Standardization of lipid, lipoprotein, and apolipoprotein measurements.

Accurate laboratory measurement of serum cholesterol has become a national public health priority. National proficiency testing surveys indicate that laboratory inaccuracy in cholesterol testing is more of a problem than precision. Like precision, accuracy is a function of multiple pre-analytical and analytical sources of variation. Controlling pre-analytical sources of variation helps minimize such sources of variation as intraperson biological, behavioral, and clinical differences, and variations caused by sample collection, handling, and shipping. Standardization of analytical sources of variation helps to achieve and maintain desirable analytical performance, accurate reporting, and correct interpretation of a reported cholesterol result. The intraperson total variation in lipoproteins and their constituents is of primary interest when one is interpreting a single result or a series of results from a single person. The mean of multiple specimens from the same person is required if one is to obtain an accurate value for intraperson total cholesterol and minimize pre-analytical sources of variation. Standardizing analytical sources of variation in some instrument systems requires standardizing results by using "fresh" patients' specimens.