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

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.

Polygenic Versus Monogenic Causes of Hypercholesterolemia Ascertained Clinically

“…12 For instance, 35% to 65% of patients in other clinically ascertained hypercholesterolemia cohorts of various ethnic backgrounds were FH mutation-positive by DNA sequencing, [13][14][15] in contrast to only 2.4% of individuals with total cholesterol >7 mmol/L (>271 mg/dL) ascertained agnostically in a population-based study. 16 This disparity was proposed to be related to enrichment for FH mutation-positive individuals through the medical referral process combined with unavailability of other prioritizing clinical data, such as family history in population-based samples. 6 Also, unmeasured types of variation, such as CNVs and polygenic effects, may be present in a high proportion of hypercholesterolemic individuals from population-based samples.…”

“…16,17 Both weighted and unweighted GRS (wGRS and uwGRS, respectively) were calculated; for the former, the weighting factors were the published beta-coefficients for per-allele change in LDL cholesterol. 7 .…”

Sorting the Wheat from the Chaff in Familial Hypercholesterolemia

“…However, the ultimate yield of this approach for FH has been questioned, noting other work by Futema et al in which they were unable to find new FH loci in 125 unrelated mutationnegative definite FH patients (15 ). Screening for FH causing mutation testing in individuals with ostensible hypercholesterolemia in the community gives an exceptionally low yield of Ͻ5% (16 ), implying that most of these disorders are PHC and supporting the main thesis of the work presented.…”

Research Article Mutational screening in the LDLR gene among patients presenting familial hypercholesterolemia in the Southeast of Brazil.

“…On the other hand, in a population where no founder effect was detected or in a population where we find a great genetic heterogeneity, the gold-standard approach remains on the full sequencing of the LDLR-coding region followed by the search of APOB and PCSK9 gene defects (Izar et al, 2010). A recent study using the next-generation sequencing (NGS) to screen for a mutation in the three genes LDLR, APOB, and PCSK9 say that the NGS methodology could provide one rapid route to increasing the present low percentage of FH cases with a genetic diagnosis (Norsworthy et al, 2014). Regarding the seven patients who showed no mutations, the presence of the FH may probably be associated with other genes as APOB and PCSK9, as mutations in these two other genes cause patients presenting a similar phenotype to the ones with mutations in LDLR (Austin et al, 2004;Slimani et al, 2012).…”