Mortality in treated heterozygous familial hypercholesterolaemia: implications for clinical management

Non-invasive vessel examinations in carriers of LDL-receptor defective gene versus non-carriers with newly detected asymptomatic severe hypercholesterolemia

The results of the research of early vascular alterations in LDL-R carriers in comparison with those in non-carriers with severe hypercholesterolemia are controversial.

AIM

To investigate the difference between severe hypercholesterolemia patients that carry LDL-R defective gene and those that do not have it, in their functional (flow-mediated vasodilation) and structural (intima-media thickness of carotid artery and ankle-brachial index) characteristics of arterial wall.

PATIENTS AND METHODS

The study included 120 hypercholesterolemic patients. Biochemistry parameters were studied by routine methods. The flow-mediated vasodilation (%FMD), ankle-brachial index (ABI) and intima-media thickness (IMT) of common carotid artery were determined using Hewlett Packard Sonos 5 500; MedicaSoft. IMT.lab was the software programme used in the study.

RESULTS

There was no significant difference between the groups with respect to total cholesterol, LDL, HDL, Apo-B, Apo-A1, cellular adhesion molecules (sICAM-1, sVCAM-1, sP- and sE-selectine). The Apo-B/Apo A1 index differed significantly (t = 11.23, p < 0.001) between the two groups; there was difference even after adjustment for age. There was no significant difference in the endothelial dependent and independent vasodilatation between the examined groups (p > 0.05). We found a significantly greater carotid IMT and lower ABI in the carriers than the respective parameters in the non-carriers. This significant difference was confirmed after adjustment for age.

CONCLUSION

Our data show that LDL-R carriers have a higher carotid IMT and lower ABI than non-carriers, whereas no difference between the groups was found with respect to the level of lipid parameters and %FMD.

Utility of genetic determinants of lipids and cardiovascular events in assessing risk

The prevention of coronary heart disease (CHD) is a major public-health goal, but disease architecture is such that a larger proportion of clinical events occur among the average majority than among the high-risk minority--the prevention paradox. Genetic findings over the past few years have resulted in the reopening of the old debate on whether an individualized or a population-based approach to prevention is preferable. Genetic testing is an attractive tool for CHD risk prediction because it is a low-cost, high-fidelity technology with multiplex capability. Moreover, by contrast with nongenetic markers, genotype is invariant and determined from conception, which eliminates biological variability and makes prediction from early life possible. Mindful of the prevention paradox, this Review examines the potential applications and challenges of using genetic information for predicting CHD, focusing on lipid risk factors and drawing on experience in the evaluation of nongenetic risk factors as screening tests for CHD. Many of the issues we discuss hold true for any late-onset common disease with modifiable risk factors and proven preventative strategies.

Predictors of the intima-media thickness of carotid artery in asymptomatic newly detected severe hypercholesterolemic patients

BACKGROUND

Data about predictors of intima-media thickness (IMT) of common carotid artery (CCA) in asymptomatic subjects with newly detected severe hypercholesterolemia is scarce.

AIM

This research is aimed at studying the predictors of the IMT of CCA among basic atherogenic risk biomarkers - lipid [total cholesterol (TC), triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein (LDL) cholesterol, Apolipoprotein-B, Apolipoprotein-Ai, Apolipoprotein-B/A(1) index] and non-lipid, [asymmetric dimethylarginine (ADMA), total homocysteine, cell adhesion molecules] in asymptomatic subjects with newly detected severe hypercholesterolemia.

METHODS

Two hundred and fifty asymptomatic patients with severe, newly hypercholesterolemia and 200 controls were evaluated. Hypercholesterolemia was defined as TC > 7.5 mm and LDL cholesterol > 4.9 mm. The ADMA and cell adhesion molecules were determined by ELISA and total homocysteine by high-performance liquid chromatography.

RESULTS

There was significant difference between the two groups in respect to all lipid biomarkers (P<0.001). Hypercholesterolemic patients had significantly higher level of ADMA, sVCAM-1, sICAM-1, IMT (P<0.001), whereas no significant difference was found between two groups with respect to total homocysteine, P-selectin and E-selectin (P>0.05). A strong positive correlation between IMT mean and age (r(xy) = 0.714; P<0.001), Apolipoprotein-B (r(xy) = 0.706; r(xy) < 0.001), Apolipoprotein-B/A(1) (r(xy) = 0.324; P<0.001), ADMA (r(xy) = 0.603; P<0.001) was found. The subsequent linear and multiple regression analysis selected age and Apolipoprotein-B as most significant factors in relation to IMT mean. Apolipoprotein-B is a better factor for assessment of risk, as LDL cholesterol underestimates the risk in asymptomatic subjects with newly detected severe hypercholesterolemia, until more rapid and feasible methods for measurement of small and dense LDL are available.

Familial hypercholesterolemia: current treatment options and patient selection for low-density lipoprotein apheresis

Options for treatment of severe heterozygous and homozygous familial hypercholesterolemia prior to the statin era were limited by significant side effects and morbidity. The advent of both the statins and technology for the selective removal of LDL via apheresis have revolutionized management but challenges remain.

Cascade screening for familial hypercholesterolaemia in Scotland

The publication of the UK National Institute for Health and Clinical Excellence familial hypercholesterolaemia guideline led to a combined meeting of lipidologists and geneticists in Scotland. It was agreed to implement a system of cascade screening for familial heterozygous hypercholesterolaemia based on genetic testing to identify family members of known cases who have not previously been diagnosed and treated. The cascade screening system for familial heterozygous hypercholesterolaemia Scotland is described herein.

Detection of mutations and large rearrangements of the low-density lipoprotein receptor gene in Taiwanese patients with familial hypercholesterolemia

Familial hypercholesterolemia (FH) is commonly caused by mutations in the low-density lipoprotein receptor (LDLR), apolipoprotein B, and proprotein convertase subtilisin/kexin type 9 genes. The study aim was to investigate patients with FH in Taiwan, using molecular diagnostic methods, and compare the abnormalities in the small mutation and large DNA rearrangement subgroups. In total, 102 unrelated probands with FH were tested for mutations by exon-by-exon sequence analysis (EBESA) and multiple ligation-dependent probe amplification (MLPA). EBESA identified gene apolipoprotein B R3500W in 8 probands and 25 mis-sense, 5 nonsense, and 6 frameshift LDLR mutations in 52 probands; 11 were novel mutations. Of the 42 probands with mutations undetected by EBESA, 8 had abnormal MLPA patterns, including 2 with exon 6 to 18 deletions, 2 with exon 9 deletion, 1 with exon 6 to 8 deletions, 1 with exon 11 deletion, 1 with exon 3 to 5 duplications, and 1 with exon 7 to 12 duplications. Pedigree analysis showed mutation cosegregation with hypercholesterolemia in affected family members. Mean lipid profiles and rate of failure to lower LDL cholesterol <100 mg/dl in response to rosuvastatin/ezetimibe treatment were similar in groups with abnormal MLPA patterns and groups carrying nonsense or frameshift mutations. In conclusion, frequency of large LDLR rearrangement was approximately 8% in Taiwanese patients with FH. The response to statin drugs differed between probands with abnormal MLPA patterns and probands carrying mis-sense or undetected mutations.

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.

Cost-effectiveness analysis of the use of a high-intensity statin compared to a low-intensity statin in the management of patients with familial hypercholesterolaemia

OBJECTIVES

To estimate, using probabilistic decision-analytic modelling techniques, the cost effectiveness of treating familial hypercholesterolaemia (FH) patients with high-intensity statins compared to treatment with low-intensity statins. For the purpose of this economic analysis, and based on their known differences, statins were categorised as high intensity if they produce greater LDL-cholesterol reductions than simvastatin 40 mg (e.g., simvastatin 80 mg and appropriate doses of atorvastatin and rosuvastatin or combination of statins + ezetimibe).

METHODS

A lifetime Markov model was developed to estimate the incremental cost per quality adjusted life year (QALY) of treating a hypothetical cohort of 1000 FH patients aged between 20 and 70 years. Baseline coronary heart disease risks reported in the NICE TA 94 on statins, and age-adjusted risk of cardiovascular disease reported in the FH population, were used to populate the model. A meta-analysis estimate of the reduction in cardiovascular events from using high-intensity compared with low-intensity statins was obtained from published trials. Results were interpreted using a cost-effectiveness threshold of pound20 000/QALY.

RESULTS

Fewer cardiovascular events and deaths were predicted to occur in the group treated with higher-intensity statins, and the incremental cost-effectiveness ratio (ICER) was estimated at pound11 103/QALY. The ICER remained below the pound20 000 threshold for 20-39-year-olds and 40-59-year-olds, but rose above this threshold in individuals aged over 60 years. One-way sensitivity analysis showed that results were most sensitive to variation in treatment effect on mortality and the cost of high-intensity statins.

CONCLUSIONS

Modelling demonstrates that high-intensity statins are cost-effective for the treatment of younger FH patients. If, as is likely, the relative price of high-intensity statins fall in the future as they come off patent, then their cost effectiveness will improve further.

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.

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.

The tenacity of the coronary candidate: how people with familial hypercholesterolaemia construct raised cholesterol and coronary heart disease

This article considers how people with familial hypercholesterolaemia (FH), an inherited high cholesterol condition, construct FH, high cholesterol and coronary heart disease (CHD). These data are used to explore some of the more prevalent claims about the expansion of genetic explanations for health and illness and its implications. The article draws on 31 interviews with people with FH undertaken at a large lipid clinic, a specialist outpatient clinic, in the north of England. I argue that interviewees tended to distinguish between their own `hereditary' high cholesterol and other people's `lifestyle induced' high cholesterol as a way to establish their own lack of culpability for their condition. At the same time, however, they strongly emphasized the need to take care of themselves, in particular by adhering to appropriate dietary and lifestyle regimes. Interviewees' accounts of CHD were not strongly framed in genetic terms, but tended to conform to established lay notions encapsulated by the idea of the `coronary candidate'. In sum, having FH does not seem to transform these people's understandings of the causes of high cholesterol or CHD. Their experiences were largely accommodated within existing lay frameworks. The analysis contributes to a growing reappraisal of transformative narratives about genetic knowledge.

Diagnosis scoring for clinical identification of children with heterozygous familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a frequent monogenic condition characterized by progressive atherosclerosis requiring preventive therapy from childhood. In a pediatric setting, heterozygous FH (hFH) in children may not be identified from common forms of hypercholesterolemia (HC).

OBJECTIVE

To elaborate a clinical scoring system for the diagnosis of hFH, defined by the presence of a disease-causing mutation of the gene for the low-density lipoprotein receptor (LDLR).

PATIENTS AND METHODS

A total of 100 unrelated children (6 +/-3 years old, 43 boys, 57 girls) with type IIa HC (LDLC >130 mg/dL) and complete genetic testing (at loci for genes for LDLR, apolipoprotein B, proprotein convertase subtilisin-like kesin type 9, and apolipoprotein E) were selected for score elaboration. Of 60 criteria from clinical records and family questionnaires, predictors of having hFH were estimated by logistic regression analysis. Scores were validated in 38 other unrelated children with HC.

RESULTS

Three independent predictors of hFH were identified according to the LDLR genotype (50 Microt+/50 Microt-): low-density lipoprotein cholesterol before (262 vs 178 mg/dL, P < 0.001) and after (225 vs 142 mg/dL, P < 0.001) 3 months or more of a lipid-lowering diet, combined with parental statin usage (odds ratio 6.2; 95% confidence interval 1.4-28.3; P = 0.018). High precision and accuracy of the scoring system (area under the receiver operating characteristic curve = 0.94; 95% confidence interval 0.91-0.98) were translated into 4 probability classes (definite/probable/possible/improbable hFH) with a false-negative rate of 12%.

CONCLUSIONS

A score distinguishing hFH from common HC provides a simple tool for appropriate clinical decision and care in high-risk children.

Family tracing to identify patients with familial hypercholesterolaemia: the second audit of the Department of Health Familial Hypercholesterolaemia Cascade Testing Project

BACKGROUND

Family tracing is a method recognized to find new patients with familial hypercholesterolaemia (FH). We have implemented family tracing led by FH Nurses and have determined acceptability to patients, feasibility and costs.

METHODS

Nurses were located at five National Health Service (NHS) Trusts; they identified FH patients and offered them family tracing. Responses and test results were recorded on a database and summarized on a family pedigree.

RESULTS

The majority ( approximately 70%) of index cases participated; the proportion was lower when patients had been discharged from the clinics and in metropolitan areas. On average, 34% (range 13-50%) of relatives lived outside the catchment area of the clinics and could not attend the nurse-led FH clinics. Of the previously untested relatives, 76% who lived in the catchment area of the clinic came forward to be tested. One-third of the relatives who came forward for testing were children <or=16 y of age. The proportion of relatives diagnosed as likely to have FH was lower than would be predicted (30% vs. 50%). This was mainly due to the uncertainty of a diagnosis based on lipid measurements. The average cost to identify and test one relative was approximately pound 500 but was higher in the metropolitan areas.

CONCLUSION

Cascade testing for FH in the UK is feasible, acceptable and likely to be cost-effective if it is a routine aspect of clinical care. However, national implementation would require an integrated infrastructure, so that all individuals have access to testing, and specialist services for the management of young people.

Quantitative 3T MR imaging of the descending thoracic aorta: patients with familial hypercholesterolemia have an increased aortic plaque burden despite long-term lipid-lowering therapy

PURPOSE

To compare the aortic plaque burden in patients with heterozygous familial hypercholesterolemia on long-term statin treatment with that of matched control subjects.

MATERIALS AND METHODS

The authors studied 11 heterozygous, nonsmoking, nondiabetic, and nonhypertensive patients with familial hypercholesterolemia (mean age, 44 years +/- 10) who had been receiving cholesterol-lowering management for a mean of 12 years +/- 5, including 8.25 years +/- 4.24 with the highest tolerable doses of a statin (or a statin plus ezetimibe), and 26 age- and sex-matched control subjects with 3T magnetic resonance (MR) imaging of the descending thoracic aorta by using an axial T2-weighted turbo spin-echo sequence.

RESULTS

Quantitative analysis demonstrated that the aortic vessel wall area was significantly larger in patients with familial hypercholesterolemia than in control subjects (123 mm(2) +/- 23 vs 102 mm(2) +/- 18, respectively; P < .007), as was vessel wall thickness (1.63 mm +/- 0.28 vs 1.37 mm +/- 0.16, respectively; P < .001). No significant difference was found between mean values of routine serum lipid and lipoprotein parameters.

CONCLUSIONS

The results of this preliminary study show that patients with heterozygous familial hypercholesterolemia have a higher aortic atherosclerotic plaque burden than control subjects at quantitative MR imaging despite long-term lipid-lowering therapy. This information may help design future studies evaluating plaque burden and cardiovascular risk.

Acute myocardial infarction in an 18 year old South Indian girl with familial hypercholesterolemia: a case report

Familial hypercholesterolemia is a single gene disorder with an autosomal dominant pattern of inheritance. Here we report an 18 year old South Indian girl who presented with myocardial infarction. She had xanthomas and an elevated serum low density lipoprotein cholesterol (LDL-C). Her mother and maternal uncle had died at a young age due to myocardial infarction. Her only sibling, 15 year old younger sister also had xanthomas and an elevated LDL-C. This report is to emphasise the need to clinically recognize xanthomas and its association with elevated LDL-C, premature atherosclerosis and familial inheritance. Early diagnosis and early initiation of treatment will save the affected individual and the other family members.

Diagnosis of heterozygous familial hypercholesterolaemia in children

BACKGROUND

Most children with familial hypercholesterolaemia (FH) are diagnosed by raised blood cholesterol levels, but the test lacks sensitivity and specificity. As such children have evidence of vascular dysfunction at an early age, correct identification of affected individuals is important so that treatment can be started.

AIM

To determine levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in children with genetically proven FH and their unaffected siblings, in order to identify a diagnostic cut-off point if possible.

DESIGN

Retrospective case-note survey.

METHODS

We studied the notes of 115 children aged 3-16 years, 69 proven FH and 46 unaffected sibs, 65 boys and 50 girls, from 31 families and 21 different mutations. Data recorded were age, sex, TC, and (when available) LDL-C.

RESULTS

The lowest TC level in an affected individual was 4.7 mmol/l and the highest in normal individual was 6.05 mmol/l. This overlap range included 21 children (18% of the total). The corresponding figures for LDL-C were 3.0 and 3.7 mmol/l, which included eight children (8%).

CONCLUSION

TC is not an effective test for differentiating affected and unaffected children with FH. LDL-C is better, but genetic testing remains the method of choice, especially if treatment decisions are to be taken.

Health-related quality of life in elderly patients with familial hypercholesterolemia

Objectives:There are very few descriptions on how familial hypercholesterolemia (FH), a genetic disorder with an increased risk of coronary heart disease (CHD), affects older patients. The aim of this study was to analyze the health-related quality of life (HRQoL) of elderly patients with FH.

Methods:All FH patients with the same FH North Karelia-mutation aged 65 and over living in North Karelia province in Eastern Finland were asked to participate in the study in 2003. They were compared with age-standardized controls from the Finnish general population. A total of forty-three elderly FH patients were identified and thirty-seven of them (aged 65 to 84 years, M/F 10/27) agreed to participate. Most of them (27/37) had been diagnosed with CHD. All but one of these FH patients had been using statins for approximately 15 years. HRQoL was assessed with the RAND-36 (SF-36) and 15D instruments.

Results:Despite the clear cardiovascular morbidity and low socioeconomic status, these FH patients enjoyed a similar HRQoL as the age-standardized controls in the general population.

Conclusions:Lifelong hypercholesterolemia was not associated with poorer HRQoL in elderly survivors of FH. These elderly FH individuals were characterized by their healthy lifestyle and long-term statin treatment.

Are patients with familial hypercholesterolaemia well managed in lipid clinics? An audit of eleven clinics from the Department of Health Familial Hypercholesterolaemia Cascade Testing project

Background

Familial hypercholesterolaemia (FH) is an autosomal co-dominant disorder which is relatively common, leads to high levels of LDL-cholesterol and if untreated to early coronary heart disease. An audit of current practice at National Health Service Trusts in England was undertaken to determine whether FH patients meet the diagnostic criteria for FH; are being offered appropriate advice and treatment; and to what extent their families are contacted and offered testing for the disorder.

Methods

Medical records of known FH patients (over 18 years of age and diagnosed before 31 December 2003) were accessed to obtain information on diagnosis, treatment and family tracing.

Results

The records of 733 FH patients were examined, 79% met the UK ‘Simon Broome’ register criteria for the diagnosis of definite or possible FH. Analyses showed that patients were usually offered appropriate advice and treatment, with 89% being on a statin. However, the audit indicated a high variability in family tracing between the sites, with significant differences in the frequency of inclusion of a family pedigree in the notes (range 1–71%, mean 35%); the general practitioner (GP) being advised that first-degree relatives should be tested (range 4–52%, mean 27%); and the proportion of relatives contacted and tested (range 6–50%, mean 32%).

Conclusion

FH patients are well cared for in lipid clinics in England, are being given appropriate lifestyle advice and medication, but an increase in recording of LDL-cholesterol levels may lead to improvements in their management. Practice in family tracing appears to vary widely between clinics.

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.

A rare polymorphism in the low density lipoprotein (LDL) gene that affects mRNA splicing

Familial hypercholesterolaemia (FH) is usually caused by mutations in the low density lipoprotein (LDL) receptor gene (LDLR) that impair clearance of LDL from the circulation. The increased risk of premature coronary heart disease associated with FH can be reduced by dietary advice and treatment with lipid-lowering drug therapy, but it is important to identify affected individuals at an early stage. Several programmes for genetic diagnosis of FH that rely on identifying nucleotide substitutions in genomic DNA have been initiated, but the validity of these is dependent on distinguishing between a silent nucleotide variant and a mutation that affects LDL-receptor function. Here we describe a single nucleotide substitution in the coding region of exon 9 of LDLR that is an apparently silent polymorphism: CGG (Arg406) to AGG (Arg). Analysis of mRNA from the patient's cells showed that the mutation introduces a new splice site that is used to the exclusion of the natural splice site and causes a deletion of 31 bp from the mRNA, predicted to introduce premature termination four codons after R406. This finding emphasizes the caution needed in genetic diagnosis of FH based on genomic DNA sequence alone.

Effect of ezetimibe coadministered with statins in genotype-confirmed heterozygous FH patients

We investigated the effect of statins and statins plus ezetimibe in 65 FH heterozygotes carrying LDLR-defective or LDLR-negative mutations as well as the effect of ezetimibe monotherapy in 50 hypercholesterolemic (HCH) patients intolerant to statins. PCSK9 and NPC1L1 genes were analysed to assess the role of genetic variants in response to therapy. In FH patients combined therapy reduced LDL-C by 57%, irrespective of the type of LDLR mutation. The additional decrease of plasma LDL-C induced by ezetimibe showed wide inter-individual variability (from -39% to -4.7%) and was negatively correlated with percent LDL-C decrease due to statin alone (r=-0.713, P<0.001). The variable response to statins was not due to PCSK9 gene variants associated with statin hyper-sensitivity. The highest response to ezetimibe was observed in a carrier of R174H substitution in NPC1L1, which had been found to be associated with high cholesterol absorption. In HCH patients, ezetimibe monotherapy induced a variable decrease of plasma LDL-C (from -47.7% to -13.4%). To investigate this variability, we sequenced NPC1L1 gene in patients with the highest and the lowest response to ezetimibe. This analysis showed a higher prevalence of the G allele of the c.816 C>G polymorphism (L272L) in hyper-responders, an observation confirmed also in FH patients hyper-responders to ezetimibe. In both FH and HCH patients, the G allele carriers tended to have a higher LDL-C reduction in response to ezetimibe. These observations suggest that in FH heterozygotes LDL-C reduction following combined therapy reflects a complex interplay between hepatic synthesis and intestinal absorption of cholesterol.