Fasting and Nonfasting LDL Cholesterol: To Measure or Calculate?

Abstract

Whether lipid profiles should be measured in the fasting or nonfasting state is a hot topic (1)(2). The fasting state is that used conventionally (3)(4); however, it would be much simpler for patients worldwide if a lipid profile could be taken at any time of the day, irrespective of the time since and the content of the last meal. In both the US and Europe, LDL cholesterol is currently considered the most important measurement in a lipid profile (3)(5). Direct assays for measuring LDL cholesterol are widely available and used in many laboratories; however, even if LDL cholesterol measured with a direct method gives results similar to those calculated with the Friedewald equation, it is unclear how the 2 measurements compare in predicting ischemic cardiovascular disease. In this issue of Clinical Chemistry , Mora et al. report on an evaluation of fasting LDL cholesterol concentrations calculated with the Friedewald equation vs direct measurement of fasting and nonfasting LDL cholesterol concentrations for predicting cardiovascular disease in a prospective study of 27 331 women from the Women’s Health Study (6). They also examined misclassification of individuals into the National Cholesterol Education Program risk categories (3) with direct measurement of LDL cholesterol, compared with conventional Friedewald calculation of LDL cholesterol. These topics are timely and important. In 1972, Friedewald, Levy, and Fredrickson presented a new method for estimating LDL cholesterol and compared it with the gold standard of preparative ultracentrifugation (7). The method required only the measurement of plasma total cholesterol, HDL cholesterol, and triglyceride concentrations—all of which can be measured without the use of laborious and expensive …