血清LDL-C直接法测定值与间接换算值的偏差

目的 观察直接法测定血清低密度脂蛋白胆固醇(LDL-C)的含量与其间接换算值的偏差.方法 血脂测定方法按照标准化的要求进行.LDL-C用直接法测定和根据Friedewald公式换算,收集586例被检者血脂水平.结果 在三酰甘油(TG)低于400 mg/dl (4.52 mmo/L)的血样中,直接法测定LDL-C的水平基本高于其间接换算值,偏差的范围为-59 mg/dl(-0.67 mmol/L) ～ 48 mg/dl (0.54 mmol/L),差值的均值为 15.47 mg/dl (0.17 mmol/L)(P＜0.001).结论 LDL-C含量直接测定与间接换算存在偏差,检测LDL-C含量需注意方法的偏差,建议采用统一的方法.     

Planella公式与Friedewald公式计算LDL-C的比较

目的评价Planella公武计算LDL-C在临床应用的可行性.方法将Planella公式与Friedewald公式计算LDL-C进行比较,并分析其线性范围、准确度和干扰因素.结果Planella公式法计算LDL-C与Friedewald公式法计算LDL-C相关性良好,Y=1.032X+0.216,r=0.974.LDL-C浓度性在353mmol/L范围内线性良好,r=0.989 LDL-C浓度两组低中高值血清样本(0.79,1.48,2.87,1.06,1.82,2.94mmol/L)的批内和批间CV值分别为4.16%,2.92%,3.10%和6.14%,5.27%,6.01%;浓度为10.58mmol/L的TG对Planella公式计算LDL-C并不影响.结论Planella公式计算LDL-C精密度高,又不受TG的影响,结果比Friedewald公式计算LDL-C准确.     

血脂相关指标测定方法的比较研究

目的对比研究肝素抗凝、方法选择等因素对血脂指标测定值的影响。方法⑴随机抽样体检者130人,采血后离心分离血浆(肝素抗凝)和血清。按试剂盒方法(直接法),分别测定两组的甘油三酯(TG),总胆固醇(TC),低密度脂蛋白胆固醇(LDL-C),高密度脂蛋白胆固醇(HDL-C),载脂蛋白A(ApoA),载脂蛋白B(ApoB)等指标,并对两组差异进行统计性分析。⑵随机抽样心血管患者320人,按直接法测定血清TG,TC,LDL-C,HDLC,ApoA,ApoB等指标。将患者分为TG<1.5mmol/L(n=170),1.5≤TG<2.5mmol/L(n=96),2.5≤TG<3.5mmol/L(n=29),3.5≤TG<4.5mmol/L(n=10),TG≥4.5mmol/L(n=15)等5组,根据Friedewald、Planella公式,分别计算两组的LDL-C值,并与直接法比较统计学差异。结果⑴血浆、血清测定指标中,TG分别为2.63±2.03mmol/L,2.56±2.06mmol/L,P<0.05;TC,LDL-C,HDLC,ApoA,ApoB相互比较,P>0.05。⑵Friedewald公式所得的5组LDL-C值与直接法比较,P<0.01;Planella公式所得的5组LDL-C值与直接法比较,P>0.1,P<0.01,P<0.002,P<0.01,P>0.05。结论直接法测定TC,LDL-C,HDLC,ApoA,ApoB时,可用肝素抗凝的血浆替代血清,但直接法测定TG及公式法计算LDL-C时不能替代;Friedewald、Planella公式计算LDL-C误差较大,TG<1.5mmol/L时可采用Planella公式,TG>1.5mmol/L时建议采用直接法。     

血清低密度脂蛋白胆固醇公式计算法与匀相测定法结果比较

目的对匀相直接测定法测定血清低密度脂蛋白胆固醇(LDL-C)与Martin公式计算法的结果进行对比观察。方法在Olympus AU 5800型全自动生化分析仪上对790份标本直接测定胆固醇、三酰甘油(TG)、高密度脂蛋白胆固醇、LDL-C,同时运用Martin公式计算出每份标本的LDL-C,按TG1.13 mmol/L、1.13~2.25mmol/L、2.25~3.39mmol/L、3.39~4.52mmol/L、4.52mmol/L分为5组进行统计分析。结果匀相直接测定法与公式法呈良好的正相关,除TG4.52 mmol/L组外,两种方法结果差异均有统计学意义(P0.05)。两种方法在LDL-C为3.37~4.14mmol/L,4.14mmol/L时表现为较好的符合率,在LDL-C3.37mmol/L时符合率较差。结论两种方法测定结果存在偏差,血清LDL-C的公式计算值高于匀相测定值,建议对于以治疗和监测心血管病为目的患者最好采用直接测定法。     

LDL-C直接测定法与公式Friedewald计算法比较评估

目的 直接匀相测定法与Friedewald公式计算法同时测定继发性血脂紊乱患者低密度脂蛋白胆固醇(LDL-C),两方法间结果的差异进行比较评估分析.方法 收集2009～2010年垫江县人民医院门诊及住院病人中继发性血脂紊乱患者标本,分别采用直接匀相测定法和公式Friedewald计算法进行LDL-C测定.结果 Friedewald公式计算法和直接匀相测定法检测三酰甘油(TG)高于4.52 mmol/L,2.26～4.52 mmol/L和1.72～2.25 mmol/L,<1.71 mmol/L标本的LDL-C,两法测得结果的相关系数分别为0.592,0.717,0.803和0.901,且当TG<1.71 mmol/L时,公式计算法和直接匀相测定法测得的LDL-C经pearson相关性检验,具有显著相关(P<0.05).结论 在继发性血脂紊乱患者中,当TG<1.71 mmol/L时,可采用Friedewald公式法计算LDL-C,当TG≥1.71 mmol/L时,宜按标准化的要求采用直接匀相测定法测定LDL-C.     

对Friedewald公式法计算低密度脂蛋白胆固醇结果的可靠性评估

目的比较由匀相测定法与Friedewald公式法计算得到的低密度脂蛋白胆固醇（LDL-C）值的差异,评估两者在临床应用中的相关性及可能出现的偏差。方法选择1 180例门诊及住院患者,测定空腹血清LDL-C、高密度脂蛋白胆固醇（HDL-C）、总胆固醇（TC）、三酰甘油（TG）水平,以匀相测定法为对比方法,计算法为实验方法,计算相关系数（r）和直线回归方程,对两者之间的预期偏差进行评估;并以实测值为参考值,计算在不同浓度范围LDL-C计算值与实测值的符合率、计算值在给定医学决定水平处的阳性预测值和阴性预测值。结果2种方法的r〉0.97（P〈0.001）,在不同医学决定水平预期偏差均在其可信区间上限与下限之间;以实测值为参考值,多数情况下计算值与实测值的符合率〉85%,仅在3.12-3.64 mmol/L之间,两者符合率较低;在不同医学决定水平,计算值具有较高的阴性预测值（〉98%）和阳性预测值（85%）,仅在3.64 mmol/L处,阳性预测值较低（77.8%）。结论计算法与测定法有良好的相关性,计算法的预期偏差在可接受范围内。在不同的医学决定水平,计算法能较好地区分“阴性”和“阳性”样本,对于实测值在3.12-3.64 mmol/L之间的样本,计算法可能较高地估计了LDL-C的浓度。     

肾病综合征血脂和载脂蛋白变化及临床意义

目的了解肾病综合征(NS)患者血脂和载脂蛋白的变化及其对疾病转归的影响。方法用日立7060型全自动化分析仪测定血清胆固醇(CHO)(CHOD-PAP法)、甘油三酯(TG)(GPO-POD法)、载脂蛋白A(ApoA)和载脂蛋白B(ApoB)(免疫比浊法)、高密度脂蛋白胆固醇(HDL-C)(直接一步法)、低密度脂蛋白胆固醇(LDL-C)(按Friedewald公式计算)。结果241例肾综合患者血清CHO、TG、ApoA、ApoB、HDL-C和LDL-C水平较158例正常对照组显著升高。在给予激素和降脂治疗后,肾综患者血清CHO、TG、ApoB和LDL-C水平逐步下降,ApoA和HDL-C有一定程度的升高。结论提示临床上应注意对肾综患者血脂蛋白水平变化的监控,有助于对肾综的诊断及预后的判断,其血脂和载脂蛋白可作为辅助诊断肾综的生化指标。     

公式计算法测定血清低密度脂蛋白胆固醇比较

血清低密度脂蛋白胆固醇 (LDL -C)是血脂分析的常规项目 ,血清LDL -C水平与动脉粥样硬化、冠心病的发生率成正相关 ,通常以高LDL -C作为冠心病的首要致病因素。测定血清LDL -C的方法有分离低密度脂蛋白测定其中胆固醇含量法如化学和免疫沉淀法等 ,以及不需分离、直接可以进行自动化分析的均相一步法测定。Friedewald公式 (简称F公式 )计算法是一般实验室的常规方法 ,但F公式准确性受甘油三酯 (TG)水平影响。Planella等[1] 报道一种根据载脂蛋白B(apoB)、总胆固醇 (TC)、TG、估算LDL -C的新公式 ,其不受高TG血症影响 ,可以准确…     

低密度脂蛋白胆固醇假性降低1例分析

低密度脂蛋白胆固醇(LDL-C)常用来评价和监测高胆固醇血症,是动脉粥样硬化发生发展的重要脂类指标。传统的方法是应用Friedewald公式[LDL-C=(TC)-(HDL-C)-(TG/2.2)mmol/L]来确定低密度脂蛋白胆固醇的量,但其易受高甘油三酯(TG)的影响。而LDL-C直接测定法具有简便、快速的优点,灵敏度好,特异性高,不受高TG的影响,是较之公式法更好的测定LDL-     

不同检测系统结果在血脂达标切点判断中的临床差异分析及解决方案

目的比较3种血脂检测系统结果的差异, 分析其对血脂管理中危险分层及临床决策的影响, 并寻找减小影响的方法。方法在2022年8—10月中南大学湘雅二医院体检者及住院患者中收集甘油三酯(TG)<4.5 mmol/L的血清样本196份, 分别用日立-和光(HW)、罗氏、迈瑞3种系统直接检测TG、总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C), 并由公式(TC-HDL-C)计算非高密度脂蛋白胆固醇(非HDL-C)以及根据Friedewald公式计算LDL-C(F-LDL-C), 进行方法学对比。分别计算这6个指标在3种检测系统间的变异系数(CV), 评价结果的一致性, 用Pearson相关系数评价各指标在不同系统间的相关性。根据《中国血脂管理指南》推荐的不同危险分层LDL-C的达标值将样本分成<1.4、1.4～<1.8、1.8～<2.6、2.6～<3.4和≥3.4 mmol/L组, 统计不同系统LDL-C检测结果分在同一组的样本数及百分率, 评估系统间LDL-C差异对血脂管理临床决策的影响。通过2种方法计算校正因子:(1)用E...     

Validation of the Friedewald formula for the determination of low-density lipoprotein cholesterol compared with beta-quantification in a large population

Lipoprotein data from 9477 subjects, covering a wide range of total plasma cholesterol levels, were used to examine the validity of the Friedewald formula for estimating plasma concentrations of low-density lipoprotein cholesterol (LDL-C) using high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) concentrations. Values of LDL-C obtained from the Friedewald formula were compared with values of LDL-C derived from preparative ultracentrifugation used as a reference method. We found that the bias associated with the Friedewald formula was not related to plasma LDL-C levels and was smaller than −4.0% even for plasma LDL-C values <3.0 mmol/l. Moreover, in the subgroup of individuals with plasma TG levels ≤4.5 mmol/l, the Friedewald formula underestimated LDL-C levels with a bias between −3.1% and −1.9% according to TG quartiles. Interestingly, the Friedewald formula showed no significant bias in patients with plasma TG levels between 4.51 and 8.82 mmol/l, suggesting that the calculated LDL-C are reliable and could be clinically useful in patients with plasma TG levels higher than 4.5 mmol/l which is the reference cut-point value used by most clinical laboratories. Finally, multiple regression analyses showed that the very low-density lipoprotein cholesterol (VLDL-C)/TG ratio represented nearly 63% (P < 0.0001) of the variance of the bias associated with the Friedewald formula. We concluded that the Friedewald formula may be reliable at low LDL-C levels and at TG levels up to 9 mmol/l but may be used with caution when the VLDL-C/TG ratio is high as observed in patients with type III dysbetalipoproteinemia.     

Comparing a novel equation for calculating low-density lipoprotein cholesterol with the Friedewald equation: A VOYAGER analysis

Treating elevated low-density lipoprotein cholesterol (LDL-C) to risk-stratified target levels is recommended in several guidelines. Thus, accurate estimation of LDL-C is required. LDL-C is typically calculated using the Friedewald equation: (total cholesterol) – (non-high-density lipoprotein cholesterol [non-HDL-C]) – (triglycerides [TGs]/5). As the equation uses a fixed value equal to 5 as a divisor for TGs, it does not account for inter-individual variability, often resulting in underestimation of risk and potentially undertreatment. It is specifically inapplicable in patients with fasting triglycerides ≥400 mg/dL. A novel method of LDL-C calculation was derived and validated by Martin et al.: (non-HDL-C) – (triglycerides/adjustable factor). This equation uses an adjustable factor, the median TG:very-low-density lipoprotein cholesterol ratio in strata defined by levels of TG and non-HDLC, as divisor for TGs, and the adjustable factor ranging from 3 to 12 has been shown to provide more accurate estimates of LDL-C compared with the Friedewald equation using a direct assay as the gold standard.We used 70,209 baseline and on-treatment lipid values from the VOYAGER meta-analysis database to determine the difference in calculated LDL-C values using the Friedewald and novel equations. In patients with TGs <400 mg/dL, LDL-C values calculated using the novel equation were plotted against those calculated using the Friedewald equation. The novel equation generally resulted in LDL-C values greater than the Friedewald calculation, with differences increasing with decreasing LDL-C levels; 23% of individuals who reached a LDL-C target of 70 mg/dL with the Friedewald equation did not achieve this target when the novel equation was used to calculate LDL-C; these figures were 8% and 2% for <100 mg/dL and < 130 mg/dL targets, respectively. In patients with triglycerides ≥400 mg/dL, in whom the Friedewald equation is not valid, lipid values calculated using the novel equation were compared with those obtained by β-quantification. Values calculated with the novel equation did not appear to be closely related with those calculated by β-quantification in these patients. In conclusion, the novel equation provides a higher estimation of exact LDL-C values than the Friedewald equation, particularly in patients with low LDL-C levels, which may result in undertreatment of some patients whose LDL-C was calculated using the Friedewald method. However, neither may be suitable for patients with TG ≥400 mg/dL.     

Effects of total cholesterol and triglyceride on the percentage difference between the low-density lipoprotein cholesterol concentration measured directly and calculated using the Friedewald formula.

BACKGROUND: We elucidate how the triglyceride (TG) and total cholesterol (TC) concentrations affect the percentage difference (%DeltaLDL) between the low-density lipoprotein cholesterol (LDL-C) concentration evaluated by direct measurement (DLDL-C) and calculated using the Friedewald formula (FLDL-C), under conditions allowing the calculation. METHODS: Serum concentrations of TC, TG, high-density lipoprotein cholesterol (HDL-C), and DLDL-C were measured and the FLDL-C and %DeltaLDL were calculated for 38,243 Koreans who had TG values <4.52 mmol/L. The DLDL-C was measured using the homogeneous Kyowa Medex assay (Kyowa, Tokyo, Japan). The %DeltaLDL was calculated using the equation: [(FLDL-C-DLDL-C)/DLDL-C]x100. RESULTS: The mean %DeltaLDL-C was -9.1+/-6.4%. The %DeltaLDL differed by more than +/-5% in 75.4% of the subjects, and the FLDL-C was lower than the DLDL-C in 96.3%. The mean %DeltaLDL-C for the group with the highest TG and lowest TC was 11.8-fold that for the group with the lowest TG and highest TC. CONCLUSIONS: Under conditions satisfying the requirements of the Friedewald formula, the DLDL-C and FLDL-C differed significantly over the concentration ranges of both TC and TG. In an evaluation of patients with hyperlipidemia, the Friedewald calculation may underestimate the risk for coronary heart disease.     

Lipoprotein cholesterol concentrations in the plasma of human subjects as measured in the fed and fasted states

Lipoprotein cholesterol concentrations in plasma are routinely estimated by using the Friedewald formula, whereby very-low-density lipoprotein cholesterol (VLDL-C) is estimated to be one-fifth the plasma triglyceride concentration. Ordinarily, this formula is applied only to plasma sampled from patients in the fasted state. To determine whether lipoprotein cholesterol measurements are altered substantially in plasma sampled from nonfasting subjects, we obtained postprandial blood samples from 22 healthy subjects (nine men, 13 women, ages 22-79 years) fed a fat-rich meal (1 g fat per kilogram body wt.). The plasma triglyceride concentration increased postprandially in all subjects (233 +/- 16% of baseline at 3 h). The mean cholesterol concentration in plasma was essentially unchanged. High-density lipoprotein cholesterol (HDL-C) was significantly decreased (94 +/- 2% at 3 h, P less than 0.001). VLDL-C and low-density lipoprotein cholesterol (LDL-C), estimated by the Friedewald formula, were compared with measurements obtained by modified Lipid Research Clinics (LRC) methodology. As measured by either method, VLDL-C increased and LDL-C decreased significantly after the fat-rich meal. These postprandial changes were significantly greater (P less than 0.01) when estimated by the Friedewald formula than by LRC methodology. We conclude that (a) lipoprotein cholesterol concentrations measured in the fed subject differ significantly from those measured in the fasted subject, and (b) plasma must be obtained after at least a 12-h fast if an individual's risk of coronary heart disease is to be accurately assessed.     

Five methods for determining low-density lipoprotein cholesterol compared

We evaluated three precipitation methods for determination of low-density lipoprotein cholesterol in serum and an indirect method involving the Friedewald formula (Clin Chem 18: 499-502, 1972) by comparison with results by ultracentrifugation. The results of all methods for 83 sera, including 59 hyperlipidemic type IIA, IIB, and IV sera agreed very well, at least for concentrations of serum triglycerides below 8 mmol/L. The accuracy of the Friedewald formula was confirmed in 285 other sera, including 66 sera with triglycerides content between 4.52 and 8.0 mmol/L. For type III sera, the precipitation methods produced similar values to those obtained with the Friedewald formula, all being much higher than the ultracentrifugation values. Density-gradient ultracentrifugation showed that the very-low-density lipoprotein remnants in type III sera almost completely coprecipitated with the low-density lipoproteins. The precipitation methods are not only accurate but also very precise (CV less than 5%); they can therefore be used in clinical laboratories to measure atherogenic low-density lipoproteins plus the remnants of very-low-density lipoproteins. However, when serum triglycerides and high-density lipoprotein cholesterol also are determined, the Friedewald formula is a reliable alternative.     

低密度脂蛋白胆固醇保护性试剂匀相测定法的临床评价

目的 对低密度脂蛋白胆固醇(LDT-C)保护性试剂匀相测定法进行临床评价。 方法 分析了保护性试剂匀相测定法的精密度、准确性、特异性和干扰因素.并随机选取了219份病人血清标本,比较分析用保护性试剂匀相测定法直接测定与Friedewald公式和Planella公式计算的LDL—C结果。 结果 保护性试剂匀相测定法具有较好的精密度(批内、批间CV和总CV均小于3％)。线性范围至10.4mmol/L,最低检测浓度为0.08mmol/L,平均同收率为101.2％:基本不受极低密度脂蛋白(VLDL)、高密度脂蛋白(HDL)和血红蛋白的影响。在TG<4.52mmol/L时,用匀相测定法与Friedewald公式和Planella公式的计算法结果之间相关性良好,两种公式计算法结果之间的也有较好相关性;而在TG>4.52mmoL/L时,匀相测定法与两种计算法之间的相关性差。结论 保护性试剂匀相测定法简便、快速、结果准确,易于自动分析,适合在临床实验室常规检测应用。     

Estimation of LDL cholesterol based on the Friedewald formula and on apo B levels

OBJECTIVES: The plasma apolipoprotein B (apo B) concentrations have been considered to be a more accurate representation of atherogenic particles and it has been proposed that the formula LDL-C (mmol/L) = 0.41TC - 0.32TG + 1.70apo B - 0.27 is reliable for the estimation of LDL-C (Clin Chem 1997; 43: 808-15). We undertook the present study to investigate the reliability of this formula in a large number of hyperlipidemic patients. DESIGN AND METHODS: 1) The Friedewald formula (LDL-F) and the apo B-based formula (LDL-B) were compared with the beta-quantification reference procedure in 130 individuals with a wide range of total cholesterol (TC) and triglyceride (TG) levels, and 2) the LDL-C levels obtained by the Friedewald formula were compared with those calculated by the apo B-based formula in 1010 individuals attending our outpatient lipid clinic. RESULTS: The LDL-F and the LDL-B formulae for LDL-C estimation were found to be in good agreement with the beta-quantification (r = 0.96 and 0.97, respectively). The bias of each method plotted as a function of TG (up to 4.52 mmol/L) was found positive for the LDL-F, whereas the LDL-B was independent of the concentrations of TG. When a large number of individuals were examined, a good correlation between the two equations was found (n = 1010, r = 0.98). The difference between the two methods was not correlated with serum TG levels. However, it was correlated to serum TC, and apo B levels. CONCLUSIONS: The LDL-B formula is a more reliable and accurate method than the LDL-F formula, especially at TG levels >2.26 mmol/L, although it underestimates LDL-C concentrations. Furthermore, this equation can be used in hypertriglyceridemic patients (TG >4.52 mmol/L) in whom the Friedewald equation is inaccurate.     

Influence of intermediate-density lipoproteins on the accuracy of the Friedewald formula

Values of low-density lipoprotein (LDL) cholesterol (C) according to the Friedewald formula (Clin Chem 1972;18:499-502) were compared with those obtained by lipoprotein fractionation in 98 healthy subjects (control group), 135 specimens from patients with peripheral vascular and cerebrovascular disease (atherosclerotic group), and 45 with chronic renal failure on hemodialysis (CRF group). All had concentrations of total cholesterol between 3.23 and 7.76 mmol/L (1.25-3.00 g/L) and triglycerides less than 3.39 mmol/L (less than 3.00 g/L). The percentage error of calculated LDL-C was 4% in controls with a cholesterol/triglycerides (C/TG) ratio for very-low-density lipoprotein (VLDL) of 0.20, but greater than 60% in those with a (C/TG)VLDL ratio of 0.40. The percentage of error in sera of patients with atherosclerosis and chronic renal failure was higher than in controls with a similar mean (C/TG)VLDL ratio. The percentage of error of calculated LDL-C increases progressively with the increase in the C/TG intermediate-density lipoprotein (IDL) ratio, both in controls and in the atherosclerotic and CRF groups. Similar findings are observed when the mean percentage of error of measured LDL-C is evaluated. The percentage of error from calculated LDL-C in the atherosclerotic and CRF groups is significantly lower than that obtained by comparison of LDL-C separated by ultracentrifugation when the "broad cut" LDL (IDL plus LDL, both by ultracentrifugation) was used. The high percentage of errors found in the groups of patients studied underlines the need for caution when assessing the reliability of the Friedewald formula, particularly in cases in which disturbances in IDL composition are suspected.     

Marked effects of extreme levels of lipoprotein(a) on estimation of low-density lipoprotein cholesterol

Background

Low-density lipoprotein cholesterol (LDL-C) is usually calculated using the Friedewald equation. However, this calculation method does not account for the cholesterol associated with lipoprotein(a) [Lp(a)]. Using the Dahlen equation, Li et al. have shown a strong positive correlation between serum Lp(a) levels and overestimation of LDL-C levels.

Objective

To determine how the extreme levels of Lp(a) influence the LDL-C calculation.

Methods

We performed a retrospective chart review of the lipid profile and Lp(a) of 223 patients (men and women). LDL-C was calculated using the Friedewald equation. Lp(a) concentrations were measured by an ELISA. Other serum lipids were measured enzymatically by standard methodology. Corrected LDL-C was calculated using the Dahlen equation.

Results

We found that this overestimation is very significant in individuals with extreme levels of Lp(a) (mean overestimation of 40% at Lp(a) > 1200 mg/L).

Conclusions

Calculated LDL-C is markedly overestimated in patients with extreme levels of Lp(a).