Accuracy of low-density lipoprotein cholesterol estimation at very low levels

2024 Guidelines of the Polish Society of Laboratory Diagnostics and the Polish Lipid Association on laboratory diagnostics of lipid metabolism disorders

Lipid disorders are the most common (even 70%) and worst monitored cardiovascular risk factor (only 1/4 of patients in Poland and in CEE countries are on the low-density lipoprotein cholesterol (LDL-C) goal). To improve this, clear and simple diagnostic criteria should be introduced for all components of the lipid profile. These are the updated guidelines of the two main scientific societies in Poland in the area - the Polish Society of Laboratory Diagnostics (PSLD) and the Polish Lipid Association (PoLA), which, in comparison to those from 2020, introduce few important changes in recommendations (two main lipid targets, new recommendations on LDL-C measurements, calculations new goals for triglycerides, new recommendations on remnants and small dense LDL) that should help the practitioners to be early with the diagnosis of lipid disorders and in the effective monitoring (after therapy initiation), and in the consequence to avoid the first and recurrent cardiovascular events.

A novel equation for the estimation of low-density lipoprotein cholesterol in the Saudi Arabian population: a derivation and validation study

Low-density lipoprotein cholesterol (LDL-C) is typically estimated by the Friedewald equation to guide atherosclerotic cardiovascular disease (ASCVD) management despite its flaws. Martin-Hopkins and Sampson-NIH equations were shown to outperform Friedewald's in various populations. Our aim was to derive a novel equation for accurate LDL-C estimation in Saudi Arabians and to compare it to Friedewald, Martin-Hopkins and Sampson-NIH equations. This is a cross-sectional study on 2245 subjects who were allocated to 2 cohorts; a derivation (1) and a validation cohort (2). Cohort 1 was analyzed in a multiple regression model to derive an equation (equationD) for estimating LDL-C. The agreement between the measured (LDL-CDM) and calculated levels was tested by Bland-Altman analysis, and the biases by absolute error values. Validation of the derived equation was carried out across LDL-C and triglyceride (TG)-stratified groups. The mean LDL-CDM was 3.10 ± 1.07 and 3.09 ± 1.06 mmol/L in cohorts 1 and 2, respectively. The derived equation is: LDL-CD = 0.224 + (TC × 0.919) - (HDL-C × 0.904) - (TG × 0.236) - (age × 0.001) - 0.024. In cohort 2, the mean LDL-C (mmol/L) was estimated as 3.09 ± 1.06 by equationD, 2.85 ± 1.12 by Friedewald, 2.95 ± 1.09 by Martin-Hopkins, and 2.93 ± 1.11 by Sampson-NIH equations; statistically significant differences between direct and calculated LDL-C was observed with the later three equations (P < 0.001). Bland-Altman analysis showed the lowest bias (0.001 mmol/L) with equationD as compared to 0.24, 0.15, and 0.17 mmol/L with Friedewald, Martin-Hopkins, and Sampson-NIH equations, respectively. The absolute errors in all guideline-stratified LDL-C categories was the lowest with equationD, which also showed the best classifier of LDL-C according to guidelines. Moreover, equationD predicted LDL-C levels with the lowest error with TG levels up to 5.63 mmol/L. EquationD topped the other equations in estimating LDL-C in Saudi Arabians as it could permit better estimation when LDL-C is < 2.4 mmol/L, in familial hyperlipidemia, and in hypertriglyceridemia, which improves cardiovascular outcomes in high-risk patients. We recommend further research to validate equationD in a larger dataset and in other populations.

Effects of a physical exercise or motor activity protocol on cognitive function, lipid profile, and BDNF levels in older adults with mild cognitive impairment

This study analyzed the effects of a physical exercise program compared to the complexity of the motor task on the cognitive function, brain-derived neurotrophic factor (BDNF) levels, and lipid profile of older adults with mild cognitive impairment (MCI). Twenty-seven participants were randomized into three intervention groups: Physical Exercise (PE), Motor Task (MT), and Physical Exercise associated with Motor Task (PE + MT). Six months of intervention twice a week resulted in improvements in cognitive function, total cholesterol (TC), and LDL cholesterol (LDL-C) in the PE (p < 0.05). In the PE + MT, in addition to improved cognitive capacity, there was also a reduction in non-HDL cholesterol (NHDL-C) and LDL cholesterol (LDL-C) levels (p < 0.05), while in the MT, the values of TC, NHDL-C, and LDL-C decreased as a result of the intervention. BDNF levels were not affected by the interventions. In conclusion, PE alone or combined with MT is effective in promoting improvements in overall cognitive function and lipid profile in older adults with MCI; and BDNF seems not to be a sensitive marker for people with mild cognitive impairment.

Serum cholesterol levels and the risk of brain natriuretic peptide-diagnosed heart failure in postmenopausal women: a population-based prospective cohort study

OBJECTIVE

Hormonal changes during menopause can disturb serum cholesterol which is closely associated with cardiovascular disease. This study investigated the prospective association between serum cholesterol and heart failure (HF) risk in postmenopausal women.

METHODS

We analyzed data from 1,307 Japanese women, aged 55 to 94 years. All women had no history of HF, and their baseline brain natriuretic peptide (BNP) levels were less than 100 pg/mL. During the follow-ups conducted every 2 years, HF was diagnosed among women who developed BNP of 100 pg/mL or greater. Cox proportional hazard models were applied to calculate hazard ratios and 95% CI of HF for women per their baseline total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol (HDL-C) levels. The Cox regression models were adjusted for age, body mass index, smoking, alcohol drinking, hypertension, diabetes, cardiac murmurs, arrhythmia, stroke or ischemic heart disease, chronic kidney disease, and lipid-lowering agent use.

RESULTS

Within an 8-year median follow-up, 153 participants developed HF. In the multivariable-adjusted model, women with total cholesterol of 240 mg/dL or greater (compared with 160-199 mg/dL) and HDL-C of 100 mg/dL or greater (compared with 50-59 mg/dL) showed an increased risk of HF: hazard ratios (95% CI) = 1.70 (1.04-2.77) and 2.70 (1.10-6.64), respectively. The results remained significant after further adjusting for baseline BNP. No associations were observed with low-density lipoprotein cholesterol.

CONCLUSIONS

Total cholesterol of 240 mg/dL or greater and HDL-C of 100 mg/dL or greater were positively associated with the risk of HF in postmenopausal Japanese women.

Comparison of existing methods of low-density lipoprotein cholesterol estimation in patients with type 2 diabetes mellitus

Introduction

Elevated low-density lipoprotein cholesterol (LDL-C) is an important risk factor for atherosclerotic cardiovascular disease (ASCVD). Direct LDL-C measurement is not widely performed. LDL-C is routinely calculated using the Friedewald equation (FLDL), which is inaccurate at high triglyceride (TG) or low LDL-C levels. We aimed to compare this routine method with other estimation methods in patients with type 2 diabetes mellitus (T2DM), who typically have elevated TG levels and ASCVD risk.

Method

We performed a retrospective cohort study on T2DM patients from a multi-institutional diabetes registry in Singapore from 2013 to 2020. LDL-C values estimated by the equations: FLDL, Martin/Hopkins (MLDL) and Sampson (SLDL) were compared using measures of agreement and correlation. Subgroup analysis comparing estimated LDL-C with directly measured LDL-C (DLDL) was conducted in patients from a single institution. Estimated LDL-C was considered discordant if LDL-C was <1.8mmol/L for the index equation and ≥1.8mmol/L for the comparator.

Results

A total of 154,877 patients were included in the final analysis, and 11,475 patients in the subgroup analysis. All 3 equations demonstrated strong overall correlation and goodness-of-fit. Discordance was 4.21% for FLDL-SLDL and 6.55% for FLDL-MLDL. In the subgroup analysis, discordance was 21.57% for DLDL-FLDL, 17.31% for DLDL-SLDL and 14.44% for DLDL-MLDL. All discordance rates increased at TG levels >4.5mmol/L.

Conclusion

We demonstrated strong correlations between newer methods of LDL-C estimation, FLDL, and DLDL. At higher TG concentrations, no equation performed well. The Martin/Hopkins equation had the least discordance with DLDL, and may minimise misclassification compared with the FLDL and SLDL.

Comparison of low-density lipoprotein cholesterol equations in patients with dyslipidaemia receiving cholesterol ester transfer protein inhibition

AIMS

Low-density lipoprotein (LDL-C) lowering is imperative in cardiovascular disease prevention. We aimed to compare accuracy of three clinically-implemented LDL-C equations in a clinical trial of cholesterol ester transfer protein (CETP) inhibition.

METHODS AND RESULTS

Men and women aged 18-75 years with dyslipidaemia were recruited from 17 sites in the Netherlands and Denmark. Patients were randomly assigned to one of nine groups using various combinations of the CETP inhibitor TA-8995 (obicetrapib), statin therapy, and placebo. In pooled measurements over 12 weeks, we calculated LDL-C by the Friedewald, Martin/Hopkins, and Sampson equations, and compared values with preparative ultracentrifugation (PUC) LDL-C overall and with a special interest in the low LDL-C/high triglycerides subgroup. There were 242 patients contributing 921 observations. Overall median LDL-C differences between estimates and PUC were small: Friedewald, 0.00 (25th, 75th: -0.10, 0.08) mmol/L [0 (-4, 3) mg/dL]; Martin/Hopkins, 0.02 (-0.08, 0.10) mmol/L [1 (-3, 4) mg/dL]; and Sampson, 0.05 (-0.03, 0.15) mmol/L [2 (-1, 6) mg/dL]. In the subgroup with estimated LDL-C <1.8 mmol/L (<70 mg/dL) and triglycerides 1.7-4.5 mmol/L (150-399 mg/dL), the Friedewald equation underestimated LDL-C with a median difference versus PUC of -0.25 (-0.33, -0.10) mmol/L [-10 (-13, -4) mg/dL], whereas the median difference by Martin/Hopkins was 0.00 (-0.08, 0.10) mmol/L [0 (-3, 4) mg/dL] and by Sampson was -0.06 (-0.13, 0.00) mmol/L [-2 (-5, 0) mg/dL]. In this subgroup, the proportion of LDL-C observations <1.8 mmol/L (<70 mg/dL) that were correctly classified compared with PUC was 71.4% by Friedewald vs. 100.0% by Martin/Hopkins and 93.1% by Sampson.

CONCLUSION

In European patients with dyslipidaemia receiving a CETP inhibitor, we found improved LDL-C accuracy using contemporary equations vs. the Friedewald equation, and the greatest accuracy was observed with the Martin/Hopkins equation.

REGISTRATION

ClinicalTrials.gov, NCT01970215.

Association of metabolites of benzene and toluene with lipid profiles in Korean adults: Korean National Environmental Health Survey (2015-2017)

Background

Environmental exposure to benzene and toluene is a suspected risk factor for metabolic disorders among the general adult population. However, the effects of benzene and toluene on blood lipid profiles remain unclear. In this study, we investigated the association between urinary blood lipid profiles and metabolites of benzene and toluene in Korean adults.

Methods

We analyzed the data of 3,423 adults from the Korean National Environmental Health Survey Cycle 3 (2015–2017). We used urinary trans,trans-muconic acid (ttMA) as a biomarker of benzene exposure, and urinary benzylmercapturic acid (BMA) as an indicator of toluene exposure. Multivariate logistic regression analyses were performed to explore the association between blood lipid profiles and urinary metabolites of benzene and toluene. Additionally, we examined the linear relationship and urinary metabolites of benzene and toluene between lipoprotein ratios using multivariate regression analyses.

Results

After adjusting for covariates, the fourth quartile (Q4) of ttMA [odds ratio (OR) (95% confidence interval, CI = 1.599 (1.231, 2.077)] and Q3 of BMA [OR (95% CI) = 1.579 (1.129, 2.208)] were associated with an increased risk of hypertriglyceridemia. However, the Q4 of urinary ttMA [OR (95% CI) = 0.654 (0.446, 0.961)] and Q3 of urinary BMA [OR (95% CI) = 0.619 (0.430, 0.889)] decreased the risk of a high level of low-density lipoprotein cholesterol (LDL-C). Higher urinary ttMA levels were positively associated with the ratio of triglycerides to high-density lipoproteins [Q4 compared to Q1: β = 0.11, 95% CI: (0.02, 0.20)]. Higher urinary metabolite levels were negatively associated with the ratio of low-density lipoprotein to high-density lipoprotein [Q4 of ttMA compared to reference: β = -0.06, 95% CI: (-0.11, -0.01); Q4 of BMA compared to reference: β = -0.13, 95% CI: (-0.19, -0.08)].

Conclusion

Benzene and toluene metabolites were significantly and positively associated with hypertriglyceridemia. However, urinary ttMA and BMA levels were negatively associated with high LDL-C levels. These findings suggest that environmental exposure to benzene and toluene disrupts lipid metabolism in humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-14319-x.

Comparison of low-density lipoprotein cholesterol level calculated using the modified Martin/Hopkins estimation or the Friedewald formula with direct homogeneous assay measured low-density lipoprotein cholesterol

INTRODUCTION

Low-density lipoprotein cholesterol (LDL-C) represents the primary lipoprotein target for reducing cardiovascular risk (CV). The aim of our study is to compare the direct and the calculated LDL-C levels in the range below 1.8 mmol/l and 2.6 mmol/l depending on triglycerides, and to evaluate the variation in remnant lipoprotein cholesterol.

MATERIAL AND METHODS

We investigated 14 906 lipid profiles from fasting blood samples of Hungarian individuals with triglycerides < 4.5 mmol/l. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG) and direct LDL-C were measured by the enzymatic assay. We calculated LDL-C by Friedewald's formula (F-LDL-C) and by using the new Martin/Hopkins estimation (MH-LDL-C).

RESULTS

For F-LDL-C below 1.8 mmol/l, MH-LDL-C was 58% between 1.8 and 2.59 mmol/l when TG was in the range 2.3-4.5 mmol/l. For F-LDL-C below 2.6 mmol/l, the MH-LDL-C concordance was 73% in the same TG range (2.3-4.5 mmol/l. If MH-LDL-C was less than 1.8 mmol/l or between 1.8 and 2.59 mmol/l, the difference between non-HDL-C (TC - HDL-C = AC: atherogenic cholesterol) and (MH)LDL-C was less than 0.8 mmol/l in the TG range below 2.3 mmol/l. The remnant lipoprotein cholesterol values were on average 0.5 mmol/l lower by the Martin/Hopkins estimation compared to the Friedewald's calculation if the TG was above 2.3 mmol/l.

CONCLUSIONS

The Friedewald equation tends to underestimate LDL-C levels in very high and high-risk settings. Our analysis supports the conclusion that in Hungarian patients, LDL-C estimation using the Martin/Hopkins formula, which is validated by the beta-quantification method, yields a more accurate LDL-C value than that calculated by the Friedewald formula.

Lipid measurements in the management of cardiovascular diseases: Practical recommendations a scientific statement from the national lipid association writing group

Lipoprotein measurements are pivotal in the management of patients at risk for atherosclerotic coronary heart disease (CHD) with myocardial infarction and coronary death as the main outcomes, and for atherosclerotic cardiovascular disease (ASCVD), which includes CHD and stroke. Recent developments and changes in guidelines affect optimization of using lipid measures as cardiovascular biomarkers. This scientific statement reviews the pre-analytical, analytical, post-analytical, and clinical aspects of lipoprotein measurements. Highlights include the following: i) It is acceptable to screen with nonfasting lipids. ii) non-high-density lipoprotein HDL-cholesterol (non-HDL-C) is measured reliably in either the fasting or the nonfasting state and can effectively guide ASCVD prevention. iii) low density lipoprotein cholesterol (LDL-C) can be estimated from total cholesterol, high density lipoprotein cholesterol (HDL-C), and triglyceride (TG) measurements. For patients with LDL-C>100 mg/dL and TG ≤150 mg/dL it is reasonable to use the Friedewald formula. However, for those with TG 150-400 mg/dL the Friedewald formula for LDL-C estimation is less accurate. The Martin/Hopkins method is recommended for LDL-C estimation throughout the range of LDL-C levels and up to TG levels of 399 mg/dL. For TG levels ≥400 mg/dL LDL-C estimating equations are currently not recommended and newer methods are being evaluated. iv) When LDL-C or TG screening results are abnormal the clinician should consider obtaining fasting lipids. v) Advanced lipoprotein tests using apolipoprotein B (apoB), LDL Particle Number (LDL-P) or remnant cholesterol may help to guide therapeutic decisions in select patients, but data are limited for patients already on lipid lowering therapy with low LDL-C levels. Better harmonization of advanced lipid measurement methods is needed. Lipid measurements are recommended 4-12 weeks after a change in lipid treatment. Lipid laboratory reports should denote desirable values and specifically identify extremely elevated LDL-C levels (≥190 mg/dL at any age or ≥160 mg/dL in children) as severe hypercholesterolemia. Potentially actionable abnormal lipid test results, including fasting triglycerides (TG) ≥500 mg/dL, should be reported as hypertriglyceridemia. Appropriate use and reporting of lipid tests should improve their utility in the management of persons at high risk for ASCVD events.

PoLA/CFPiP/PCS/PSLD/PSD/PSH guidelines on diagnosis and therapy of lipid disorders in Poland 2021

In Poland there are still nearly 20 million individuals with hypercholesterolaemia, most of them are unaware of their condition; that is also why only ca. 5% of patients with familial hypercholesterolaemia have been diagnosed; that is why other rare cholesterol metabolism disorders are so rarely diagnosed in Poland. Let us hope that these guidelines, being an effect of work of experts representing 6 main scientific societies, as well as the network of PoLA lipid centers being a part of the EAS lipid centers, certification of lipidologists by PoLA, or the growing number of centers for rare diseases, with a network planned by the Ministry of Health, improvements in coordinated care for patients after myocardial infarction (KOS-Zawał), reimbursement of innovative agents, as well as introduction in Poland of an effective primary prevention program, will make improvement in relation to these unmet needs in diagnostics and treatment of lipid disorders possible.

Remnant cholesterol predicts cardiovascular disease beyond LDL and ApoB: a primary prevention study

AIMS

Emerging evidence suggests that remnant cholesterol (RC) promotes atherosclerotic cardiovascular disease (ASCVD). We aimed to estimate RC-related risk beyond low-density lipoprotein cholesterol (LDL-C) and apolipoprotein B (apoB) in patients without known ASCVD.

METHODS AND RESULTS

We pooled data from 17 532 ASCVD-free individuals from the Atherosclerosis Risk in Communities study (n = 9748), the Multi-Ethnic Study of Atherosclerosis (n = 3049), and the Coronary Artery Risk Development in Young Adults (n = 4735). RC was calculated as non-high-density lipoprotein cholesterol (non-HDL-C) minus calculated LDL-C. Adjusted Cox models were used to estimate the risk for incident ASCVD associated with log RC levels. We also performed discordance analyses examining relative ASCVD risk in RC vs. LDL-C discordant/concordant groups using difference in percentile units (>10 units) and clinically relevant LDL-C targets. The mean age of participants was 52.3 ± 17.9 years, 56.7% were women and 34% black. There were 2143 ASCVD events over the median follow-up of 18.7 years. After multivariable adjustment including LDL-C and apoB, log RC was associated with higher ASCVD risk [hazard ratio (HR) 1.65, 95% confidence interval (CI) 1.45-1.89]. Moreover, the discordant high RC/low LDL-C group, but not the low RC/high LDL-C group, was associated with increased ASCVD risk compared to the concordant group (HR 1.21, 95% CI 1.08-1.34). Similar results were shown when examining discordance across clinical cutpoints.

CONCLUSIONS

In ASCVD-free individuals, elevated RC levels were associated with ASCVD independent of traditional risk factors, LDL-C, and apoB levels. The mechanisms of RC association with ASCVD, surprisingly beyond apoB, and the potential value of targeted RC-lowering in primary prevention need to be further investigated.

The Use of Blood Biomarkers in Precision Medicine for the Primary Prevention of Atherosclerotic Cardiovascular Disease: a Review

Introduction

A biomarker is a substance, structure, or process that indicates the presence of a disease, infection, or environmental exposure. Clinically useful biomarkers are measurable, improve diagnostic or prognostic performance, and ultimately aid clinicians in determining the initiation, duration, or magnitude of therapy.

Areas Covered

The purpose of this review is to explore the roles of various blood biomarkers of atherosclerotic cardiovascular disease (ASCVD) and how their use may improve the precision with which clinicians can identify, treat, and ultimately prevent ASCVD. Our review will include lipid biomarkers, markers of cardiac injury and wall stress, markers of inflammation, and a few others.

Expert Opinion

Several biomarkers have recently been highlighted as "risk-enhancing factors" in the 2019 American College of Cardiology/American Heart Association Guideline for the Primary Prevention of ASCVD, which can help guide shared decision-making. These included elevated low-density lipoprotein cholesterol, triglycerides, lipoprotein(a), apolipoprotein B, or high-sensitivity C-reactive protein. However, some other biomarkers mentioned in this review are not commonly used despite showing initial promise as prognostic of ASCVD risk, as it is not clear how treatment decisions should be changed after their measurement among asymptomatic individuals. Future studies should focus on whether biomarker-directed management strategies can improve clinical outcomes.

Monogenic and polygenic causes of low and extremely low LDL-C levels in patients referred to specialty lipid clinics: Genetics of low LDL-C

BACKGROUND

In clinical setting, current standard-of-care does not include genetic testing for patients with low (<50 mg/dL) and extremely low (<20 mg/dL) levels of serum low-density lipoprotein-cholesterol (LDL-C).

OBJECTIVE

We aimed identify the underlying molecular cause - both monogenic and polygenic - of low and extremely low LDL-C levels in a cohort of patients presenting to specialty lipid clinics.

METHODS

Whole exome sequencing was done in patients with low or extremely low LDL-C not due to any secondary causes.

RESULTS

Nine patients (4 women), ranging in age from 25 to 63 years old, with low or extremely low LDL-C levels were evaluated. Median LDL-C was 16 mg/dL (range undetectable - 43), total cholesterol 82 mg/dL (42 - 101), triglycerides 35 mg/dL (19-239), and high-density lipoprotein-cholesterol 45 mg/dL (24-81). Of nine patients, two carried known pathogenic variants in APOB (one stop-gain, one deletion; LDL-C range undetectable -10 mg/dL); three patients had novel APOB heterozygous mutations (two frameshift deletions and one splice site; LDL-C range undectable-13 mg/dL); two had heterozygous APOB frameshift deletions previously reported as variants of unknown significance (LDL-C 18 mg/dL in both patients); one (LDL-C 43 mg/dL) had two heterozygous mutations in PCSK9, both previously reported to be benign; and one patient (LDL-C 16 mg/dL) had the APO E2/E2 genotype along with several variants of unknown significance in genes associated with triglycerides. No patients had an LDL-C polygenic risk score below the 5th percentile (range 26th percentile to 93rd percentile).

CONCLUSION

We found APOB mutations to be the most common molecular defect in patients presenting to lipid clinics with low or extremely low LDL-C . Whether clinical genetic testing and LDL-C polygenic risk scores have any utility - other than diagnostic purposes - for such patients remains unclear. In addition, further efforts may be needed to better reclassify pathogenicity of variants of unknown significance.

Comparison of the effectiveness of Martin's equation, Friedewald's equation, and a Novel equation in low-density lipoprotein cholesterol estimation

Low-density-lipoprotein cholesterol (LDL-C) is the main target in atherosclerotic cardiovascular disease (ASCVD). We aimed to validate and compare a new LDL-C estimation equation with other well-known equations. 177,111 samples were analysed from two contemporary population-based cohorts comprising asymptomatic Korean adults who underwent medical examinations. Performances of the Friedewald (FLDL), Martin (MLDL), and Sampson (SLDL) equations in estimating direct LDL-C by homogenous assay were assessed by measures of concordance (R2, RMSE, and mean absolute difference). Analyses were performed according to various triglyceride (TG) and/or LDL-C strata. Secondary analyses were conducted within dyslipidaemia populations of each database. MLDL was superior or at least similar to other equations regardless of TG/LDL-C, in both the general and dyslipidaemia populations (RMSE = 11.45/9.20 mg/dL; R2 = 0.88/0.91; vs FLDL: RMSE = 13.66/10.42 mg/dL; R2 = 0.82/0.89; vs SLDL: RMSE = 12.36/9.39 mg/dL; R2 = 0.85/0.91, per Gangnam Severance Hospital Check-up/Korea Initiatives on Coronary Artery Calcification data). MLDL had a slight advantage over SLDL with the lowest MADs across the full spectrum of TG levels, whether divided into severe hyper/non-hyper to moderate hypertriglyceridaemia samples or stratified by 100-mg/dL TG intervals, even up to TG values of 500-600 mg/dL. MLDL may be a readily adoptable and cost-effective alternative to direct LDL-C measurement, irrespective of dyslipidaemia status. In populations with relatively high prevalence of mild-to-moderate hypertriglyceridaemia, Martin's equation may be optimal for LDL-C and ASCVD risk estimation.

Calculated values of serum LDL-cholesterol (LDL-C) - for better or worse?

BACKGROUND AND AIMS

The use of Friedewald's formula to calculate serum low-density lipoprotein cholesterol (LDL-C) is well-known to have limitations. A modification of it, in 2013, has been proposed to be superior. However, it was not known whether LDL-C values (calculated by the modified formula) meet laboratory performance criteria for their estimation. This study aimed to evaluate this.

METHODS AND RESULTS

LDL-C values were calculated for 129,821 lipid profiles, using both Friedewald's formula and its modified version. Kappa statistics and intra-class correlation coefficient (ICC) were used to determine degree of agreement between directly measured and calculated values for LDL-C. Bias and total percentage error of the values were calculated. LDL-C concentrations calculated by the modified formula showed a greater degree of agreement with directly measured values (kappa = 0.713) than those calculated by Friedewald's formula (kappa = 0.595). Both the formulae produced values with negative biases (-3.47 for the modified formula and -7.62 for Friedewald's formula) and total percentage errors above the recommended limit of 12% (15.57% for the modified formula and 21.77% for Friedewald's formula). ICC showed that values calculated by the modified formula showed a greater degree of agreement with directly measured values, across a range of LDL-C values.

CONCLUSION

Calculated LDL-C values, using the modified formula, showed better agreement with directly measured values, and less bias and percentage total error than those obtained by use of Friedewald's formula. However, the percentage total error with use of the modified formula exceeded the recommended limit for LDL-C.

Total cholesterol/HDL-cholesterol ratio discordance with LDL-cholesterol and non-HDL-cholesterol and incidence of atherosclerotic cardiovascular disease in primary prevention: The ARIC study

AIMS

The total cholesterol (TC)/high-density lipoprotein (HDL) cholesterol ratio may carry additional information not available in more commonly used single cholesterol measures. Analysis of discordance between lipid parameters might help assess the impact of such additional information on the risk of atherosclerotic cardiovascular disease. We aimed to investigate the role of the TC/HDL-cholesterol ratio in determining atherosclerotic cardiovascular disease risk when discordant with low-density lipoprotein (LDL) cholesterol and non-HDL-cholesterol.

METHODS

We studied 14,403 Atherosclerosis Risk in Communities (ARIC) study participants who were free of atherosclerotic cardiovascular disease at baseline. TC/HDL-cholesterol discordance with LDL-cholesterol (estimated by the novel Martin/Hopkins method) and non-HDL-cholesterol was assessed at five visits and determined by being at or above the median for each lipid parameter. We constructed Cox proportional hazard models to estimate the risk for incident atherosclerotic cardiovascular disease events associated with each lipid concordance/discordance category using a time-varying approach.

RESULTS

Mean age of participants was 54.1 years, 56% women and 25% black. There were 2634 atherosclerotic cardiovascular disease events over a median (interquartile range) follow-up of 24.2 (16.0-25.4) years. Among individuals with LDL-cholesterol and non-HDL-cholesterol less than the median, 26% and 21% had discordant TC/HDL-cholesterol at or above the median, respectively. These individuals had a 24% (hazard ratio (HR) 1.24, 95% confidence interval (CI) 1.09, 1.41) and 29% (HR 1.29, 95% CI 1.13, 1.46) greater risk of incident atherosclerotic cardiovascular disease, respectively, compared to those with TC/HDL-cholesterol less than the median after multivariable adjustment. In individuals with diabetes with LDL-cholesterol or non-HDL-cholesterol less than the median, discordant TC/HDL-cholesterol at or above the median was more prevalent at 48% and 38%, respectively.

CONCLUSION

Clinically significant discordance exists between TC/HDL-cholesterol, available from the standard lipid profile, and the routinely used non-HDL-cholesterol and LDL-cholesterol. Such discordance may help inform atherosclerotic cardiovascular disease risk management, particularly in individuals with diabetes in whom discordance is more common.

Comparing a novel machine learning method to the Friedewald formula and Martin-Hopkins equation for low-density lipoprotein estimation

Background

Low-density lipoprotein cholesterol (LDL-C) is a target for cardiovascular prevention. Contemporary equations for LDL-C estimation have limited accuracy in certain scenarios (high triglycerides [TG], very low LDL-C).

Objectives

We derived a novel method for LDL-C estimation from the standard lipid profile using a machine learning (ML) approach utilizing random forests (the Weill Cornell model). We compared its correlation to direct LDL-C with the Friedewald and Martin-Hopkins equations for LDL-C estimation.

Methods

The study cohort comprised a convenience sample of standard lipid profile measurements (with the directly measured components of total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], and TG) as well as chemical-based direct LDL-C performed on the same day at the New York-Presbyterian Hospital/Weill Cornell Medicine (NYP-WCM). Subsequently, an ML algorithm was used to construct a model for LDL-C estimation. Results are reported on the held-out test set, with correlation coefficients and absolute residuals used to assess model performance.

Results

Between 2005 and 2019, there were 17,500 lipid profiles performed on 10,936 unique individuals (4,456 females; 40.8%) aged 1 to 103. Correlation coefficients between estimated and measured LDL-C values were 0.982 for the Weill Cornell model, compared to 0.950 for Friedewald and 0.962 for the Martin-Hopkins method. The Weill Cornell model was consistently better across subgroups stratified by LDL-C and TG values, including TG >500 and LDL-C <70.

Conclusions

An ML model was found to have a better correlation with direct LDL-C than either the Friedewald formula or Martin-Hopkins equation, including in the setting of elevated TG and very low LDL-C.

Comparison of Novel Equations for Estimating Low-Density Lipoprotein Cholesterol in Patients Undergoing Coronary Angiography

AIM

The importance of precisely quantifying low-density lipoprotein cholesterol (LDL-C) has become more pronounced over the years, with the rise of metabolic syndrome in the population and the reduction in LDL-C treatment goals. This study aims to compare two novel equations indirectly estimating LDL-C and assess their compatibility with Friedewald formula, in a population with high cardiovascular risk.

METHODS

This study is a retrospective analysis of the lipid profiles of 10,006 patients who underwent coronary angiography. LDL-C was calculated using Friedewald, Martin, and Sampson equations, and the compatibility between estimations was compared using methods of concordance and reclassification.

RESULTS

Our findings show that Martin and Sampson equations displayed high rates of upward LDL-C reclassification (10.8% and 7.5%, respectively) when compared with Friedewald equation. In comparison to the Sampson method, Martin also reclassified 3.8 % of patients to a higher LDL-C category. The magnitude of discordance between LDL-C estimates was more pronounced in hypertriglyceridemic patients, and this increased progressively with the reduction in LDL-C. The proportion of patients with LDL-C ＜70 mg/dL reclassified to a higher LDL-C category reached 44% (Sampson vs. Friedewald), 65% (Martin vs. Friedewald), and 37% (Martin vs.Sampson) in those with triglyceride levels between 200 and 399 mg/dL.

CONCLUSIONS

Both Martin and Sampson LDL-C estimates displayed significant proportion of upward discordance with reclassification to higher LDL-C categories compared to Friedewald formula, particularly in patients with elevated triglycerides and low LDL-C, a population in whom more accurate estimation of LDL-C is required. Further studies are warranted to validate the recently developed Sampson equation with comparison to Martin method that tended to more significantly overestimate LDL-C.

Achieving low-density lipoprotein cholesterol targets as assessed by different methods in patients with familial hypercholesterolemia: an analysis from the HELLAS-FH registry

Background

Familial hypercholesterolemia (FH) is characterized by elevated low-density lipoprotein cholesterol (LDL-C) levels and increased cardiovascular disease (CVD) risk. FH patients often have increased lipoprotein(a) [Lp(a)] levels, which further increase CVD risk. Novel methods for accurately calculating LDL-C have been proposed.

Methods

Patients with FH were recruited by a network of Greek sites participating in the HELLAS-FH registry. LDL-C levels were calculated using the Friedewald (LDL-C_F) and the Martin/Hopkins (LDL-C_M/H) equations as well as after correcting LDL-C_M/H for Lp(a) levels [LDL-C_Lp(a)corM/H]. The objective was to compare LDL-C levels and target achievement as estimated by different methods in FH patients.

Results

This analysis included 1620 patients (1423 adults and 197 children). In adults at diagnosis, LDL-C_F and LDL-C_M/H levels were similar [235 ± 70 mg/dL (6.1 ± 1.8 mmol/L) vs 235 ± 69 mg/dL (6.1 ± 1.8 mmol/L), respectively; P = NS], while LDL-C_Lp(a)corM/H levels were non-significantly lower than LDL-C_F [211 ± 61 mg/dL (5.5 ± 1.6 mmol/L); P = 0.432]. In treated adults (n = 966) both LDL-C_F [150 ± 71 mg/dL (3.9 ± 1.8 mmol/L)] and LDL-C_M/H levels [151 ± 70 mg/dL (6.1 ± 1.8 mmol/L); P = 0.746] were similar, whereas LDL-C_Lp(a)corM/H levels were significantly lower than LDL-C_F [121 ± 62 mg/dL (3.1 ± 1.6 mmol/L); P < 0.001]. Target achievement as per latest guidelines in treated patients using the LDL-C_M/H (2.5%) and especially LDL-C_Lp(a)corM/H methods (10.7%) were significantly different than LDL-C_F (2.9%; P < 0.001).

In children, all 3 formulas resulted in similar LDL-C levels, both at diagnosis and in treated patients. However, target achievement by LDL-C_F was lower compared with LDL-C_M/H and LDL-C_Lp(a)corM/H methods (22.1 vs 24.8 vs 33.3%; P < 0.001 for both comparisons).

Conclusion

LDL-C_Lp(a)corM/H results in significantly lower values and higher target achievement rate in both treated adults and children. If validated in clinical trials, LDL-C_Lp(a)corM/H may become the method of choice to more accurately estimate ‘true’ LDL-C levels in FH patients.

Non-HDL Cholesterol Levels in Childhood and Carotid Intima-Media Thickness in Adulthood

BACKGROUND

Elevated non-high-density lipoprotein cholesterol (HDL-C) levels are used to identify children at increased cardiovascular risk, but the use of non-HDL-C in childhood to predict atherosclerosis is unclear. We examined whether the National Heart, Lung, and Blood Institute classification of youth non-HDL-C status predicts high common carotid artery intima-media thickness in adulthood.

METHODS

We analyzed data from 4 prospective cohorts among 4582 children aged 3 to 19 years who were remeasured as adults (mean follow-up of 26 years). Non-HDL-C status in youth and adulthood was classified according to cut points of the National Heart, Lung, and Blood Institute and the National Cholesterol Education Program Adult Treatment Panel III. High carotid intima-media thickness (cIMT) in adulthood was defined as at or above the study visit-, age-, sex-, race-, and cohort-specific 90th percentile of intima-media thickness.

RESULTS

In a log-binomial regression analysis adjusted with age at baseline, sex, cohort, length of follow-up, baseline BMI, and systolic blood pressure, children with dyslipidemic non-HDL-C were at increased risk of high cIMT in adulthood (relative risk [RR], 1.29; 95% confidence interval [CI], 1.07-1.55). Compared with the persistent normal group, the persistent dyslipidemia group (RR, 1.80; 95% CI, 1.37-2.37) and incident dyslipidemia (normal to dyslipidemia) groups (RR, 1.45; 95% CI, 1.07-1.96) had increased risk of high cIMT in adulthood, but the risk was attenuated for the resolution (dyslipidemia to normal) group (RR, 1.17; 95% CI, 0.97-1.41).

CONCLUSIONS

Dyslipidemic non-HDL-C levels predict youth at risk for developing high cIMT in adulthood. Those who resolve their non-HDL-C dyslipidemia by adulthood have normalized risk of developing high cIMT in adulthood.

High-Sensitivity C-Reactive Protein Discordance With Atherogenic Lipid Measures and Incidence of Atherosclerotic Cardiovascular Disease in Primary Prevention: The ARIC Study

Background Inflammation is an independent causal risk factor for atherosclerotic cardiovascular diseases (ASCVDs). However, whether hsCRP (high-sensitivity C-reactive protein) is prognostic across various levels of atherogenic lipid measures such as low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, apolipoprotein B and total cholesterol/high-density lipoprotein cholesterol in primary prevention is unknown. Methods and Results We studied 9748 ARIC (Atherosclerosis Risk in Communities) study participants who were free of ASCVD at baseline (visit 4, 1996-1998) and had measurements of lipids, apolipoprotein B, and hsCRP. We used multivariable adjusted Cox models to estimate the risk of incident ASCVD events associated with hsCRP levels (less than/greater than or equal to median) in individuals where triple lipid measures combined (low-density lipoprotein cholesterol + non-high-density lipoprotein cholesterol + apolipoprotein B) or quadruple measures combined [triple + total cholesterol/high-density lipoprotein cholesterol] were less than versus greater than or equal to median cut points. Mean age of participants was 62.6±5.6 years; 59% women, 22% black. There were 1574 ASCVD events over median (interquartile range) follow-up of 18.4 (12.8-19.5) years, and discordance between hsCRP and lipid measures was prevalent in 50% of the population. hsCRP greater than or equal to median (2.4 mg/L), compared with less than median, was associated with an increased risk of ASCVD in individuals with less than median levels of the triple (adjusted hazard ratio, 1.33; 95% CI, 1.09-1.60) and quadruple (adjusted hazard ratio,1.47; 95% CI, 1.18-1.85) lipid measures. Such increased risk was consistent among individuals with low (<7.5%) or high (≥7.5%) estimated risk by the pooled cohort equation. There were no interactions by sex, diabetes mellitus, or statin use. Conclusions Our findings suggest that inflammation is independently associated with ASCVD regardless of atherogenic lipid levels and pooled cohort equation risk score in individuals without known ASCVD.

Impact of improved low-density lipoprotein cholesterol assessment on guideline classification in the modern treatment era-Results from a racially diverse Brazilian cross-sectional study

BACKGROUND

The Martin/Hopkins low-density lipoprotein cholesterol equation (LDL-C_N) was previously demonstrated as more accurate than Friedewald LDL-C estimation (LDL-C_F) in a North American database not able to take race into account.

OBJECTIVES

We hypothesized that LDL-C_N would be more accurate than LDL-C_F and correlate better with LDL particle number (LDL-P) in a racially diverse Brazilian cohort.

METHODS

We performed a cross-sectional analysis of 4897 participants in the Brazilian Longitudinal Study of Adult Health, assessing LDL-C_F and LDL-C_N accuracy via overlap with ultracentrifugation-based measurement among clinical guideline LDL-C categories as well as mg/dL and percent error differences. We analyzed by triglyceride categories and correlated LDL-C estimation with LDL-P.

RESULTS

LDL-C_N demonstrated improved accuracy at 70 to <100 and <70 mg/dL (P < .001), with large errors ≥20 mg/dL about 9 times more frequent in LDL-C_F at LDL-C <70 mg/dL, mainly due to underestimation. Among individuals with LDL-C <70 mg/dL and triglycerides ≥150 mg/dL, 65% vs 100% of ultracentrifugation-based low-density lipoprotein cholesterol calculation fell within appropriate categories of estimated LDL-C_F and LDL-C_N, respectively (P < .001). Similar results were observed when analyzed for age, sex, and race. Participants at LDL-C <70 and 70 to <100 mg/dL with discordantly elevated LDL-C_N vs LDL-C_F had a 58.5% and 41.5% higher LDL-P than those with concordance (P < .0001), respectively.

CONCLUSIONS

In a diverse Brazilian cohort, LDL-C_N was more accurate than LDL-C_F at low LDL-C and high triglycerides. LDL-C_N may avoid underestimation of LDL-C and better reflect atherogenic lipid burden in low particle size, high particle count states.

Update on low-density lipoprotein cholesterol quantification

PURPOSE OF REVIEW

β-Quantification is considered the reference measurement procedure for low-density lipoprotein cholesterol (LDL-C). However, this technique is time-consuming and thus is inappropriate for routine clinical practice. Therefore, the Friedewald equation or homogeneous assays have been widely utilized. As several pitfalls exist with these two methods, a novel method for estimating LDL-C was developed by Martin et al. RECENT FINDINGS: Martin's method uses a strata-specific median for the triglycerides/very low-density lipoprotein cholesterol (VLDL-C) ratio on the basis of triglycerides and non-HDL-C concentrations. Recent studies show that Martin's method better correlates with β-quantification or homogeneous assays compared with the Friedewald equation, especially with values of triglycerides at least 150 mg/dl and/or LDL-CD less than 70 mg/dl. Such findings have also been demonstrated in other ethnic groups (Japanese and Korean) and disease populations, including diabetes and cardiovascular disease, in which the triglycerides/VLDL-C ratio can be affected.

SUMMARY

For the current therapeutic goal of LDL-C values below 70 mg/dl in high-risk patients, accurate assessment of LDL-C levels at very low levels is required. Martin's method could overcome pitfalls such as underestimation of the Friedewald equation at this level. Further evaluation of the triglycerides/VLDL-C ratio in participants with diverse ethnic backgrounds or clinical conditions would expand the implementation of this novel method.

Validity of a Novel Method for Estimating Low-Density Lipoprotein Cholesterol Levels in Cardiovascular Disease Patients Treated with Statins

AIM

The Friedewald equation is the standard method for estimating low-density lipoprotein cholesterol (LDL-C) levels [LDL-C(F)] and fixes the ratio of triglyceride (TG) to very LDL-C at 5. However, this has been reported to underestimate LDL-C, particularly in patients with LDL-C ＜70 mg/dL. A novel method for LDL-C estimation [LDL-C(M)] using an adjustable factor instead of a fixed value of 5 has recently been proposed. The purpose of this study was to validate LDL-C(M) in Japanese patients with cardiovascular disease (CVD) treated with statins.

METHODS

In 385 consecutive CVD patients treated with statins, LDL-C(M) and LDL-C(F) levels were compared with directly measured LDL-C [LDL-C(D)].

RESULTS

Mean LDL-C(D), LDL-C(F), and LDL-C(M) were 81.7±25.5, 76.4±24.6, and 79.9±24.5 mg/dL, respectively. In all patients, both LDL-C(F) and LDL-C(M) were significantly correlated with LDL-C(D) [LDL-C(F) vs. LDL-C(D): R=0.974, p＜0.001; LDL-C(M) vs. LDL-C(D): R=0.987, p＜0.001]. In patients with LDL-C(D) ＜70 mg/dL, LDL-C(M) showed a better correlation with LDLC(D) compared with LDL-C(F) [LDL-C(M) vs. LDL-C(D): R=0.935, p＜0.001; LDL-C(F) vs. LDLC(D): R=0.868, p＜0.001]. In contrast, the correlation of LDL-C(D) with LDL-C(M) or LDL-C(F) was similar in patients with LDL-C(D) ≥70 mg/dL.

CONCLUSIONS

In Japanese patients with CVD treated with statins, LDL-C level estimated by this novel method might be more accurate than those estimated using the Friedewald equation for LDL-C levels ＜70 mg/dL.

Interplay between circulating nitric oxide and interleukin-17 in elderly outpatients with non-inflammatory conditions

Nitric oxide (NOx) availability in biological systems is associated with either favorable or unfavorable outcomes. In this sense, several studies bring about evidence that unbalanced NOx production may be underlying to the pathophysiology of vascular disorders. Our study investigated the possible association of clinical, biochemical and inflammatory variables with total circulating levels of NOx in elderly patients devoid of major inflammatory conditions. Clinical (demographics, lifestyle, anthropometry, pressoric traits) and biochemical characteristics (lipemic, glycemic and hormonal profiles) were assessed from 168 geriatrics outpatients eligible for primary care for age-related disorders. Furthermore, circulating levels of 10 inflammatory mediators and of NOx were measured. Correlation tests analyzed categorical or continuous traits according to serum NOx and found no association between NOx and any of the clinical or laboratory data but a negative correlation between plasma NOx concentrations and levels of the immune mediator IL17a (r = -0.236; P = 0.004). Evidence for a correlation between circulating NOx and IL17 is already present in the literature, mostly from studies conducted under inflammatory conditions. Our hypothesis is that such negative correlation can be attributed to an endogenous homeostatic system that IL17 production by the constitutively produced NOx from the vascular endothelium.

Quantifying Atherogenic Lipoproteins: Current and Future Challenges in the Era of Personalized Medicine and Very Low Concentrations of LDL Cholesterol. A Consensus Statement from EAS and EFLM

BACKGROUND

The European Atherosclerosis Society-European Federation of Clinical Chemistry and Laboratory Medicine Consensus Panel aims to provide recommendations to optimize atherogenic lipoprotein quantification for cardiovascular risk management.

CONTENT

We critically examined LDL cholesterol, non-HDL cholesterol, apolipoprotein B (apoB), and LDL particle number assays based on key criteria for medical application of biomarkers. (a) Analytical performance: Discordant LDL cholesterol quantification occurs when LDL cholesterol is measured or calculated with different assays, especially in patients with hypertriglyceridemia >175 mg/dL (2 mmol/L) and low LDL cholesterol concentrations <70 mg/dL (1.8 mmol/L). Increased lipoprotein(a) should be excluded in patients not achieving LDL cholesterol goals with treatment. Non-HDL cholesterol includes the atherogenic risk component of remnant cholesterol and can be calculated in a standard nonfasting lipid panel without additional expense. ApoB more accurately reflects LDL particle number. (b) Clinical performance: LDL cholesterol, non-HDL cholesterol, and apoB are comparable predictors of cardiovascular events in prospective population studies and clinical trials; however, discordance analysis of the markers improves risk prediction by adding remnant cholesterol (included in non-HDL cholesterol) and LDL particle number (with apoB) risk components to LDL cholesterol testing. (c) Clinical and cost-effectiveness: There is no consistent evidence yet that non-HDL cholesterol-, apoB-, or LDL particle-targeted treatment reduces the number of cardiovascular events and healthcare-related costs than treatment targeted to LDL cholesterol.

SUMMARY

Follow-up of pre- and on-treatment (measured or calculated) LDL cholesterol concentration in a patient should ideally be performed with the same documented test method. Non-HDL cholesterol (or apoB) should be the secondary treatment target in patients with mild to moderate hypertriglyceridemia, in whom LDL cholesterol measurement or calculation is less accurate and often less predictive of cardiovascular risk. Laboratories should report non-HDL cholesterol in all standard lipid panels.

Usefulness of the Martin Method for Estimation of Low-Density Lipoprotein Cholesterol in Coronary Atherosclerosis

OBJECTIVE

This study was conducted to validate the Martin method in coronary atherosclerosis in comparison with the Friedewald equation.

SUBJECTS AND METHODS

A total of 299 participants with a coronary artery calcium score (CACS) ≥300 and a serum triglyceride (TG) level <400 mg/dL at Seoul National University Hospital Healthcare System Gangnam Center, Seoul, Korea, were enrolled in this study. Low-density lipoprotein cholesterol (LDL-C) was directly measured with a homogeneous assay (DLDL) and estimated by both the Friedewald equation (FLDL) and Martin method (MLDL). Overall concordances between DLDL and LDL-C estimates were calculated as the percent agreement. The McNemar test was used to compare the rate of reclassification of participants with FLDL and MLDL, and to determine which differed significantly from each other.

RESULTS

Overall concordance between DLDL and MLDL was slightly higher than that between DLDL and FLDL (73.2 vs. 70.9%, p < 0.001). The FLDL showed poor performance when the TG level was ≥200 mg/dL, mostly by underestimation, which represented a 64.7% discordance with DLDL. The reclassification rate by MLDL, however, did not exceed 35.3% in all of the TG groups.

CONCLUSIONS

The Martin method to estimate LDL-C using the strata-specific TG:VLDL ratio showed a 2-fold better concordance with LDL-C measured with a direct homogeneous assay in coronary atherosclerosis compared to the Friedewald equation when the TG level was ≥200 mg/dL. This finding suggests that MLDL could be a better alternative for estimating LDL-C compared to FLDL when the TG level is ≥200 mg/dL in coronary atherosclerosis.