Correlation of extended Martin/Hopkins equation with a direct homogeneous assay in assessing low‐density lipoprotein cholesterol in patients with hypertriglyceridemia

BACKGROUND: The Friedewald or Martin/Hopkins equation is widely used to estimate low‐density lipoprotein cholesterol (LDL‐C) at triglyceride (TG) levels <400 mg/dL. In this study, we aimed to validate the recently developed Sampson and extended Martin/Hopkins equations intended for use in patients with TG levels up to 800 mg/dL by comparing them to a direct homogenous assay. METHODS: In total, 8676 participants with serum TG levels <800 mg/dL were enrolled in this study. LDL‐C was directly measured using Abbott homogeneous assay (DLDL) and estimated using the Friedewald (FLDL), Martin/Hopkins (MLDL), extended Martin/Hopkins (EMLDL), and Sampson equations (SLDL). The overall concordance between the DLDL and LDL‐C estimates was calculated. The performance of the four equations was also compared using Bland–Altman plots and mean absolute difference (MAD). RESULTS: The EMLDL was more accurate than other LDL‐C equations particularly for patients with TG≥400 mg/dL (MAD = 10.43; vs. FLDL: MAD = 21.1; vs. SLDL: MAD 11.62). The overall concordance of FLDL, MLDL, EMLDL, and SLDL with DLDL in TG values ranging from 200 to 799 mg/dL were 52.2, 70.5, 71.6, and 65.7%, respectively (p < 0.001), demonstrating the EMLDL as the most optimal estimation method, particularly for high TG levels (≥200 mg/dL). CONCLUSION: Both the original and extended Martin/Hopkins method are optimal in estimating LDL‐C levels in clinical laboratories using the Abbott analyzer in patients with TG levels of 200–399 and 400–799 mg/dL, respectively. Meanwhile, caution is need that considerable underestimation of Friedewald and Sampson equation could lead to undertreatment in hypertriglyceridemia.