Testing cholesterol accuracy. Performance of several common laboratory instruments.
The national emphasis on assessing coronary risk by cholesterol testing mandates that analytical determinations be as accurate and precise as is medically necessary. One goal of the National Cholesterol Education Program is to improve the quality of laboratory tests. Currently, 5% limits of imprecision and 5% of bias vs the nationally accepted Abell-Kendall reference method is recommended, with a goal of reducing these limits to 3% by 1992. Clinicians must be aware of how the cholesterol values are obtained, and especially whether the laboratory's method meets the performance goals. We assayed patients' serum samples for cholesterol using several commercially available, routinely used enzymatic methods and by the Abell-Kendall reference method. Precision of these methods was also assessed using serum-based controls. All instruments were operated precisely according to the manufacturers' instructions. Performance was objectively judged based on the National Cholesterol Education Program goals and on medically allowable total error. In all cases, the DuPont aca, the Kodak Ektachem, the Hitachi 737, and the Cobas FARA determined cholesterol levels acceptably. The precision and accuracy goals of 3% are achievable by these methods.