the LDL receptor gene. Clinical criteria can be used to make the diagnosis; however, genetic testing will confirm the disorder and is very useful for cascade screening. Early identification and adequate treatment can improve prognosis, reducing negative clinical cardiovascular outcomes. Patients with familial hypercholesterolaemia are considered at high cardiovascular risk and the treatment target is LDL cholesterol <2.6 mmol/l or at least a 50 % reduction in LDL cholesterol. Patients require intensive treatment with statins and ezetimibe and/or colesevelam. Recently, proprotein convertase subtilisin/kexin type 9 inhibitors have been approved for the management of familial hypercholesterolaemia on top of statins.