Cholesterol

Serum total cholesterol is a combination of high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and very low-density lipoprotein (VLDL) cholesterol. High serum total cholesterol is a risk factor for cardiovascular disease (see “Prediction of Coronary Heart Disease Using Risk Factor Categories.” In its first report (1988) on high blood cholesterol, the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults provided guidelines for the treatment of high blood cholesterol, defined as a serum total cholesterol value greater than or equal to 240 mg/dL (6.20 mmol/L). This definition was also used in the panel’s second and third reports. A more recent set of guidelines—the result of initial efforts by the National Heart, Lung, and Blood Institute and subsequent efforts by the American College of Cardiology and the American Heart Association—focused on which groups of people could benefit from statin use based on their risk factors. For more information on the current cholesterol guidelines, see “Management of Blood Cholesterol in Adults: Systematic Evidence Review From the Cholesterol Expert Panel” and “AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APHA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.”

While the current cholesterol guidelines focus on clinical assessments to manage blood cholesterol for individuals, Health, United States focuses on presenting population-level estimates using the broad indicators identified in earlier guidance based on measured serum total cholesterol level and the reported use of cholesterol-lowering medications. Cholesterol levels are determined using the National Health and Nutritional Examination Surveys (NHANES) T_CHOL file. The three measures of total cholesterol that are presented are the following: hypercholesterolemia, high serum total cholesterol, and mean serum total cholesterol. Hypercholesterolemia is based on both laboratory testing and self-reported use of cholesterol-lowering medication. It is defined as measured serum total cholesterol greater than or equal to 240 mg/dL (6.20 mmol/L) or reporting taking cholesterol-lowering medications. Respondents who were told by a doctor or health professional that their cholesterol was high, were told by a doctor to take cholesterol-lowering medication, and who answered “yes” to the question, “Are you now following this advice to take prescribed medicine?” were classified as taking cholesterol-lowering medication. High serum total cholesterol is defined as measured serum total cholesterol greater than or equal to 240 mg/dL (6.20 mmol/L). Both high serum total cholesterol and mean serum total cholesterol are based on serum samples collected during the NHANES examination.

As part of the NHANES examination, venous blood serum samples collected from NHANES participants at mobile examination centers (MEC) were frozen and shipped on dry ice to the laboratory conducting the lipid analyses. Serum total cholesterol was measured on all examined adults regardless of whether they had fasted, and data were analyzed regardless of fasting status. Cholesterol measurements are standardized according to the criteria of the Centers for Disease Control and Prevention (CDC)—and later the CDC–National Heart, Lung, and Blood Institute Lipids Standardization Program—to ensure comparable and accurate measurements. For more information, see: Myers GL, Cooper GR, Winn CL, Smith SJ. The Centers for Disease Control–National Heart, Lung, and Blood Institute Lipid Standardization Program: An approach to accurate and precise lipid measurements. Clin Lab Med 9(1):105–35. 1989. A detailed summary of the procedures used for measurement of total cholesterol in earlier NHANES years has been published in: Carroll MD, Kit BK, Lacher DA, Shero ST, Mussolino ME. Trends in lipids and lipoproteins in US adults, 1988–2010. JAMA 308(15):1545–54. 2012. A description of the laboratory procedures for the total cholesterol measurement for different NHANES years is published by the National Center for Health Statistics on the NHANES website.