The importance of cascade genetic screening for diagnosing autosomal dominant hypercholesterolemia: Results from twenty years of a national screening program in Norway

Genetic testing for familial hypercholesterolemia in a Finnish cohort of patients with premature coronary artery disease and elevated LDL-C levels

Background

Based on Finnish LDLR-founder variations, the prevalence of familial hypercholesterolemia (FH) in Finland is estimated to be at least 1:600. Patients with FH have increased risk of premature coronary artery disease (CAD) and thus the prevalence of FH is expected to be higher in this subgroup.

Objective

To assess the prevalence of monogenic FH in a Finnish cohort of patients with premature CAD and elevated low-density lipoprotein cholesterol (LDL-C) levels.

Methods

Among 28,295 patients undergoing angiography at Heart Hospital at Tampere University Hospital between 2007 and 2017, we identified 162 patients diagnosed with premature CAD (men aged <55 years and women aged <60 years) and history of high LDL-C (≥5 mmol/L) levels without secondary causes of hypercholesterolemia. Clinical probability of FH was estimated, and genetic testing of FH was carried out in 80 patients with informed consent.

Results

Of the 80 patients with premature CAD and history of high LDL-C levels, 70% were men; the age at diagnosis of CAD for male and female patients was 48 and 53 years, respectively. In total, 58 (73%) patients had probable (n = 54) or definite (n = 4) FH based on Dutch Lipid Clinic Network criteria. A pathogenic variant of FH was found in five (6%) patients. Prevalence of the genetically verified FH was 1:16. The FH variant was found in 75% of patients with definite FH.

Conclusions

The prevalence of genetically verified FH was 1:16 among patients with premature CAD and elevated LDL-C level, which is 38 times higher than the estimated prevalence of 1:600 in the general Finnish population.

Cascade genetic counseling and testing in hereditary syndromes: inherited cardiovascular disease as a model: a narrative review

Inherited cardiovascular diseases cover the inherited cardiovascular disease familial hypercholesterolemia and inherited cardiac diseases, like inherited cardiomyopathies and inherited arrhythmia syndromes. Cascade genetic counseling and testing in inherited cardiovascular diseases have had three decades of academic attention. Inherited cardiovascular diseases affect around 1-2% of the population worldwide and cascade genetic counseling and testing are considered valuable since preventive measures and/or treatments are available. Cascade genetic counseling via a family-mediated approach leads to an uptake of genetic counseling and testing among at-risk relatives of around 40% one year after identification of the causal variant in the proband, with uptake remaining far from complete on the long-term. These findings align with uptake rates among relatives at-risk for other late onset medically actionable hereditary diseases, like hereditary cancer syndromes. Previous interventions to increase uptake have focused on optimizing the process of informing relatives through the proband and on contacting relatives directly. However, despite successful information dissemination to at-risk relatives, these approaches had little or no effect on uptake. The limited research into the barriers that impede at-risk relatives from seeking counseling has revealed knowledge, attitudinal, social and practical barriers but it remains unknown how these factors contribute to the decision-making process for seeking counseling in at-risk relatives. A significant effect on uptake of genetic testing has only been reached in the setting of familial hypercholesterolemia, where active information provision was accompanied by a reduction of health-system-related barriers. We propose that more research is needed on barriers -including health-system-related barriers- and how they hinder counseling and testing in at-risk relatives, so that uptake can be optimized by (adjusted) interventions.

Genetic Screening-Emerging Issues

In many countries, some form of genetic screening is offered to all or part of the population, either in the form of well-organized screening programs or in a less formalized way. Screening can be offered at different phases of life, such as preconception, prenatal, neonatal and later in life. Screening should only be offered if the advantages outweigh the disadvantages. Technical innovations in testing and treatment are driving changes in the field of prenatal and neonatal screening, where many jurisdictions have organized population-based screening programs. As a result, a greater number and wider range of conditions are being added to the programs, which can benefit couples' reproductive autonomy (preconception and prenatal screening) and improve early diagnosis to prevent irreversible health damage in children (neonatal screening) and in adults (cancer and cascade screening). While many developments in screening are technology-driven, citizens may also express a demand for innovation in screening, as was the case with non-invasive prenatal testing. Relatively new emerging issues for genetic screening, especially if testing is performed using DNA sequencing, relate to organization, data storage and interpretation, benefit-harm ratio and distributive justice, information provision and follow-up, all connected to acceptability in current healthcare systems.

International Atherosclerosis Society guidance for implementing best practice in the care of familial hypercholesterolaemia

This contemporary, international, evidence-informed guidance aims to achieve the greatest good for the greatest number of people with familial hypercholesterolaemia (FH) across different countries. FH, a family of monogenic defects in the hepatic LDL clearance pathway, is a preventable cause of premature coronary artery disease and death. Worldwide, 35 million people have FH, but most remain undiagnosed or undertreated. Current FH care is guided by a useful and diverse group of evidence-based guidelines, with some primarily directed at cholesterol management and some that are country-specific. However, none of these guidelines provides a comprehensive overview of FH care that includes both the lifelong components of clinical practice and strategies for implementation. Therefore, a group of international experts systematically developed this guidance to compile clinical strategies from existing evidence-based guidelines for the detection (screening, diagnosis, genetic testing and counselling) and management (risk stratification, treatment of adults or children with heterozygous or homozygous FH, therapy during pregnancy and use of apheresis) of patients with FH, update evidence-informed clinical recommendations, and develop and integrate consensus-based implementation strategies at the patient, provider and health-care system levels, with the aim of maximizing the potential benefit for at-risk patients and their families worldwide.

Cascade screening for familial hypercholesterolemia should be organized at a national level

PURPOSE OF REVIEW

Patients with familial hypercholesterolemia (FH) have a markedly increased risk of premature cardiovascular disease. However, there are effective lipid-lowering therapies available to reduce the risk of cardiovascular disease. This makes it important to diagnose these patients. The most cost-effective strategy to diagnose patients with FH is to perform cascade screening. However, cascade screening as part of ordinary healthcare has not been very successful. Thus, there is a need to implement more efficient cascade screening strategies.

RECENT FINDINGS

Cascade screening for FH should be organized at a national level and should be run by dedicated health personnel such as genetic counsellors. As part of a national organization a national registry of patients with FH needs to be established. Moreover, for cascade screening to be effective, diagnosis of FH must be based on identifying the underlying mutation. There should preferably only be one genetics centre in each country for diagnosing FH, and this genetics centre should be an integrated part of the national cascade screening program.

SUMMARY

Cascade screening for FH is very effective and should be organized at a national level. Even a modest national cascade screening program can result in a large number of patients being identified.