Chemical Pathology, University of Pretoria, Pretoria, South Africa.
Chemical Pathology, University of Pretoria, Pretoria, South Africa
J Clin Pathol. 2023 Mar;76(3):145-152. doi: 10.1136/jcp-2022-208480. Epub 2023 Jan 17.
The lipid profile is important in the risk assessment for cardiovascular disease. The lipid profile includes total cholesterol, high-density lipoprotein (HDL)-cholesterol, triglycerides (TGs) and low-density lipoprotein (LDL)-cholesterol (LDL-C). LDL-C has traditionally been calculated using the Friedewald equation (invalid with TGs greater than 4.5 mmol/L and is based on the assumption that the ratio of TG to cholesterol in very- low-density lipoprotein (VLDL) is 5 when measured in mg /dL). LDL-C can be quantified with a reference method, beta-quantification involving ultracentrifugation and this is unsuitable for routine use. Direct measurement of LDL-C was expected to provide a solution with high TGs. However, this has some challenges because of a lack of standardisation between the reagents and assays from different manufacturers as well as the additional costs. Furthermore, mild hypertriglyceridaemia also distorts direct LDL-C measurements. With the limitations of the Friedewald equation, alternatives have been derived. Newer equations include the Sampson-National Institutes of Health (NIH) equation 2 and the Martin-Hopkins equation. The Sampson-NIH2 equation was derived using beta-quantification in a population with high TG and multiple least squares regression to calculate VLDL-C, using TGs and non-HDL-C as independent variables. These data were used in a second equation to calculate LDL-C. The Sampson-NIH2 equation can be used with TGs up to 9 mmol/L. The Martin-Hopkins equation uses a 180 cell stratification of TG/non-HDL-C to determine the TG:VLDL-C ratio and can be used with TGs up to 4.5 mmol/L. Recently, an extended Martin-Hopkins equation has become available for TGs up to 9.04 mmol/L.This article discusses the best practice approach to calculating LDL-C based on the available evidence.
血脂谱对于心血管疾病的风险评估很重要。血脂谱包括总胆固醇、高密度脂蛋白（HDL）-胆固醇、甘油三酯（TGs）和低密度脂蛋白（LDL）-胆固醇（LDL-C）。传统上，LDL-C 是使用 Friedewald 方程计算的（当 TG 大于 4.5mmol/L 时无效，并且基于在 mg/dL 下测量时 VLDL 中 TG 与胆固醇的比值为 5 的假设）。LDL-C 可以通过参考方法进行定量，即涉及超速离心的β定量，这不适用于常规使用。直接测量 LDL-C 预计会提供一种解决方案，适用于高 TG。然而，由于不同制造商的试剂和测定之间缺乏标准化以及额外的成本，这存在一些挑战。此外，轻度高甘油三酯血症也会扭曲直接 LDL-C 测量。由于缺乏标准化，Friedewald 方程存在局限性，已经衍生出了替代方法。较新的方程包括 Sampson-National Institutes of Health (NIH) 方程 2 和 Martin-Hopkins 方程。Sampson-NIH2 方程是使用高 TG 人群中的β定量和多元最小二乘法回归计算 VLDL-C 推导出来的，使用 TG 和非 HDL-C 作为独立变量。这些数据用于第二个方程来计算 LDL-C。Sampson-NIH2 方程可用于 TG 高达 9mmol/L。Martin-Hopkins 方程使用 TG/非 HDL-C 的 180 细胞分层来确定 TG:VLDL-C 比值，并且可用于 TG 高达 4.5mmol/L。最近，一种扩展的 Martin-Hopkins 方程可用于高达 9.04mmol/L 的 TG。本文讨论了根据现有证据计算 LDL-C 的最佳实践方法。
