Validation of the Martin Method for Estimating Low-Density Lipoprotein Cholesterol Levels in Korean Adults: Findings from the Korea National Health and Nutrition Examination Survey, 2009-2011

Despite the importance of accurate assessment for low-density lipoprotein cholesterol (LDL-C), the Friedewald formula has primarily been used as a cost-effective method to estimate LDL-C when triglycerides are less than 400 mg/dL. In a recent study, an alternative to the formula was proposed to improve estimation of LDL-C. We evaluated the performance of the novel method versus the Friedewald formula using a sample of 5,642 Korean adults with LDL-C measured by an enzymatic homogeneous assay (LDL-C-D). Friedewald LDL-C (LDL-C-F) was estimated using a fixed factor of 5 for the ratio of triglycerides to very-low-density lipoprotein cholesterol (TG:VLDL-C ratio). However, the novel LDL-C (LDL-C-N) estimates were calculated using the N-strata-specific median TG:VLDL-C ratios, LDL-C-5 and LDL-C-25 from respective ratios derived from our data set, and LDL-C-180 from the 180-cell table reported by the original study. Compared with LDL-C-F, each LDL-C-N estimate exhibited a significantly higher overall concordance in the NCEP-ATP III guideline classification with LDL-C-D (p < 0.001 for each comparison). Overall concordance was 78.2% for LDL-C-F, 81.6% for LDL-C-5, 82.3% for LDL-C-25, and 82.0% for LDL-C-180. Compared to LDL-C-5, LDL-C-25 significantly but slightly improved overall concordance (p = 0.008). LDL-C-25 and LDL-C-180 provided almost the same overall concordance; however, LDL-C-180 achieved superior improvement in classifying LDL-C < 70 mg/dL compared to the other estimates. In subjects with triglycerides of 200 to 399 mg/dL, each LDL-C-N estimate showed a significantly higher concordance than that of LDL-C-F (p < 0.001 for each comparison). The novel method offers a significant improvement in LDL-C estimation when compared with the Friedewald formula. However, it requires further modification and validation considering the racial differences as well as the specific character of the applied measuring method.