In 1985, NIH’s National Heart, Lung, and Blood Institute (NHLBI) initiated the National Cholesterol Education Program (NCEP), which has undertaken a major effort to encourage individuals to measure, track, and reduce their cholesterol levels (notably total and low-density lipoprotein (LDL) cholestrol) with the objective of reducing mortality and morbidity from coronary heart disease. How is cholesterol measured? 2. 3. What factors influence cholesterol levels? 4. What is the potential effect of uncertain measurement? No national data are available on the number of laboratories that conduct cholesterol tests, the number of cholesterol testing devices in use in laboratories, or the number of such tests that are done each year. HCFA survey and certification officials and NCEP have expressed concern that cholesterol testing in physicians’ offices or screening settings may differ from that done in clinical and research settings. The Accuracy of Cholesterol Measurements

In this chapter, we answer the second evaluation question: What is known about the accuracy and precision of cholesterol measurement techniques? The discussion first focuses on national accuracy goals and efforts to standardize cholesterol measures. Matrix problems can make it impossible to assign a target value to quality control material that will apply to all routine testing methods. Table 3.1 lists the 37 instrument and reagent systems and calibration bias relative to the reference method. Other factors—diet, exercise, alcohol intake—appear to have differing effects on individuals’ cholesterol levels. Laboratory Factors

How a blood specimen is collected and handled may affect lipid levels. Addressing Measurement Error

Progress has been made in improving analytical accuracy in cholesterol measurement, with the development of better methods and materials in recent years. Even if one could be certain that a laboratory could provide reasonably accurate and precise test results, biological and behavioral factors such as diet, excercise, or illness cause an individual’s cholesterol level to vary. It has been estimated that such factors may account for up to 65 percent of the total variation in an individual’s reported cholesterol measurement. For the purposes of this analysis, which is intended to illustrate the potential range of variability around an actual or known cholesterol level, we used the current goals for total analytical error (+8.9 percent for total cholesterol according to NCEP and +30 percent for HDL according to HCFA) and what is currently known about biological variability from a synthesis of studies (6.1 percent for total cholesterol and 7.4 percent for HDL cholesterol).
Why GAO Did This Study

Pursuant to a congressional request, GAO reviewed the National Heart, Lung, and Blood Institute's National Cholesterol Education Program (NCEP), focusing on the: (1) different techniques for measuring cholesterol in laboratory settings; (2) accuracy of these measurement techniques; (3) factors that influence individual cholesterol levels; and (4) potential effect of cholesterol measurement variability.

What GAO Found

GAO found that: (1) the natural daily variation in cholesterol levels and instrument measurement errors make it impossible to pinpoint individual cholesterol levels; (2) over 160 different devices with different technologies and chemical formulations are available to perform cholesterol tests; (3) standard cholesterol tests measure two cholesterol components, total cholesterol, and a related blood fat; (4) research, clinical, and hospital laboratories tend to produce reasonably accurate and precise cholesterol measurements, but little is known about cholesterol measurements in other settings such as physicians' offices and public health screenings; (5) two federal agencies have developed reference methods and quality control testing materials for manufacturers and laboratories to use in assessing their equipment's performance; (6) although cholesterol measurement methods have improved in recent years, there is a large variance in the accuracy and precision of tests performed across a broad range of devices and analytical settings; (7) there has been no overall evaluation of the different instruments and technologies laboratories use to conduct cholesterol tests; (8) biological and behavioral factors, many of which are uncontrollable, cause individual cholesterol levels to vary and may account for up to 65 percent of total variation in individual cholesterol levels; (9) the methods for collecting and handling blood specimens affect cholesterol measurements; and (10) uncertain cholesterol measurements can affect individual diagnoses and treatment decisions.