Impact of fasting duration on LDL cholesterol concentrations estimated by the Friedewald, Martin-Hopkins, and Sampson/NIH equations.

Introduction: A paradigm shift is occurring in lipid testing, as fasting is no longer required. We aimed to determine whether low-density lipoprotein cholesterol (LDL-C) concentrations calculated using three different equations, along with the components used in these calculations, vary with different fasting durations in routine clinical practice.

Materials and methods: The concentrations of LDL-C were calculated using the Friedewald, Martin-Hopkins, and Sampson/NIH equations, along with the lipid components involved in these equations, depending on time since the last meal in a cohort of 77,300 outpatients at a community hospital. The study population was divided into groups according to fasting durations by 2-hour intervals. A general linear model was applied to identify differences between fasting and nonfasting groups.

Results: Regardless of the calculation method, LDL-C concentrations varied with fasting duration for up to 8-10 hours. The greatest absolute mean differences in LDL-C concentrations between fasting and nonfasting states were - 0.32, - 0.30, and - 0.26 mmol/L when using the Friedewald, Sampson/NIH, and Martin-Hopkins equations, respectively. Among the equation components, triglyceride concentrations were the most sensitive to fasting duration, remaining elevated for 4-6 hours after the last meal, while total cholesterol and non-high-density lipoprotein cholesterol (HDL-C) concentrations decreased for up to 8-10 hours postprandially. However, HDL-C concentrations remained relatively stable.

Conclusions: The variation in postprandial LDL-C concentrations was observed not to differ between the three calculation methods and reached negligible concentrations after at least 8 hours of fasting. If LDL-C concentrations measured in a nonfasting state are near clinical decision thresholds, subsequent lipid measurement should be performed in a fasting state.