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The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently addressed present and future challenges in the laboratory diagnostics of atherogenic lipoproteins. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDLC), LDL cholesterol (LDLC), and calculated non-HDLC (=total - HDLC) constitute the primary lipid panel for estimating risk of atherosclerotic cardiovascular disease (ASCVD) and can be measured in the nonfasting state. LDLC is the primary target of lipid-lowering therapies. For on-treatment follow-up, LDLC shall be measured or calculated by the same method to attenuate errors in treatment decisions due to marked between-method variations. Lipoprotein(a) [Lp(a)]-cholesterol is part of measured or calculated LDLC and should be estimated at least once in all patients at risk of ASCVD, especially in those whose LDLC declines poorly upon statin treatment. Residual risk of ASCVD even under optimal LDL-lowering treatment should be also assessed by non-HDLC or apolipoprotein B (apoB), especially in patients with mild-to-moderate hypertriglyceridemia (2-10 mmol/L). Non-HDLC includes the assessment of remnant lipoprotein cholesterol and shall be reported in all standard lipid panels. Additional apoB measurement can detect elevated LDL particle (LDLP) numbers often unidentified on the basis of LDLC alone. Reference intervals of lipids, lipoproteins, and apolipoproteins are reported for European men and women aged 20-100 years. However, laboratories shall flag abnormal lipid values with reference to therapeutic decision thresholds.

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., (© 2018 American Association for Clinical Chemistry.)

Objectives: This study sought to define the relationship between oxidative biomarkers, cardiovascular disease (CVD) risk factors, and inflammatory and thrombosis biomarkers., Background: Elevated levels of oxidized phospholipids (OxPL) on apolipoprotein B particles (apoB) represent a novel biomarker of CVD. Previous studies suggest that an increase in OxPL/apoB reflects a positive response to statins and a low-fat diet., Methods: This study measured OxPL/apoB, lipoprotein (a) [Lp(a)], and oxidized low-density lipoprotein (OxLDL) biomarkers, consisting of immunoglobulin (Ig)G and IgM autoantibodies to malondialdehyde (MDA)-low-density lipoprotein (LDL) and IgG and IgM apoB-100 immune complexes (IC/apoB), at baseline and after 16 weeks of treatment with atorvastatin 80 mg/day or placebo in 2,342 patients with acute coronary syndromes (ACS) enrolled in the MIRACL (Myocardial Ischemia Reduction With Aggressive Cholesterol Lowering) trial., Results: At baseline, potentially atheroprotective IgM autoantibodies and IgM IC/apoB were lower in male patients, diabetic patients, and patients >65 years of age. Patients with an LDL level greater than the median (122 mg/dl) had higher levels of OxPL/apoB, Lp(a), and OxLDL biomarkers compared with those who had an LDL level less than the median. Atorvastatin resulted in significantly larger changes in all biomarkers in female patients, patients age <65 years, patients with LDL cholesterol <122 mg/dl, nonsmokers, and nondiabetic patients (p < 0.0001 for all). In particular, a significant increase in OxPL/apoB in response to atorvastatin was noted in all 20 subgroups evaluated. Weak or no significant correlations were noted between all OxLDL biomarkers and C-reactive protein, serum amyloid A, tissue plasminogen activator, interleukin-6, intercellular adhesion molecule, vascular cell adhesion molecule, P-selectin, and E-selectin at randomization and 16 weeks., Conclusions: In patients with ACS, baseline levels of oxidative biomarkers varied according to specific CVD risk factors and were largely independent of inflammatory biomarkers. Atorvastatin uniformly increased OxPL/apoB levels in all subgroups studied. Future studies are warranted to assess whether the increase in OxPL/apoB levels reflects the benefit of effective therapeutic interventions and prediction of new CVD events.

Background: National Cholesterol Education Program (NCEP) guidelines recommend development of direct assays for LDL cholesterol (LDL-C) measurement, but it is unclear how these assays compare with Friedewald calculation in predicting cardiovascular disease (CVD)., Methods: In a study of 27 331 healthy women with triglycerides

Background: Although guidelines recommend measuring fasting lipids for initial screening of adults without cardiovascular disease (CVD), recent studies suggest that nonfasting triglycerides may be superior to fasting. Whether fasting status alters associations of nontriglyceride lipids with CVD is unclear., Methods and Results: In a prospective study of 26 330 healthy women (19 983 fasting; 6347 nonfasting), associations of baseline lipids with incident CVD (754 fasting; 207 nonfasting) were examined over an 11-year follow-up. Except for triglycerides, lipid concentrations differed minimally (<5%) for fasting versus nonfasting. However, stronger associations with CVD were noted for fasting total cholesterol (adjusted fasting hazard ratio [HR], 1.22 per 1-SD increment; 95% CI, 1.14 to 1.30; nonfasting HR, 1.07; 95% CI, 0.93 to 1.21), low-density lipoprotein (LDL) cholesterol (fasting HR, 1.21; 95% CI, 1.13 to 1.29; nonfasting HR, 1.00; 95% CI, 0.87 to 1.15), apolipoprotein B-100 (fasting HR, 1.36; 95% CI, 1.27 to 1.45; nonfasting HR, 1.20; 95% CI, 1.05 to 1.36), non-high-density lipoprotein (HDL) cholesterol (fasting HR, 1.29; 95% CI, 1.21 to 1.38; nonfasting HR, 1.15; 95% CI, 1.01 to 1.31), and apolipoprotein B-100/A-1 ratio (fasting HR, 1.39; 95% CI, 1.30 to 1.48; nonfasting HR, 1.18; 95% CI, 1.09 to 1.27). Compared with fasting levels, nonfasting HDL cholesterol, apolipoprotein A-1, and total/HDL cholesterol ratio had similar associations, and triglycerides had a stronger association, with CVD. Significant interactions were seen for LDL cholesterol and apolipoprotein B-100/A-1 ratio with fasting status (P for interaction=0.03 and <0.001, respectively)., Conclusions: This study demonstrates that HDL cholesterol, triglycerides, total/HDL cholesterol ratio, and apolipoprotein A-1 predict CVD when measured nonfasting. By contrast, total, LDL, and non-HDL cholesterol, in addition to apolipoprotein B-100 and B-100/A-1 ratio, provide less useful CVD risk information when nonfasting, despite small changes in their concentrations. Guidelines for lipid screening may need to consider these differences.

This prospective study assessed the clinical application of a nonfasting low-density lipoprotein cholesterol measure in a pediatric primary care population. A homogenous direct low-density lipoprotein cholesterol assay was tested in healthy children, aged 4 to 12 years, at risk for hyperlipidemia, as defined by American Academy of Pediatrics, and including patients with incomplete family histories. This nonfasting homogeneous assay was comparable to modified beta quantification, the gold standard reference method of measuring low-density lipoprotein cholesterol, and the current recommended screening method, total cholesterol. Results from the study suggest that this nonfasting assay can provide more direct low-density lipoprotein cholesterol measurements for healthy children, with improved clinical utility and greater overall patient convenience in testing for important cholesterol abnormalities.

Background: Apolipoprotein B (apoB) plasma levels reflect the concentration of proatherogenic lipoproteins very low-density lipoprotein and low-density lipoprotein (LDL), whereas non-high-density lipoprotein cholesterol (non-HDL-C) levels reflect the concentration of cholesterol transported by these particles., Methods and Results: The aim of our study was to compare apoB, non-HDL-C, LDL cholesterol (LDL-C), and other lipid markers as predictors of coronary heart disease (CHD) in a nested case-control study among 18 225 participants in the Health Professionals Follow-up Study. Among men who were free of diagnosed cardiovascular disease at the time of blood collection, 266 had nonfatal myocardial infarction or fatal CHD during 6 years of follow-up. Through the use of risk set sampling, control subjects were selected at a 2:1 ratio and matched with regard to age, date of blood collection, and smoking status. After adjustment for matching factors, the relative risk of CHD in the highest quintile compared with the lowest quintile was 2.76 (95% confidence interval [CI], 1.66 to 4.58) for non-HDL-C, 3.01 (95% CI, 1.81 to 5.00) for apoB, 1.81 (95% CI, 1.12 to 2.93) for LDL-C, 0.31 (95% CI, 0.18 to 0.52) for HDL-C, 2.41 (95% CI, 1.43 to 4.07) for triglycerides (all P trend <0.001), and 1.42 (95% CI, 0.86 to 2.32, P trend =0.19) for lipoprotein(a). When non-HDL-C and LDL-C were mutually adjusted, only non-HDL-C was predictive of CHD. When non-HDL-C and apoB were mutually adjusted, only apoB was predictive; the relative risk was 4.18 (95% CI, 1.30 to 13.49; P trend =0.02) for apoB compared with 0.70 (95% CI, 0.21 to 2.27; P trend =0.72) for non-HDL-C. Triglycerides added significant information to non-HDL-C but not to apoB for CHD risk prediction., Conclusions: Although non-HDL-C and apoB were both strong predictors of CHD in this male cohort, more so than LDL-C, the findings support the concept that the plasma concentration of atherogenic lipoprotein particles measured by apoB is more predictive in development of CHD than the cholesterol carried by these particles, measured by non-HDL-C.

Objectives: The aim of this research was to compare relative efficacy of different statin regimens in achieving the dual goals of low-density lipoprotein cholesterol (LDL-C) and C-reactive protein (CRP) reduction., Background: While secondary prevention guidelines for statin therapy suggest lowering LDL-C levels <70 mg/dl, we have recently shown that clinical outcomes are improved when CRP levels are also lowered <2 mg/l., Methods: We addressed the relative efficacy of pravastatin 40 mg and atorvastatin 80 mg daily to reduce LDL-C and CRP among 3,745 acute coronary syndrome patients., Results: A total of 1,018 participants (27.1%) achieved the dual goals of LDL-C <70 mg/dl and CRP <2 mg/l. After adjustment for age, gender, smoking, diabetes, hypertension, obesity, and HDL-C, these individuals had a 28% lower risk of recurrent myocardial infarction or vascular death (relative risk = 0.72; 95% confidence interval 0.52 to 0.99). Of those who achieved dual goals, 80.6% received atorvastatin 80 mg, while 19.4% received pravastatin 40 mg (p < 0.001). Only 11% allocated pravastatin and 44% allocated atorvastatin achieved the goals of LDL-C <70 mg/dl and CRP <2 mg/l, and only 5.8% allocated pravastatin 40 mg and 26.1% allocated atorvastatin 80 mg reached the even lower goals of LDL-C <70 mg/dl and CRP <1 mg/l. The correlation coefficient for CRP measured at 30 days and at end of study was 0.61 (p < 0.001), a value almost identical to that for LDL-C over the same follow-up period (r = 0.62, p < 0.001)., Conclusions: While atorvastatin 80 mg was superior to pravastatin 40 mg in terms of achieving the dual goals of aggressive LDL-C and CRP reduction, neither agent brought the majority of patients below thresholds needed to maximize patient benefit.

Background: Statins lower the levels of low-density lipoprotein (LDL) cholesterol and C-reactive protein (CRP). Whether this latter property affects clinical outcomes is unknown., Methods: We evaluated relationships between the LDL cholesterol and CRP levels achieved after treatment with 80 mg of atorvastatin or 40 mg of pravastatin per day and the risk of recurrent myocardial infarction or death from coronary causes among 3745 patients with acute coronary syndromes., Results: Patients in whom statin therapy resulted in LDL cholesterol levels of less than 70 mg per deciliter (1.8 mmol per liter) had lower event rates than those with higher levels (2.7 vs. 4.0 events per 100 person-years, P=0.008). However, a virtually identical difference was observed between those who had CRP levels of less than 2 mg per liter after statin therapy and those who had higher levels (2.8 vs. 3.9 events per 100 person-years, P=0.006), an effect present at all levels of LDL cholesterol achieved. For patients with post-treatment LDL cholesterol levels of more than 70 mg per deciliter, the rates of recurrent events were 4.6 per 100 person-years among those with CRP levels of more than 2 mg per liter and 3.2 events per 100 person-years among those with CRP levels of less than 2 mg per liter; the respective rates among those with LDL cholesterol levels of less than 70 mg per deciliter were 3.1 and 2.4 events per 100 person-years (P<0.001). Although atorvastatin was more likely than pravastatin to result in low levels of LDL cholesterol and CRP, meeting these targets was more important in determining the outcomes than was the specific choice of therapy. Patients who had LDL cholesterol levels of less than 70 mg per deciliter and CRP levels of less than 1 mg per liter after statin therapy had the lowest rate of recurrent events (1.9 per 100 person-years)., Conclusions: Patients who have low CRP levels after statin therapy have better clinical outcomes than those with higher CRP levels, regardless of the resultant level of LDL cholesterol. Strategies to lower cardiovascular risk with statins should include monitoring CRP as well as cholesterol., (Copyright 2005 Massachusetts Medical Society.)

Aim: Recent data suggests that LDL particle concentration, as determined by Nuclear Magnetic Resonance (NMR) spectroscopy, may be associated with cardiovascular risk. We sought to determine the effect of randomization to pravastatin therapy on LDL particle concentration-NMR, among a primary prevention population., Methods and Results: LDL particle concentration-NMR, LDL size-NMR, and standard chemical lipid parameters were measured at baseline and after 12 weeks among 500 individuals without overt coronary disease randomly allocated to pravastatin 40mg (n=256) or placebo (n=244). Randomization to pravastatin therapy caused a 19% reduction in median LDL particle concentration-NMR at 12 weeks, as compared to a 4.2% increase among those randomized to placebo (P<0.001 for pravastatin group compared to placebo). Pravastatin therapy caused a median 24.9% reduction in LDL cholesterol measured chemically compared to a 0.9% increase in the placebo group (P<0.001). Pravastatin therapy did not cause a significant change in median LDL size-NMR (0.5% increase in pravastatin group vs 0.0% in placebo group; P=0.25). The change in LDL particle concentration with pravastatin correlated inversely with baseline LDL size (r=-0.24; P<0.001) such that the largest reduction in LDL particle concentration-NMR was among those with the smallest LDL size-NMR at baseline (median% change =21.4% for tertile 1 of LDL size, 19.9% for tertile 2, and 16.5% for tertile 3; P=0.03). In contrast, pravastatin-induced changes in LDL cholesterol did not correlate with baseline LDL size-NMR (r=-0.05; P=0.47)., Conclusion: Among individuals without overt hyperlipidemia or known coronary artery disease, randomized allocation to pravastatin (40mg) therapy for 12 weeks caused a reduction in LDL particle concentration-NMR, the magnitude of which was dependent on baseline LDL size-NMR.

Background: Both C-reactive protein and low-density lipoprotein (LDL) cholesterol levels are elevated in persons at risk for cardiovascular events. However, population-based data directly comparing these two biologic markers are not available., Methods: C-reactive protein and LDL cholesterol were measured at base line in 27,939 apparently healthy American women, who were then followed for a mean of eight years for the occurrence of myocardial infarction, ischemic stroke, coronary revascularization, or death from cardiovascular causes. We assessed the value of these two measurements in predicting the risk of cardiovascular events in the study population., Results: Although C-reactive protein and LDL cholesterol were minimally correlated (r=0.08), base-line levels of each had a strong linear relation with the incidence of cardiovascular events. After adjustment for age, smoking status, the presence or absence of diabetes mellitus, categorical levels of blood pressure, and use or nonuse of hormone-replacement therapy, the relative risks of first cardiovascular events according to increasing quintiles of C-reactive protein, as compared with the women in the lowest quintile, were 1.4, 1.6, 2.0, and 2.3 (P<0.001), whereas the corresponding relative risks in increasing quintiles of LDL cholesterol, as compared with the lowest, were 0.9, 1.1, 1.3, and 1.5 (P<0.001). Similar effects were observed in separate analyses of each component of the composite end point and among users and nonusers of hormone-replacement therapy. Overall, 77 percent of all events occurred among women with LDL cholesterol levels below 160 mg per deciliter (4.14 mmol per liter), and 46 percent occurred among those with LDL cholesterol levels below 130 mg per deciliter (3.36 mmol per liter). By contrast, because C-reactive protein and LDL cholesterol measurements tended to identify different high-risk groups, screening for both biologic markers provided better prognostic information than screening for either alone. Independent effects were also observed for C-reactive protein in analyses adjusted for all components of the Framingham risk score., Conclusions: These data suggest that the C-reactive protein level is a stronger predictor of cardiovascular events than the LDL cholesterol level and that it adds prognostic information to that conveyed by the Framingham risk score., (Copyright 2002 Massachusetts Medical Society)

Background: Because LDL-cholesterol (LDL-C) is a modifiable risk for coronary heart disease, its routine measurement is recommended in the evaluation and management of hypercholesterolemia. We critically examine here the new homogeneous assays for direct determination of LDL-C., Approach: This review relies on published studies and data of the authors using research and routine methods for LDL-C determination. We review experience with methods from their earlier use in lipid research laboratories through the transition to routine clinical testing and the recent development of homogeneous assays. We focus on comparative evaluations and characterizations and the performance of the assays., Content: Homogeneous assays seem to be able to meet current National Cholesterol Education Program (NCEP) requirements for LDL-C testing for precision (CV <4%) and accuracy (bias <4%), when samples collected from nonfasting individuals are used. In addition, all five currently available assays have been certified by the Cholesterol Reference Methods Laboratory Network. The homogeneous methods also appear to better classify individuals into NCEP cutpoints than the Friedewald calculation. However, the limited evaluations to date raise questions about their reliability and specificity, especially in samples with atypical lipoproteins., Conclusions: Available evidence supports recommending the homogeneous assays for LDL-C to supplement the Friedewald calculation in those cases where the calculation is known to be unreliable, e.g., triglycerides >4000 mg/L. Before the homogeneous assays can be confidently recommended to replace the calculation in routine practice, more evaluation is needed.

The diagnosis and management of adults with hypercholesterolemia in the US are largely based on low-density lipoprotein cholesterol (LDL-C) concentration. In order to classify someone correctly into the National Cholesterol Education Program cut-points, LDL-C must be measured with a total error of

Background: LDL-cholesterol (LDL-C) concentrations currently are determined in most clinical laboratories using the Friedewald calculation. This approach has several limitations and may not always meet the current total error recommendation in LDL-C measurement of

Objectives: Several pediatric advisory groups have recommended selective screening for dyslipidemia in children. Low-density lipoprotein cholesterol (LDL-C) is measured clinically with the Friedewald calculation in fasting samples. Nonfasting measurement of LDL-C would be clinically useful in children., Design and Methods: In the present study, we examine the performance of two surfactant-based direct LDL-C assays in paired samples, fasting and nonfasting, from 100 children., Results: LDL-C in the fasting state was significantly lower with the Friedewald estimation: 2.43 +/- 0. 61 mmol/L, N-geneous (Genzyme Corp.) direct LDL-C: 2.30 +/- 0.59 mmol/L, and Roche (Roche Diagnostics) direct LDL-C: 2.32 +/- 0.57 mmol/L than with ultracentrifugation-dextran-sulfate-Mg(2+) precipitation (UC-DS): 2.47 +/- 0.64 mmol/L. Moreover, there was increased negative bias using nonfasting samples with N-geneous: 2. 25 +/- 0.56 mmol/L and Roche: 2.26 +/- 0.56 mmol/L compared with fasting UC-DS. Correlation with US-DS was highest for Friedewald (r = 0.974) and fasting N-geneous (r = 0.973), and lowest with nonfasting N-geneous (r = 0.849) and Roche in fasting (r = 0.891) and nonfasting samples (r = 0.747). The sensitivity at LDL-C concentration of 2.85 mmol/L for the two direct methods when either fasting or nonfasting samples were used, was lower than that obtained with Friedewald., Conclusion: Overall, these direct LDL-C assays demonstrated limited utility in screening children but may be useful in the management of lipid disorders.

Background: Low-density lipoprotein cholesterol (LDL-C) levels are the primary basis for treatment guidelines established for hyperlipidemic children and adolescents. Levels of LDL-C are commonly monitored by means of the Friedewald formula, an indirect calculation that requires an overnight fast. A new method has been developed for the direct measurement of LDL-C (DLDL-C) that does not require fasting. We evaluated the clinical utility of this method., Design: We determined LDL-C concentrations simultaneously by the DLDL-C method, Friedewald equation, and beta-quantification (reference procedure)., Setting: Pediatric dyslipidemia clinic at Children's Hospital, Boston, Mass., Patients: Ninety-two fasting hyperlipidemic pediatric patients., Results: At the LDL-C concentration cutoffs commonly used for making therapeutic decisions, the DLDL-C method had a significant negative bias (P< or =.05) and misclassified patients into incorrect treatment groups more often than the Friedewald method. The negative predictive value for the DLDL-C method was lower than that for the Friedewald method (P< or =.05), and the cost of determining LDL-C level with the new method was 3 times greater., Conclusions: The misclassification potential for LDL-C, and the assay costs, were greater for the DLDL-C method than for the Friedewald calculation. Despite the apparent advantages of the DLDL-C method, we conclude that for hyperlipidemic children the utility of this new method is not advantageous over the conventional Friedewald method. In some conditions, such as in diabetes or marked hypertriglyceridemia, the DLDL-C method may be useful.

LDL-cholesterol (LDL-C) concentration is currently determined in most clinical laboratories by the Friedewald calculation. This approach has several limitations and may not meet the current total error requirement in LDL-C measurement of < or = 12%. We evaluated the analytical and clinical performance of the direct N-geneous LDL-C assay (Equal Diagnostics). The N-geneous method correlated highly with the modified beta-quantification assay (r = 0.95; y = 0.91x + 70.6 mg/L; n = 199), showed no significant effect of increased triglyceride or other common interferants, and performed adequately in serum samples from nonfasting individuals. This assay demonstrated a mean total error of 6.75% over a wide range of LDL-C concentrations. In addition, at the medical decision cutoff points, this LDL-C assay showed positive predictive values of 78-95% and negative predictive values of 84-99%. We conclude that the N-geneous LDL-C meets the currently established analytical performance goals and appears to have a role in the diagnosis and management of hypercholesterolemic patients.

This study examines the performance and clinical use of a commercial immunoseparation assay for low-density lipoprotein (LDL) cholesterol in a sample population of normolipidemic and hyperlipidemic adult volunteers. Using paired fasting and nonfasting samples, we compared the direct LDL assay with the beta quantification method and the Friedewald calculation. Overall, the direct LDL assay correctly classified 82% and 60% of fasting and nonfasting subjects, respectively, into National Cholesterol Education Program risk groups. The Friedewald method correctly classified 84% of subjects. The fasting direct LDL assay has comparable positive and negative predictive values to the Friedewald method, except at an LDL cholesterol of 100 mg/dl. The nonfasting direct LDL assay demonstrates unacceptable positive predictive values when LDL cholesterol decreases to the 130 to 159 and > or = 160 mg/dl categories. Overall, direct LDL assay demonstrates limitations in the nonfasting state and at the LDL cholesterol level of 100 mg/dl used for patients with established coronary heart disease.

This study compares a new latex immunoseparation method for the direct determination of plasma low-density lipoprotein cholesterol (LDL-C) with the reference procedure for LDL-C (beta-quantification) in a pediatric hyperlipidemic population. The direct LDL-C assay has a mean bias of -98 mg/L in a fasting group (n = 96) of patients (mean triglycerides 1057 +/- 720 mg/L) and a bias of +177 mg/L in a nonfasting group (n = 42, mean triglycerides 4854 +/- 5457 mg/L). The mean total analytical error calculated from our data is 13.8%. The direct LDL-C assay and the commonly used Friedewald calculation respectively classified 81% and 84% of fasting patients correctly, according to the cutoffs of 1100 and 1300 mg/L for LDL-C set by the National Cholesterol Education Program for pediatric patients. Of combined fasting and nonfasting patients, 80% were correctly classified by the direct LDL-C assay. Therefore, despite several analytical shortcomings, the direct LDL-C assay may be useful in managing hyperlipidemic children without the need for a fasting specimen.

Current recommendations of the Adult Treatment Panel and the Children and Adolescents Treatment Panel of the National Cholesterol Education Program make the concentration of low-density lipoproteins cholesterol (LDL-C) in serum the basis for the classification and treatment of hypercholesterolemia. Numerous methodologies for the determination of serum LDL-C concentrations, in research and clinical laboratories, have been described. Here, we review the principles, performance, and limitations of major current methodologies for determining LDL-C concentrations. These methods include sequential and density-gradient ultracentrifugation, chromatographic and electrophoretic techniques, and precipitation methods. In addition, the advantages and disadvantages of estimating LDL-C concentration by the Friedewald equation, the most commonly used approach in clinical laboratories, are addressed.