Martin's, Friedewald's and Cordova's formulas compared to LDL-C directly measured in Southern Brazil

ABSTRACT Introduction: Recently, fasting flexibility for laboratory determination of lipid profile has been recommended. When triglycerides (TG) are above 400 mg/dl, the formula proposed by Martin et al. should be used to estimate the low-density lipoprotein cholesterol (LDL-C). However, this formula has not been evaluated in our population. Objectives: We evaluated the performance of Martin’s equation for LDL-C estimation compared to Cordova & Cordova and Friedewald formulas in a population of Southern Brazil. Methods: Sampling consisted of 10,664 Brazilian individuals (5,847 women) aged 1 to 93 years, with TG, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and LDL-C directly measured. Results: Martin’s formula presented significantly higher LDL-C values in patients with TG < 300 mg/dl, underestimating values when TG > 400 mg/dl, even with negative values; and LDL-C values was also overestimated in all TC ranges, with greater standard deviation. It also presented a higher mean error in the stratified intervals, and a lower correlation coefficient. Conclusion: Martin’s equation is not accurate for estimating LDL-C in our sample, unless TG is between 300 and 400 mg/dl. We recommend using the Cordova & Cordova formula as an alternative to determine LDL-C when its direct measurement is not available, and not applying the Martin’s Formula indiscriminately to other populations before it is properly evaluated and compared with other available equations.

摘要：
引言：近年来，实验室血脂谱检测已推荐采用空腹灵活检测方案。当甘油三酯（triglycerides, TG）水平高于400 mg/dl时，应采用Martin等人提出的公式估算低密度脂蛋白胆固醇（low-density lipoprotein cholesterol, LDL-C）。但该公式尚未在我们的研究人群中开展评估。

研究目的：本研究以巴西南部人群为研究对象，对比评估Martin公式、Cordova & Cordova公式与Friedewald公式估算低密度脂蛋白胆固醇的性能。

研究方法：本研究纳入10664名巴西个体（其中女性5847名），年龄范围为1至93岁，所有受试者的甘油三酯、总胆固醇（total cholesterol, TC）、高密度脂蛋白胆固醇（high-density lipoprotein cholesterol, HDL-C）及低密度脂蛋白胆固醇均为直接测定值。

研究结果：当TG＜300 mg/dl时，Martin公式估算的LDL-C值显著偏高；当TG＞400 mg/dl时，该公式会低估LDL-C水平，甚至出现负值；同时在所有总胆固醇分层区间中，该公式均会高估LDL-C值，且标准差更大。此外，该公式在各分层区间内的平均误差更高，相关系数更低。

研究结论：在本研究队列中，Martin公式并不适用于低密度脂蛋白胆固醇的估算，仅当TG处于300~400 mg/dl区间时除外。我们建议，当无法直接测定LDL-C时，可采用Cordova & Cordova公式作为替代估算方案；且在未经过恰当评估并与其他现有公式对比前，不应将Martin公式无差别地应用于其他人群。