Estimated Yield of Screening for Heterozygous Familial Hypercholesterolemia With and Without Genetic Testing in US Adults

Reproductive Carrier Screening: Identifying Families at Risk for Familial Hypercholesterolemia in the United States

BACKGROUND

Familial hypercholesterolemia is a treatable genetic condition but remains underdiagnosed. We reviewed the frequency of pathogenic or likely pathogenic (P/LP) variants in the LDLR gene in female individuals receiving reproductive carrier screening.

METHODS

This retrospective observational study included samples from female patients (aged 18-55 years) receiving a 274-gene carrier screening panel from January 2020 to September 2022. LDLR exons and their 10 base pair flanking regions were sequenced. Carrier frequency for P/LP variants was calculated for the entire population and by race/ethnicity. The most common variants and their likely functional effects were evaluated.

RESULTS

A total of 91 637 tests were performed on women with race/ethnicity reported as Asian (8.8%), Black (6.1%), Hispanic (8.5%), White (29.0%), multiple or other (15.0%), and missing (33.0%). Median age was 32.8 years with 83 728 (91%) <40 years. P/LP LDLR variants were identified in 283 samples (1 in 324). No patients were identified with >1 P/LP variant. LDLR carrier frequency was higher in Asian (1 in 191 [95% CI, 1 in 142-258]) compared with White (1 in 417 [95% CI, 1 in 326-533]; P<0.001) or Black groups (1 in 508 [95% CI, 1 in 284-910]; P=0.004). The most common variants differed between populations. Of all variants, at least 25.0% were predicted as null variants.

CONCLUSIONS

P/LP variants in LDLR are common. Expanding the use of reproductive carrier screening to include genes associated with FH presents another opportunity to identify people predisposed to cardiovascular disease.

Familial Hypercholesterolemia Variant and Cardiovascular Risk in Individuals With Elevated Cholesterol

Importance

Familial hypercholesterolemia (FH) is a genetic disorder that often results in severely high low-density lipoprotein cholesterol (LDL-C) and high risk of premature coronary heart disease (CHD). However, the impact of FH variants on CHD risk among individuals with moderately elevated LDL-C is not well quantified.

Objective

To assess CHD risk associated with FH variants among individuals with moderately (130-189 mg/dL) and severely (≥190 mg/dL) elevated LDL-C and to quantify excess CHD deaths attributable to FH variants in US adults.

Design, Setting, and Participants

A total of 21 426 individuals without preexisting CHD from 6 US cohort studies (Atherosclerosis Risk in Communities study, Coronary Artery Risk Development in Young Adults study, Cardiovascular Health Study, Framingham Heart Study Offspring cohort, Jackson Heart Study, and Multi-Ethnic Study of Atherosclerosis) were included, 63 of whom had an FH variant. Data were collected from 1971 to 2018, and the median (IQR) follow-up was 18 (13-28) years. Data were analyzed from March to May 2023.

Exposures

LDL-C, cumulative past LDL-C, FH variant status.

Main Outcomes and Measures

Cox proportional hazards models estimated associations between FH variants and incident CHD. The Cardiovascular Disease Policy Model projected excess CHD deaths associated with FH variants in US adults.

Results

Of the 21 426 individuals without preexisting CHD (mean [SD] age 52.1 [15.5] years; 12 041 [56.2%] female), an FH variant was found in 22 individuals with moderately elevated LDL-C (0.3%) and in 33 individuals with severely elevated LDL-C (2.5%). The adjusted hazard ratios for incident CHD comparing those with and without FH variants were 2.9 (95% CI, 1.4-6.0) and 2.6 (95% CI, 1.4-4.9) among individuals with moderately and severely elevated LDL-C, respectively. The association between FH variants and CHD was slightly attenuated when further adjusting for baseline LDL-C level, whereas the association was no longer statistically significant after adjusting for cumulative past LDL-C exposure. Among US adults 20 years and older with no history of CHD and LDL-C 130 mg/dL or higher, more than 417 000 carry an FH variant and were projected to experience more than 12 000 excess CHD deaths in those with moderately elevated LDL-C and 15 000 in those with severely elevated LDL-C compared with individuals without an FH variant.

Conclusions and Relevance

In this pooled cohort study, the presence of FH variants was associated with a 2-fold higher CHD risk, even when LDL-C was only moderately elevated. The increased CHD risk appeared to be largely explained by the higher cumulative LDL-C exposure in individuals with an FH variant compared to those without. Further research is needed to assess the value of adding genetic testing to traditional phenotypic FH screening.

Genetic Testing for Familial Hypercholesterolemia in Clinical Practice

PURPOSE OF REVIEW

Genetic testing has proven utility in identifying and diagnosing individuals with FH. Here we outline the current landscape of genetic testing for FH, recommendations for testing practices and the efforts underway to improve access, availability, and uptake.

RECENT FINDINGS

Alternatives to the traditional genetic testing and counseling paradigm for FH are being explored including expanding screening programs, testing in primary care and/or cardiology clinics, leveraging electronic communication tools like chatbots, and implementing direct contact approaches to facilitate genetic testing of both probands and at-risk relatives. There is no consensus on if, when, and how genetic testing or accompanying genetic counseling should be provided for FH, though traditional genetic counseling and/or testing in specialty lipid clinics is often recommended in expert statements and professional guidelines. More evidence is needed to determine whether alternative approaches to the implementation of genetic testing for FH may be more effective.

Detection strategies for elevated lipoprotein(a): will implementation let the genie out of the bottle?

PURPOSE OF REVIEW

Elevated Lp(a) level is an important causal risk factor for atherosclerotic cardiovascular disease (ASCVD), principally coronary artery disease. Selective testing for Lp(a) is highly recommended in patients at intermediate and high risk for ASCVD. Lp(a) levels are predominantly genetically determined, and this has implications for cascade testing.

RECENT FINDINGS

Recent studies show that cascade testing is effective in identifying elevated Lp(a) in close relatives of probands with high Lp(a). Apart from selective testing and cascade testing as detection strategies, some recent guidelines recommend testing of Lp(a) in all adults at least once in their lifetime and various implementation strategies have been suggested.

SUMMARY

Hyper-Lp(a) is an important global health problem that can be easily detected. Hyper-Lp(a) meets all the criteria for universal screening except that there is not yet supportive evidence from clinical interventional trials showing a reduction of ASCVD events. The cost-effectiveness of the various detection and implementation strategies need to be further evaluated.

Association of triglyceride-glucose index with atherosclerotic cardiovascular disease and mortality among familial hypercholesterolemia patients

BACKGROUND

Familial hypercholesterolemia (FH) is an inherited metabolic disorder with a high level of low-density lipoprotein cholesterol and the worse prognosis. The triglyceride-glucose (TyG) index, an emerging tool to reflect insulin resistance (IR), is positively associated with a higher risk of atherosclerotic cardiovascular disease (ASCVD) in healthy individuals, but the value of TyG index has never been evaluated in FH patients. This study aimed to determine the association between the TyG index and glucose metabolic indicators, insulin resistance (IR) status, the risk of ASCVD and mortality among FH patients.

METHODS

Data from National Health and Nutrition Examination Survey (NHANES) 1999-2018 were utilized. 941 FH individuals with TyG index information were included and categorized into three groups: < 8.5, 8.5-9.0, and > 9.0. Spearman correlation analysis was used to test the association of TyG index and various established glucose metabolism-related indicators. Logistic and Cox regression analysis were used to assess the association of TyG index with ASCVD and mortality. The possible nonlinear relationships between TyG index and the all-cause or cardiovascular death were further evaluated on a continuous scale with restricted cubic spline (RCS) curves.

RESULTS

TyG index was positively associated with fasting glucose, HbA1c, fasting insulin and the homeostatic model assessment of insulin resistance (HOMA-IR) index (all p < 0.001). The risk of ASCVD increased by 74% with every 1 unit increase of TyG index (95%CI: 1.15-2.63, p = 0.01). During the median 114-month follow-up, 151 all-cause death and 57 cardiovascular death were recorded. Strong U/J-shaped relations were observed according to the RCS results (p = 0.0083 and 0.0046 for all-cause and cardiovascular death). A higher TyG index was independently associated with both all-cause death and cardiovascular death. Results remained similar among FH patients with IR (HOMA-IR ≥ 2.69). Moreover, addition of TyG index showed helpful discrimination of both survival from all-cause death and cardiovascular death (p < 0.05).

CONCLUSION

TyG index was applicable to reflect glucose metabolism status in FH adults, and a high TyG index was an independent risk factor of both ASCVD and mortality.