Targeted genetic testing for familial hypercholesterolaemia using next generation sequencing: a population-based study.

Penny J Norsworthy,Jennifer Biggs,Anne K Soutar,Timothy J Aitman,Laurence Game,Jana Vandrovcova,Andrew D Morris,Generation Scotland,Blair H Smith,David J Porteous,Ellen Ra Thomas,Archie Campbell,Shona M Kerr,Anna F Dominiczak

doi:10.1186/1471-2350-15-70

Abstract

BackgroundFamilial hypercholesterolaemia (FH) is a common Mendelian condition which, untreated, results in premature coronary heart disease. An estimated 88% of FH cases are undiagnosed in the UK. We previously validated a method for FH mutation detection in a lipid clinic population using next generation sequencing (NGS), but this did not address the challenge of identifying index cases in primary care where most undiagnosed patients receive healthcare. Here, we evaluate the targeted use of NGS as a potential route to diagnosis of FH in a primary care population subset selected for hypercholesterolaemia.MethodsWe used microfluidics-based PCR amplification coupled with NGS and multiplex ligation-dependent probe amplification (MLPA) to detect mutations in LDLR, APOB and PCSK9 in three phenotypic groups within the Generation Scotland: Scottish Family Health Study including 193 individuals with high total cholesterol, 232 with moderately high total cholesterol despite cholesterol-lowering therapy, and 192 normocholesterolaemic controls.ResultsPathogenic mutations were found in 2.1% of hypercholesterolaemic individuals, in 2.2% of subjects on cholesterol-lowering therapy and in 42% of their available first-degree relatives. In addition, variants of uncertain clinical significance (VUCS) were detected in 1.4% of the hypercholesterolaemic and cholesterol-lowering therapy groups. No pathogenic variants or VUCS were detected in controls.ConclusionsWe demonstrated that population-based genetic testing using these protocols is able to deliver definitive molecular diagnoses of FH in individuals with high cholesterol or on cholesterol-lowering therapy. The lower cost and labour associated with NGS-based testing may increase the attractiveness of a population-based approach to FH detection compared to genetic testing with conventional sequencing. This could provide one route to increasing the present low percentage of FH cases with a genetic diagnosis.

Highlights

Familial hypercholesterolaemia (FH) is a common Mendelian condition which, untreated, results in premature coronary heart disease
The two missense changes, p.Glu92Lys substitution in Proprotein convertase subtilisin/kexin type 9 (PCSK9) and p.Val765Gly in Low density lipoprotein receptor (LDLR), have not been reported before and further segregation and functional studies will be needed to clarify the pathogenicity of these variants
Since only 13% of patients in the GS:SFHS on cholesterollowering therapy had total cholesterol ≥5.5 mmol/l, further testing of subjects on cholesterol-lowering therapies but with cholesterol

Summary

Introduction

Familial hypercholesterolaemia (FH) is a common Mendelian condition which, untreated, results in premature coronary heart disease. Genetic testing and family cascade screening has been proposed as the most cost-effective strategy for detecting cases of FH [3,5], and for distinguishing monogenic FH from sporadic or polygenic hypercholesterolaemia [6]. This strategy was adopted in the 2008 UK guidelines from the National Institute for Health and Clinical Excellence (NICE) [7]. Implementation of these guidelines in England has been limited due to poor availability, low throughput and high costs of traditional genetic testing, fragmented service delivery and lack of investment in identification of index cases

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