Abstract Introduction Low-density lipoprotein cholesterol (LDL) levels are usually calculated using the Friedewald (F) equation, although the Martin-Hopkins (MH) equation has been proposed as a more accurate alternative. The difference between the application of one or the other could have clinical relevance in patients with very high cardiovascular risk, such as those admitted for acute coronary syndrome (ACS). Purpose Our aim was to assess the discordance between F and MH to calculate the estimated LDL lowering ratio (LRLDL) needed to reach the target 55mg/dL in patients hospitalised with ACS and to compare the LRLDL calculated from F and MH with a direct measurement (DM) of LDL in a subgroup of patients. Methods Observational, single-centre study of a cohort of 563 consecutive patients admitted for ACS with triglycerides 400 mg/dL. Lipid profile was determined on admission and LDL was calculated by using F and MH equations. In a subgroup of 84 patients, DM LDL (enzymatic colorimetry) was performed. The difference between LDL estimated by each method and 55 mg/dL was used to calculate LRLDL. The difference in LRLDL between methods was calculated and discordance was considered when it was 6% (LDL decrease expected when doubling the statin dose). Results In the overall population of 563 patients, the median LRLDL according to F was 44. 4% 29. 5-57. 0; while by MH it was 46. 9% 32. 8-58. 0, with a strong positive correlation (r=0. 974; p0. 001). 68 cases (12. 1%) were identified with discordance between F and MH (table), which was associated with low LDL and elevated triglyceride levels. In the 84 patients with DM, the median LRLDL was 49. 5% 33. 9-58. 3, with a strong positive correlation between LRLDL obtained with DM and that calculated with both F and MH (0. 961 and 0. 975, respectively; p0. 001). However, there was discordance between LRLDL obtained with DM and calculated with F and/or MH in 15 patients (17. 8%), and it was associated with elevated triglyceride levels (OR 1. 017; CI95% 1. 009-1. 026; p0. 001). As illustrated by the Bland Altman plots (figure), the discordance was due to underestimation of calculated LRLDL in all but two cases. The discordance rate was higher with F (23. 8%) than with MH (10. 7%), p0. 001; and the magnitude of the difference in discordant cases was also higher with F than with MH (8. 4% vs 2. 5%, p0. 001), with respect to the LRLDL obtained with DM. Conclusions Despite the good correlation in the estimation of LRLDL using the F and MH equations, clinically relevant discordance exists in approximately one in eight patients admitted for ACS. In most cases of discordance, the MH equation is more accurate when compared to DM, especially in patients with elevated triglyceride levels. In these circumstances, in patients hospitalised with ACS, the use of MH to estimate LRLDL would be particularly advisable. Table. Figure.
Hernandez et al. (Sat,) studied this question.