A review on the diagnosis, natural history, and treatment of familial hypercholesterolaemia

LDLR-Gene therapy for familial hypercholesterolaemia: problems, progress, and perspectives

Coronary artery diseases (CAD) inflict a heavy economical and social burden on most populations and contribute significantly to their morbidity and mortality rates. Low-density lipoprotein receptor (LDLR) associated familial hypercholesterolemia (FH) is the most frequent Mendelian disorder and is a major risk factor for the development of CAD. To date there is no cure for FH. The primary goal of clinical management is to control hypercholesterolaemia in order to decrease the risk of atherosclerosis and to prevent CAD. Permanent phenotypic correction with single administration of a gene therapeutic vector is a goal still needing to be achieved. The first ex vivo clinical trial of gene therapy in FH was conducted nearly 18 years ago. Patients who had inherited LDLR gene mutations were subjected to an aggressive surgical intervention involving partial hepatectomy to obtain the patient's own hepatocytes for ex vivo gene transfer with a replication deficient LDLR-retroviral vector. After successful re-infusion of transduced cells through a catheter placed in the inferior mesenteric vein at the time of liver resection, only low-level expression of the transferred LDLR gene was observed in the five patients enrolled in the trial. In contrast, full reversal of hypercholesterolaemia was later demonstrated in in vivo preclinical studies using LDLR-adenovirus mediated gene transfer. However, the high efficiency of cell division independent gene transfer by adenovirus vectors is limited by their short-term persistence due to episomal maintenance and the cytotoxicity of these highly immunogenic viruses. Novel long-term persisting vectors derived from adeno-associated viruses and lentiviruses, are now available and investigations are underway to determine their safety and efficiency in preparation for clinical application for a variety of diseases. Several novel non-viral based therapies have also been developed recently to lower LDL-C serum levels in FH patients. This article reviews the progress made in the 18 years since the first clinical trial for gene therapy of FH, with emphasis on the development, design, performance and limitations of viral based gene transfer vectors used in studies to ameliorate the effects of LDLR deficiency.

A double heterozygote for familial hypercholesterolaemia and familial defective apolipoprotein B-100

Autosomal dominant hypercholesterolaemia is genetically heterogeneous, but most commonly (approximately 93%) caused by mutations in low-density lipoprotein receptor (LDLR), where the disease is known as familial hypercholesterolaemia (FH), or apolipoprotein B-100 (APOB) (approximately 5.5%), where the disease is known as familial defective APOB (FDB), while in approximately 2% of patients the mutation is in the proprotein convertase subtilisin/kexin type 9 gene. Homozygous FH having inheritance of two LDLR mutations is a rare but recognized syndrome associated with an extreme hypercholesterolaemia and early-onset coronary artery disease. We present a 15-year-old girl with untreated total cholesterol levels of 8.8 mmol/L who was heterozygous for both the LDLR p.Leu479Pro and APOB p.Arg3527Gln mutation. Cascade testing confirmed the paternal origin of the LDLR mutation and revealed a maternal diagnosis of FDB. This case provides further evidence that the combined effect of an LDLR and an APOB mutation give rise to a phenotype more severe than either mutation alone and is more severe than homozygous FDB, but less severe than homozygous FH. It also highlights the need to consider the presence of additional mutations in families where relatives have varying phenotypes.

Apolipoprotein B synthesis inhibition: results from clinical trials

PURPOSE OF REVIEW

Mipomersen is a second-generation antisense oligonucleotide developed to inhibit the synthesis of apolipoprotein B-100 in the liver. In this review we will summarize the results of recent preclinical and clinical studies addressing safety and low-density lipoprotein-cholesterol (LDL-c) lowering efficacy of this new compound.

RECENT FINDINGS

In phase 3 clinical trials, mipomersen has been shown to significantly reduce LDL-c in patients with homozygous and heterozygous familial hypercholesterolemia on maximally tolerated lipid-lowering therapy. Injection site reactions, flu-like symptoms and increases in liver transaminases were the main adverse events. A recent safety study, designed to investigate the effects of mipomersen on intrahepatic triglyceride content, failed to show evidence of clinically relevant hepatic steatosis after 13 weeks of treatment.

SUMMARY

Mipomersen is a new agent to lower LDL-c in patients at increased risk of cardiovascular disease and/or intolerant to statins. Whereas safety concerns have focused on hepatic fat accumulation, to date no evidence of clinically relevant increases of intrahepatic triglyceride content are reported. Ongoing and future studies are eagerly awaited to assess the impact of mipomersen on hepatic triglyceride content after prolonged exposure.

Genomic characterization of large rearrangements of the LDLR gene in Czech patients with familial hypercholesterolemia

Background

Mutations in the LDLR gene are the most frequent cause of Familial hypercholesterolemia, an autosomal dominant disease characterised by elevated concentrations of LDL in blood plasma. In many populations, large genomic rearrangements account for approximately 10% of mutations in the LDLR gene.

Methods

DNA diagnostics of large genomic rearrangements was based on Multiple Ligation dependent Probe Amplification (MLPA). Subsequent analyses of deletion and duplication breakpoints were performed using long-range PCR, PCR, and DNA sequencing.

Results

In set of 1441 unrelated FH patients, large genomic rearrangements were found in 37 probands. Eight different types of rearrangements were detected, from them 6 types were novel, not described so far. In all rearrangements, we characterized their exact extent and breakpoint sequences.

Conclusions

Sequence analysis of deletion and duplication breakpoints indicates that intrachromatid non-allelic homologous recombination (NAHR) between Alu elements is involved in 6 events, while a non-homologous end joining (NHEJ) is implicated in 2 rearrangements. Our study thus describes for the first time NHEJ as a mechanism involved in genomic rearrangements in the LDLR gene.

Family history in public health practice: a genomic tool for disease prevention and health promotion

Family history is a risk factor for many chronic diseases, including cancer, cardiovascular disease, and diabetes. Professional guidelines usually include family history to assess health risk, initiate interventions, and motivate behavioral changes. The advantages of family history over other genomic tools include a lower cost, greater acceptability, and a reflection of shared genetic and environmental factors. However, the utility of family history in public health has been poorly explored. To establish family history as a public health tool, it needs to be evaluated within the ACCE framework (analytical validity; clinical validity; clinical utility; and ethical, legal, and social issues). Currently, private and public organizations are developing tools to collect standardized family histories of many diseases. Their goal is to create family history tools that have decision support capabilities and are compatible with electronic health records. These advances will help realize the potential of family history as a public health tool.

Effect of mipomersen, an apolipoprotein B synthesis inhibitor, on low-density lipoprotein cholesterol in patients with familial hypercholesterolemia

A randomized, double-blind, placebo-controlled, dose-escalation study was conducted to examine the efficacy and safety of mipomersen (ISIS 301012), an antisense inhibitor of apolipoprotein B, when added to conventional lipid-lowering therapy for patients with heterozygous familial hypercholesterolemia. A total of 44 patients were enrolled and were separated into 4 cohorts, with doses ranging from 50 to 300 mg (4:1 active treatment/placebo ratio). Patients received 8 doses subcutaneously during a 6-week treatment period. Patients assigned to the 300-mg dose continued for an additional 7 weeks with once-per-week dosing. The primary efficacy end point was the percentage of change from baseline to week 7 in low-density lipoprotein (LDL) cholesterol. Safety was assessed using the laboratory test results and according to the incidence, severity, and relation of adverse events to drug dose. Mipomersen produced significant reductions in LDL cholesterol and other atherogenic apolipoprotein B-containing lipoproteins. After 6 weeks of treatment, the LDL cholesterol level was reduced by 21% from baseline in the 200-mg/week dose group (p <0.05) and 34% from baseline in the 300-mg/week dose group (p <0.01), with a concomitant reduction in apolipoprotein B of 23% (p <0.05) and 33% (p <0.01), respectively. Injection site reactions were the most common adverse event. Elevations in liver transaminase levels (> or =3 times the upper limit of normal) occurred in 4 (11%) of 36 patients assigned to active treatment; 3 of these patients were in the highest dose group. In conclusion, mipomersen has an incremental LDL cholesterol lowering effect when added to conventional lipid-lowering therapy.

Mutation detection rate and spectrum in familial hypercholesterolaemia patients in the UK pilot cascade project

Cascade testing using DNA-mutation information is now recommended in the UK for patients with familial hypercholesterolaemia (FH). We compared the detection rate and mutation spectrum in FH patients with a clinical diagnosis of definite (DFH) and possible (PFH) FH. Six hundred and thirty-five probands from six UK centres were tested for 18 low-density lipoprotein receptor gene (LDLR) mutations, APOB p.Arg3527Gln and PCSK9 p.Asp374Tyr using a commercial amplification refractory mutation system (ARMS) kit. Samples with no mutation detected were screened in all exons by single strand conformation polymorphism analysis (SSCP)/denaturing high performance liquid chromatography electrophoresis (dHPLC)/direct-sequencing, followed by multiplex ligation-dependent probe amplification (MLPA) to detect deletions and duplications in LDLR.The detection rate was significantly higher in the 190 DFH patients compared to the 394 PFH patients (56.3% and 28.4%, p > 0.00001). Fifty-one patients had inadequate information to determine PFH/DFH status, and in this group the detection rate was similar to the PFH group (25.5%, p = 0.63 vs PFH). Overall, 232 patients had detected mutations (107 different; 6.9% not previously reported). The ARMS kit detected 100 (44%) and the MLPA kit 11 (4.7%). Twenty-eight (12%) of the patients had the APOB p.Arg3527Gln and four (1.7%) had the PCSK9 p.Asp374Tyr mutation. Of the 296 relatives tested from 100 families, a mutation was identified in 56.1%. In 31 patients of Indian/Asian origin 10 mutations (two previously unreported) were identified. The utility of the ARMS kit was confirmed, but sequencing is still required in a comprehensive diagnostic service for FH. Even in subjects with a low clinical suspicion of FH, and in those of Indian origin, mutation testing has an acceptable detection rate.

The effects of rosuvastatin on the serum cortisol, serum lipid, and serum mevalonic acid levels in the healthy Indian male population

In this open-label, balanced, randomized, placebo-controlled, parallel study, healthy male volunteers were randomly divided into two groups. Each group received either a single oral dose of rosuvastatin 20 mg or placebo. Estimations were done at predose on day 1 of dosing (baseline) and 24 h postdose after days 7 and 14. Serum cortisol and serum lipid levels were estimated using enzyme-linked immunosorbent assay kits and serum mevalonic acid (MVA) levels were measured using validated liquid chromatography-tandem mass spectrometry method. Rosuvastatin produced a statistically significant (P < 0.05) decrease in total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, and triglycerides. However, the increase in high-density lipoprotein cholesterol and decrease in cortisol and MVA were not statistically significant when compared to the placebo-treated group. The study showed that rosuvastatin at a dose of 20 mg/day for a period of 14 days was very potent as cholesterol-lowering agent, without any significant change in serum cortisol level in the healthy Indian male population.

Identification and management of familial hypercholesterolaemia: what does it mean to primary care?

Familial hypercholesterolaemia is one of the most common dominantly inherited disorders to be identified in primary care, leading to raised serum cholesterol evident from the first year of life. Around 1 in 500 people are affected by this condition, but less than 15% of these are currently attending lipid clinics, suggesting that the vast majority are unrecognised in general practice. The recently released National Institute for Health and Clinical Excellence evidence-based guideline on the identification and management of familial hypercholesterolaemia provides an opportunity to bridge this gap. Primary care has a role in systematic and opportunistic case finding, such as recognising the relevance of a family history of premature coronary heart disease and/or grossly elevated cholesterol. Although affected individuals need specialist care, GPs can reinforce the information provided by specialists and support cascade screening to other affected members of the extended family.

Heterozygous familial hypercholesterolaemia in childhood: cardiovascular risk prevention

Children with familial hypercholesterolaemia (FH) have severely increased low-density lipoprotein cholesterol (LDL-C) levels that strongly predispose to premature cardiovascular disease (CVD) later in life. Early identification makes it possible to start lipid-lowering therapy at young age to prevent CVD. The atherosclerotic process can be inhibited by potent lipid-lowering therapy. The cornerstone of lipid-lowering therapy is a healthy lifestyle, but most of the time this is insufficient to reach adequate LDL-C goals. Subsequently, pharmacological therapy is initiated with increasing frequency. In the past decade numerous studies have assessed the efficacy and safety of statins in children with FH. Those studies demonstrate that statins are well tolerated, safe and effective. Therefore, these agents have a pivotal role in the treatment of children with FH.

Pregnancy in women suffering from familial hypercholesterolemia: a harmful period for both mother and newborn?

PURPOSE OF REVIEW

The present review aims to highlight the consequences for mother and child of profound hypercholesterolemia during pregnancy of women with familial hypercholesterolemia.

RECENT FINDINGS

Familial hypercholesterolemia is increasingly diagnosed in younger patients due to the existence of screening programs and more widespread cholesterol testing. Increasing numbers of young female patients with familial hypercholesterolemia raise the issue of pregnancy and its consequences for the familial hypercholesterolemia patient herself but also for her offspring. When pregnancy is considered, lipid-lowering drugs are often discontinued because of the fear for teratogenic effects. The evidence for teratogenesis associated with statin use is scant and conflicting. On the other hand, several studies do suggest that pronounced hypercholesterolemia during pregnancy has adverse effects on both fetus and mother. In fact, human and animal studies reveal an enhanced tendency toward atherosclerosis in the offspring of women who suffer from hypercholesterolemia during pregnancy. In animal studies, some evidence exists that this can be reversed by treatment with lipid-lowering and antioxidative agents. Until today, however, no human studies exist that have evaluated efficacy or safety of lipid-lowering interventions in pregnant women with familial hypercholesterolemia.

SUMMARY

Altogether, the suggested relationship between severe hypercholesterolemia and enhanced atherosclerosis in offspring and possibly the mother warrants further confirmation and, consequently, studies that focus on therapeutic strategies that can safely lower cholesterol levels during pregnancy in these women.

Development of a high-resolution melting method for mutation detection in familial hypercholesterolaemia patients

Aims

Current screening methods, such as single strand conformational polymorphism (SSCP) and denaturing high performance liquid chromatography (dHPLC) that are used for detecting mutations in familial hypercholesterolaemia (FH) subjects are time consuming, costly and only 80–90% sensitive. Here we have tested high-resolution melt (HRM) analysis for mutation detection using the Rotor-Gene6000 realtime rotary analyser.

Methods and subjects

Polymerase chain reaction and melt conditions (HRM) for 23 fragments of the LDL-receptor gene, a region of exon 26 in the APOB gene (including p.R3527Q) and exon 7 of the PCSK9 gene (including p.D374Y) were optimized. Two double stranded DNA saturating dyes, LC-Green and Syto9, were compared for sensitivity. Eighty-two samples with known mutations were used as positive controls. Twenty-eight Greek FH heterozygous patients and two homozygous patients from the UK and Croatia were screened.

Results

HRM was able to identify all the positive control mutations tested, with similar results with either dye. Eight different variations were found in 17 of the 28 Greek FH patients for an overall detection rate of 61%: c.41delT (1), p.W165X (1), p.C173R (3), p.S286R (2), p.V429M (4), p.G549D (4), p.V613I (1), and a previously unreported mutation p.F694V (1) which is predicted to be FH-causing by functional algorithms. Mutations were found in both the homozygous patients; p.Q92X (Croatia) and p.Y489C (UK); both patients were homozygous for their respective mutations.

Conclusions

HRM is a sensitive, robust technique that could significantly reduce the time and cost of screening for mutations in a clinical setting.

Sex-associated effect of CETP and LPL polymorphisms on postprandial lipids in familial hypercholesterolaemia

Background

This study assessed the gender-specific influence of the cholesteryl ester transfer protein (TaqIB, I405V) and lipoprotein lipase (S447X) polymorphisms on the response to an oral fat tolerance test in heterozygotes for familial hypercholesterolaemia.

Methods

We selected and genotyped 80 men and postmenopausal women heterozygous for familial hypercholesterolaemia (main group) as well as 11 healthy control subjects. Patients were subgrouped based on their response to oral fat tolerance test. The oral fat tolerance test was defined as pathological when postprandial triglyceride concentration was higher than the highest triglyceride concentration observed in healthy subjects (220 mg/dl) at any time (2, 4, 6 or 8 h).

Results

In the pathological subgroup, men had significantly higher incremental area under the curve after oral fat tolerance test than postmenopausal women. Furthermore, multivariate analysis revealed a gender association of TaqIB and I405V influence on postprandial lipaemia in this subgroup.

Conclusion

In conclusion, it seems that gender and TaqIB polymorphism of the cholesteryl ester transfer protein gene were both associated with the distribution of triglyceride values after oral fat tolerance test, only in subjects with a pathological response to oral fat tolerance test. Specifically, men carrying the B2 allele of the TaqIB polymorphism showed a higher postprandial triglyceride peak and a delayed return to basal values compared with women carrying B2. However, further investigations in larger populations are required to replicate and confirm these findings.

Multiplex ligation-dependent probe amplification analysis to screen for deletions and duplications of the LDLR gene in patients with familial hypercholesterolaemia

The most common genetic defect in patients with autosomal dominant hypercholesterolaemia is a mutation of the low-density lipoprotein receptor (LDLR) gene. An estimate of the frequency of major rearrangements has been limited by the availability of an effective analytical method and testing of large cohorts. We present data from a cohort of 611 patients referred with suspected heterozygous familial hypercholesterolaemia (FH) from five UK lipid clinics, who were initially screened for point mutations in LDLR and the common APOB and PCSK9 mutations. The 377 cases in whom no mutation was found were then screened for large rearrangements by multiplex ligation-dependent probe amplification (MLPA) analysis. A rearrangement was identified in 19 patients. This represents 7.5% of the total detected mutations of the cohort. Of these, the majority of mutations (12/19) were deletions of more than one exon, two were duplications of more than one exon and five were single exon deletions that need interpreting with care. Five rearrangements (26%) are previously unreported. We conclude that MLPA analysis is a simple and rapid method for detecting large rearrangements and should be included in diagnostic genetic testing for FH.

Inherited metabolic disorders and cerebral infarction

The association of genetic factors and cerebral infarction (CI) has long been established. A positive family history alone is a recognized risk factor for CI and vascular events in general. However, there are certain inherited conditions that further increase the risk of stroke. These conditions are generally metabolic and mitochondrial genetic defects that have variable modes of inheritance. This article reviews major inherited metabolic disorders that predispose an individual to CI. Ten main conditions will be discussed: Fabry's disease, cerebrotendinous xanthomatosis, tangier disease, familial hypercholesterolemia, homocystinuria, methylmalonic acidemia, glutaric aciduria type I, propionic acidemia, ornithine transcarbamylase deficiency and mitochondrial encephalopathy, lactic acidosis and stroke-like phenomenon.

Efficacy of statins in familial hypercholesterolaemia: a long term cohort study

OBJECTIVE

To determine the efficacy of statin treatment on risk of coronary heart disease in patients with familial hypercholesterolaemia.

DESIGN

Cohort study with a mean follow-up of 8.5 years.

SETTING

27 outpatient lipid clinics.

SUBJECTS

2146 patients with familial hypercholesterolaemia without prevalent coronary heart disease before 1 January 1990.

MAIN OUTCOME MEASURES

Risk of coronary heart disease in treated and "untreated" (delay in starting statin treatment) patients compared with a Cox regression model in which statin use was a time dependent variable.

RESULTS

In January 1990, 413 (21%) of the patients had started statin treatment, and during follow-up another 1294 patients (66%) started after a mean delay of 4.3 years. Most patients received simvastatin (n=1167, 33 mg daily) or atorvastatin (n=211, 49 mg daily). We observed an overall risk reduction of 76% (hazard ratio 0.24 (95% confidence interval 0.18 to 0.30), P<0.001). In fact, the risk of myocardial infarction in these statin treated patients was not significantly greater than that in an age-matched sample from the general population (hazard ration 1.44 (0.80 to 2.60), P=0.23).

CONCLUSION

Lower statin doses than those currently advised reduced the risk of coronary heart disease to a greater extent than anticipated in patients with familial hypercholesterolaemia. With statin treatment, such patients no longer have a risk of myocardial infarction significantly different from that of the general population.

Comparison of genetic versus clinical diagnosis in familial hypercholesterolemia

Early diagnosis is important in familial hypercholesterolemia (FH), a highly atherogenic condition, but internationally agreed clinical diagnostic criteria are lacking. Genetic testing for low-density lipoprotein (LDL) receptor (LDLR) and apolipoprotein B (APOB) gene defects is the preferable diagnostic method, but the best phenotype indication to proceed with genetic diagnosis has not been established. The aim of this study was to assess the predictive and accuracy values of standard diagnostic criteria for detecting disease-causing mutations in 825 subjects with clinical FH aged > or =14 years from 3 lipid clinics in Spain. All subjects underwent thorough genetic testing for the detection of LDLR and APOB defects using the Lipochip platform. FH-causing mutations were detected in 459 subjects (55.6%). By logistic regression analysis, familial or personal history of tendon xanthoma (TX) and LDL cholesterol were strongly associated with genetic diagnosis (p <0.005, R(2) = 0.41). In subjects without familial or personal histories of TX, the diagnostic criteria for FH of the Make Early Diagnosis to Prevent Early Deaths (MEDPED) project, based on age-specific LDL cholesterol thresholds, showed sensitivity of 72.4%, specificity of 71.1%, and accuracy of 71.6%. LDL cholesterol > or =190 mg/dl in subjects with familial or personal histories of TX and > or =220, > or =225, and > or =235 mg/dl in those without such histories aged <30, 30 to 39, and > or =40 years, respectively, showed sensitivity of 91.1%, specificity of 71.1%, and accuracy of 74.2% for a positive genetic diagnosis. This new set of diagnostic criteria for FH was validated in an independent group of 440 subjects from 6 additional Spanish lipid clinics. In conclusion, TX and age-adjusted LDL cholesterol cut-off values have the highest value for clinical diagnosis and indication of genetic testing in FH.

Inflammatory and thrombotic processes are associated with vascular dysfunction in children with familial hypercholesterolemia

BACKGROUND

Evidence suggests that children with familial hypercholesterolemia (FH) have endothelial dysfunction. Inflammatory and haemostatic abnormalities are associated with advanced atherosclerosis and increased cardiovascular events. However, it is unknown whether these abnormalities present in FH children and contribute to their vascular dysfunction.

METHODS AND RESULTS

We studied 38 children with FH (19 males, 19 females aged 14.8+/-0.9 years mean+/-S.E.) and 41 healthy children (controls; 22 males, 19 females aged 15.4+/-0.7 years). Endothelium-dependent reactive hyperemia (RH%) and endothelium-independent nitrate hyperemia dilatation (NH%) were measured by strain gauge plethysmography. Inflammatory and haemostatic parameters were assessed by ELISA. RH% and NH% were significantly reduced in FH compared to controls (91.3+/-9.3% vs. 120.4+/-10.6% and 53.6+/-3.8% vs. 74.5+/-7.4%, p<0.05 for both). Total cholesterol and lipoprotein (a) were increased in FH children compared to controls (282.3+/-8.8 mg/dl vs. 163.8+/-4.6 mg/dl and 11.0[4.6, 30.7]mg/dl vs. 5.24[2.63, 11.0]mg/dl median [IQR] respectively; p<0.001 for both). Intercellular cell adhesion molecule (ICAM-1) and interleukin 1 beta (IL-1 beta) serum levels were increased in FH compared to controls (p<0.05 and <0.001, respectively). Plasminogen activator inhibitor 1 (PAI-1) levels were also higher in FH children (p<0.001). Multivariate analysis revealed that reactive hyperemia was independently associated with nitrate-dependent reactive hyperemia (beta=0.597(0.199), p<0.01), PAI-1(beta=-6.78(2.65), p<0.05), log IL-1 beta (beta=-102.8 (30.2), p<0.01), age (beta=-5.06 (2.35), p<0.05) and FH status (beta=-25.2(10.6), p<0.05) (R(2) for the model: 0.63, p=0.001).

CONCLUSIONS

Inflammatory and haemostatic abnormalities are present in FH children and contribute to the endothelial dysfunction observed in these children.

Detection of Familial Hypercholesterolaemia: A Major Treatment Gap in Preventative Cardiology

Familial hypercholesterolaemia (FH) is a common genetic disorder that untreated has an almost one hundredfold risk of coronary artery disease (CAD). In an audit of 334 patients with premature CAD admitted to a Department of Cardiology, only 60% of medical records had sufficient clinical information for identifying FH. Of those with sufficient information recorded, 54% of patients had possible to definite FH on recognised clinical criteria. Amongst those with FH, only 38% were on statin therapy and only 22% were treated to National Heart Foundation targets. Detection and treatment of FH represents a major gap in coronary prevention.

How can the evaluation of genetic tests be enhanced? Lessons learned from the ACCE framework and evaluating genetic tests in the United Kingdom

Advances in genetic technology are increasing the availability of genetic tests, not only for rare single gene disorders, but also for common diseases such as breast and colo-rectal cancer. Before there can be widespread uptake of these tests, they must be evaluated to confirm the benefits of their use. But how should genetic tests be evaluated, given the speed at which new tests are emerging? One highly influential approach is the analytic validity, clinical validity, clinical utility and ethical, legal and social issues (ACCE) framework, which has provided a benchmark for the evaluation of genetic tests. The approach has been adopted and adapted by the United Kingdom Genetic Testing Network, with the help of the Public Health Genetics Unit in Cambridge, to evaluate new genetic tests for use in the National Health Service. We discuss a number of conceptual, methodological, and practical issues concerning the evaluation of genetic tests, based on lessons learned from applying the ACCE framework and from the UK experience, and make a number of recommendations to further strengthen the evaluation of genetic tests.

Strengthening causal inference in cardiovascular epidemiology through Mendelian randomization

Observational studies have contributed in a major way to understanding modifiable determinants of cardiovascular disease risk, but several examples exist of factors that were identified in observational studies as potentially protecting against coronary heart disease, that in randomized controlled trials had no such effect. The likely reason for misleading findings from observational epidemiological studies is that associations are influenced by confounding, bias, and reverse causation--where disease influences a risk factor, rather than vice versa. Mendelian randomization utilizes genetic variants that serve as proxy measures for modifiable risk factors to allow estimation of the causal influence of the modifiable risk factor in question. We present examples of the use of the Mendelian randomization approach and discuss both the limitations and potentials of this strategy.

A critique of paradoxes in current advice on dietary lipids

Beliefs about credible hypotheses of dietary causes of disease still need well-defined mediators to test for logical proof or disproof. We know that food energy causes transient postprandial oxidative insults that may not be fully reversible. Also, eating vitamin-like 18-carbon polyunsaturated fatty acids (PUFA) in foods maintains the 20- and 22-carbon highly unsaturated fatty acids (HUFA) in tissues. Tissue HUFA form hormone-like mediators that each amplify transient postprandial insults into fatal inflammatory, thrombotic and arrhythmic events in cardiovascular disease, a major preventable cause of death. Similar diet-based amplified events may also occur in other inflammatory proliferative disorders including cancer, dementia, arthritis and asthma. Puzzling paradoxes come from fragmented views of this situation which convey incomplete knowledge in oversimplified messages. Tools now exist to demonstrate successful prevention of two fatal food imbalances with credible dietary preventive interventions, but organizers and financers to help gather the evidence remain unknown. The overall evidence accumulated about diet, disease and death may be nearing a paradigm shift in which prior observed facts remain while beliefs about their accepted interpretation change.

Experiences of guilt and shame in patients with familial hypercholesterolemia: a qualitative interview study

OBJECTIVE

To explore patients' experiences of guilt and shame with regard to how they manage familial hypercholesterolemia.

METHODS

We interviewed 40 men and women diagnosed with heterozygous familial hypercholesterolemia. Data were analyzed by systematic text condensation inspired by Giorgi's phenomenological method.

RESULTS

Participants disclosed their condition as inherited and not caused by an unhealthy lifestyle. They could experience guilt or shame if they violated their own standards for dietary management, or if a cholesterol test was not favorable. Participants had experienced health professionals who they felt had a moralizing attitude when counseling on lifestyle and diets. One group took this as a sign of care. Another group conveyed experiences of being humiliated in consultations.

CONCLUSION

Patients with familial hypercholesterolemia may experience guilt and shame related to how they manage their condition. Health professionals' counseling about lifestyle and diet may induce guilt and shame in patients.

PRACTICE IMPLICATIONS

Health professionals should be sensitive to a patient's readiness for counseling in order to diminish the risk of unintentionally inducing guilt and shame in patients.

The D9N, N291S and S447X variants in the lipoprotein lipase (LPL) gene are not associated with Type III hyperlipidemia

BACKGROUND

Type III hyperlipidemia (Type III HLP) is associated with homozygosity for the epsilon2 allele of the APOE gene. However only about 10% of epsilon2 homozygotes develop Type III HLP and it is assumed that additional genetic and/or environmental factors are required for its development. Common variants in the LPL gene have been proposed as likely genetic co-factors.

METHODS

The frequency of the LPL SNPs D9N, N291S and S447X in 100 patients with hyperlipidemia and APOE2/2 genotype has been determined and compared to that in healthy blood donors and patients with hyperlipidemia.

RESULTS

There were no statistically significant difference in the frequencies of the variants between APOE2/2 patients and controls.

CONCLUSION

It is unlikely that the D9N, N291S or S447X variants in the LPL gene play an important role in the development of Type III HLP.

A Systematic Review and Meta-Analysis of Statin Therapy in Children With Familial Hypercholesterolemia

OBJECTIVE

Functional and morphological changes of the arterial wall already present in young children with heterozygous familial hypercholesterolemia (HeFH) suggest that treatment should be initiated early in life to prevent premature atherosclerotic cardiovascular disease. The purpose of this study was to assess the efficacy and particularly safety of statin therapy in children with HeFH.

METHODS AND RESULTS

We performed a meta-analysis of randomized, double-blind, placebo-controlled trials evaluating statin therapy in children aged 8 to 18 years with HeFH. Six studies (n=798 children) with 12 to 104 weeks of treatment were included. Total cholesterol, LDL cholesterol, and apolipoprotein B were significantly reduced, whereas HDL cholesterol and apolipoprotein A1 were significantly increased by statin therapy. No statistically significant differences were found between statin- and placebo-treated children with respect to the occurrence of adverse events (RR 0.99; 95% CI: 0.79 to 1.25), sexual development (RR of advancing > or = 1 stage in Tanner classification 0.96; 95% CI: 0.79 to 1.17), muscle toxicity (RR of CK > or = 10 times the upper limit of normal [ULN] 1.38; 95% CI: 0.18 to 10.82), or liver toxicity (RR of > or = 3 times the ULN for ASAT 0.98; 95% CI: 0.23 to 4.26 and for ALAT 2.03; 95% CI: 0.24 to 16.95). We found a minimal difference in growth in favor of the statin group (0.33 cm; 95% CI: 0.03 cm to 0.63 cm).

CONCLUSION

In addition to the fact that statin treatment is efficacious, our results support the notion that statin treatment in children with HeFH is safe. Thus, even though further studies are required to assess lifelong safety, statin treatment should be considered for all children aged 8 to 18 with HeFH.

How do patients at risk portray candidates for coronary heart disease? A qualitative interview study

OBJECTIVE

To explore how patients at risk of coronary heart disease (CHD) portray candidates for CHD.

DESIGN

Qualitative interview study.

SETTING

Norway.

SUBJECTS

A total of 20 men and 20 women diagnosed with heterozygous familial hypercholesterolemia (FH) recruited through a lipid clinic.

MAIN OUTCOME MEASURES

Participants' beliefs concerning persons who are considered candidates for CHD.

RESULTS

Some participants believed that CHD could happen to anyone, while the majority conveyed detailed notions of persons they considered to be likely victims of CHD. Participants often portrayed the coronary candidate as someone who was different from themselves. Among those who mentioned gender, all presented the candidate as a man. Some women said that they had to reconcile themselves to being at risk of CHD, since they at first had conceived CHD as a man's disease. While some participants considered their notions to be valid for assessing people's risk of CHD, others questioned how valid their notions were.

CONCLUSION

Doctors should recognize that distancing is a way patients cope with risk and that such a strategy may have psychological and moral reasons. When communicating about risk, doctors should take into account that patients' notions of risk may differ from medical notions of risk.

Family communication regarding inherited high cholesterol: why and how do patients disclose genetic risk?

Inadequate family communication concerning hereditary lipid disorders by index patients (IPs) may prevent their biological relatives from seeking testing and treatment. This lack of disclosure places the relatives at increased risk for cardiovascular disease. The present study, undertaken in the Netherlands, explored the reasons for family disclosure, and how disclosure was approached. Semi-structured interviews with 20 purposely sampled IPs revealed that they generally alerted their first-degree relatives of the genetic risk because they felt morally obliged to do so or because they were advised to do so by a health professional. However, IPs rarely alerted their more distant relatives due to insufficient risk knowledge or fear of being perceived as interfering in their relative's affairs. Furthermore, many IPs stated that they would not seek to persuade a relative to undergo testing out of respect for their autonomy. However, the findings did suggest that less direct methods were used for persuasion. An example would be stressing the severity of the condition. Consequently, the self-reported disclosures were incomplete and unbalanced. Typically, IPs provided information regarding the threat of inherited high cholesterol without furnishing information on means of coping with the risk. As IPs want and need professional support to help them disclose this information to their relatives, we suggest additional research about the ethical, practical and economic possibilities for this support.

Basal plasma concentrations of plant sterols can predict LDL-C response to sitosterol in patients with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is associated with a high risk of coronary heart disease. Pharmacological treatment and diet are both essential for the management of FH. Foods rich in plant sterols (PS) may play an important role in the treatment of patients with these disorders.

OBJECTIVE

To test the effect of the intake of PS on low-density lipoprotein (LDL) concentration, endothelial function (EF) and LDL particle size in 30 patients with FH.

DESIGN

Randomized and crossover dietary intervention study.

SETTING

Tertiary outpatient care.

SUBJECTS

Thirty-eight were recruited, but only 30 were subjected to four low-fat dietary intervention periods, each of 4 weeks.

METHODS

Each intervention had a different content of cholesterol (<150 or 300 mg/day) and sitosterol (<1 or 2 g/day). Lipid response, EF and LDL particle size were analysed after the intervention.

RESULTS

Plasma sitosterol/cholesterol ratio was higher during both plant sterol-rich periods than during the low plant sterols periods. Basal sitosterol concentrations predicted the LDL-cholesterol response during the intake of plant sterol-enriched diets. The change in LDL-cholesterol was significantly greater in subjects in the upper and intermediate tertiles of basal plasma sitosterol concentrations (-21+/-8 mg/dl, P=0.03; -19+/-7 mg/dl, P=0.04, respectively) than in subjects in the lower tertile (8+/-5 mg/dl) when they changed from a low cholesterol diet to a low cholesterol plus plant sterol diet.

CONCLUSION

Our study demonstrates that basal sitosterol values can predict hypolipidemic response in patients with FH.