When Obtaining Lipid Measurements, Is Fasting Always Necessary?
Measuring lipids has become an essential component of patients' risk for cardiometabolic disorders. The 2013 American College of Cardiology/American Heart Association (ACC/AHA) Guideline on the Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults1 broadened the focus beyond the role of low-density lipid cholesterol (LDL-C) to screening for more encompassing global risk factors. Today, lipid panels are used to screen for familial lipid disorders, clarifying a diagnosis of metabolic syndrome, assessing residual risk in a treated patient, diagnosing and treating patients with suspected hypertriglyceridemic pancreatitis and diagnosing hypertriglyceridemia. Traditionally, lipid tests have been conducted under fasting conditions2 but the disorders for which these screening tests are used are not uniform, and it may not be necessary to insist on a fasting test for all of them.
A recent article by Driver et al examines the circumstances that determine whether obtaining fasting lipid measurements is really necessary.2 The authors frame this decision around several key questions.
Question 1: What is the initial risk for my untreated primary prevention patient?
The authors note that the purpose of lowering LDL-C in primary prevention is to reduce the risk of a first heart attack or stroke. Higher LDL-C levels are associated with higher rates of both cardiovascular and all-cause mortality. The authors cite a study by Doran et al3 that utilized 10-year data from a cohort enrolled in NHANES-III, who were stratified on the basis of fasting or non-fasting status and followed for a mean of 14 years. The study found that non-fasting LDL-C has prognostic value similar to that of fasting LDL-C. Doran and colleagues recommended that “national and international agencies should consider reevaluating the recommendation that patients fast before obtaining a lipid panel.”3
While risk estimators, including the Systematic Coronary Risk Evaluation, Framingham Score, Reynolds Risk Score, QRISK2, and Atherosclerotic Cardiovascular Disease (ASCVD) Pooled Cohort Risk Estimator, which include measurement of total cholesterol, were generally developed using scores obtained under fasting conditions, they actually vary little between fasting and non-fasting states. “Therefore, for risk estimation alone, either fasting or non-fasting lipids suffice,” the authors concluded.