Cholesterol Measurement

Knowing the amount of cholesterol in the blood is important to good health, but GAO found that it was hard to learn the correct level from a single test. Given the wide range of instruments used to test cholesterol and day-to-day variations in diet, exercise, and illness, GAO believes that persons should consider being tested several times to determine cholesterol levels. Doctors and patients need to be aware of fluctuations in cholesterol measurements and that any decision to classify and treat a patient should be based on the average of multiple measurements and an assessment of other risk factors. GAO summarized this report in testimony before Congress; see: Cholesterol Measurement: Variability in Methods and Test Results, by Kwai-Cheung Chan, Director of Program Evaluation in Physical Systems Areas, before the Subcommittee on Technology, House Committee on Science. GAO/T-PEMD-95-17, Feb. 14, 1995 (15 pages).

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.