Anwar Muhammad, Khan Dilshad Ahmed, Khan Farooq Ahmad
Department of Chemical Pathology and Endocrinology, Armed Forces Institute of Pathology (AFIP), Rawalpindi.
J Coll Physicians Surg Pak. 2014 Jan;24(1):8-12.
To compare the Friedewald and modified Friedewald formulae with direct homogeneous assay for serum lowdensity lipoprotein cholesterol (LDL-C) levels estimation.
Cross-sectional study.
Armed Forces Institute of Pathology, Rawalpindi, from June to December 2011.
Healthy subjects of either gender, from Rawalpindi, aged 18-75 years were included by consecutive sampling. Patients with diabetes mellitus, chronic liver disease, chronic kidney disease, those taking lipid lowering drugs and samples with triglyceride (TG) > 4.52 mmol/l were excluded from the study. Total cholesterol, high-density lipoprotein cholesterol, TG and LDL-C were measured on Hitachi 912 chemistry analyzer (Roche). LDL-C levels were also calculated by Friedewald formula (FF) and Vujovic modified formula (VMF). Paired sample t-test and scatter plots were used for statistical analysis.
Although both calculated methods showed good correlation with direct assay (r > 0.93) in 300 subjects, but the difference was statistically significant. The ffLDL-C were 0.12 ± 31 mmol/l (p < 0.001) lower and vmfLDL-C were 0.11 ± 26 mmol/l (p < 0.001) higher than dLDL-C. The difference was not significant between ffLDL-C and dLDL-C at TG levels < 1.70 mmol/l (p = 0.58) and between vmfLDL-C and dLDL-C at TG levels 2.26 - 4.52 mmol/l (p = 0.38). At all other TG levels, the difference between LDL-C calculated by both formulas and dLDL-C was statistically significant (p < 0.001). As compared to direct assay, 11% and 14% subjects were classified in wrong National Cholesterol Education Programm's cardiac risk categories by FF and VMF respectively.
LDL-C should be measured by direct homogeneous assay in routine clinical laboratories, as the calculated methods did not have a uniform performance for LDL-C estimation at different TG levels.
比较Friedewald公式和改良Friedewald公式与直接匀相测定法估算血清低密度脂蛋白胆固醇（LDL-C）水平的差异。
横断面研究。
2011年6月至12月，拉瓦尔品第武装部队病理研究所。
通过连续抽样纳入来自拉瓦尔品第、年龄在18 - 75岁的健康受试者，男女不限。排除患有糖尿病、慢性肝病、慢性肾病的患者，正在服用降脂药物的患者以及甘油三酯（TG）> 4.52 mmol/l的样本。在日立912化学分析仪（罗氏）上测定总胆固醇、高密度脂蛋白胆固醇、TG和LDL-C。LDL-C水平也通过Friedewald公式（FF）和武约维奇改良公式（VMF）计算。采用配对样本t检验和散点图进行统计分析。
在300名受试者中，尽管两种计算方法与直接测定法均显示出良好的相关性（r > 0.93），但差异具有统计学意义。与直接测定的LDL-C（dLDL-C）相比，FF计算的LDL-C（ffLDL-C）低0.12 ± 31 mmol/l（p < 0.001），VMF计算的LDL-C（vmfLDL-C）高0.11 ± 26 mmol/l（p < 0.001）。在TG水平< 1.70 mmol/l时，ffLDL-C与dLDL-C之间的差异不显著（p = 0.58）；在TG水平为2.26 - 4.52 mmol/l时，vmfLDL-C与dLDL-C之间的差异不显著（p = 0.38）。在所有其他TG水平下，两种公式计算的LDL-C与dLDL-C之间的差异均具有统计学意义（p < 0.001）。与直接测定法相比，分别有11%和14%的受试者通过FF和VMF被错误分类到美国国家胆固醇教育计划的心脏风险类别中。
在常规临床实验室中，应采用直接匀相测定法测量LDL-C，因为计算方法在不同TG水平下对LDL-C的估算表现并不一致。
