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Evaluation of Seven Cholestech LDX AnalyzersEvaluation of Seven Cholestech LDX Analyzers
Evaluation of Seven Cholestech LDX Analyzers
for Total Cholesterol Determinations
Reprinted from CLINICAL (CHEMlSTRY, 3Y, 860 (lY93).
Copyright 1993 by the American Association of Clinical Chemistry and reprinted by permission of the copyright owner
CLIN. CHEM. 39/5, 860 864 (1993) Evaluation of Seven Cholestech LDX Analyzers for Total Cholesterol Determinations
Eugene J. Rogers1, Lorraine Misner1, Ira S2. Ockene, and Robent J. Nicolosi1,3
We assessed the performance of seven Cholestech LDX lipid analyzers under tightly controlled laboratory conditions for accuracy and precision in accordance with analytical guidelines of the National Cholesterol Education Program (NCEP). Venous heparinized whole blood (VB) and plasma (VP), venous serum (VS), and caplilary fingerstick whole blood (FB) were collected from 18 individuals. Total cholesterol (TC) concentration was measured in VB, VP, and VS on all seven instruments. Three instruments were used for TC measurements of FB. Reference cholesterol values for each individual were generated in the same laboratory with a standardized method. The within-run coefficients of variation (CVs) for all instruments with a Level I pool (1560 mg/L, n = 10) ranged from 1.3% to 1.8% (mean = 1.59%). The between-run CVs with the same pool ranged from 2.2% to 3.4% (mean = 2.84%, n = 10). Correlation coefficients derived from comparison of total cholesterol values generated by the instruments for each specimen type vs the reference cholesterol values were all >0.97. The average bias for all instruments for each sample type was 1.9% (FB), 4.3% (VB), 6.6% (VP), and 7.0% (VS). Predicted cholesterol concentration for each sample type from regression curves for total cholesterol at the suggested NCEP clinical decision cutoff values of 2000 and 2400 mg/L, respectively, were 2049 and 2431 mg/L for FB, 2081 and 2469 mg/L for VB, 2122 and 2522 mg/L for VP, and 2121 and 2521 mg/L for VS.
Indexing Terms: near - patient testing analytical performance
The proportional relation between a decrease in blood cholesterol concentration and reduced risk of coronary artery disease has been well established in several studies (1-4). In response to such findings, the National Heart, Lung, and Blood Institute (NHLBI) initiated the National Cholesterol Education Program (NCEP) (5), in which guidelines were provided to implement programs with the goal of decreasing the incidence of hypercholesterolemia and thus coronary artery disease risk. 4 Recommendations were established to clinically classify individuals (6) by various degrees of cholesterolemia.
1 Department of Clinical Laboratory Sciences, University of Massachusetts LoweU, Wilder St.—Weed HaU, Lowell, MA 01854.
2 Division of Cardiovascular Medicine, Department of Medicine, University of Massachusetts Medical Center, Worcester, MA 01655.
3 Address correspondence to this author.
4 Nonstandard abbreviations: NCEP, National Cholesterol Education Program; VB, venous whole blood; VP, venous plasma; VS, venous serum; FB, capillary fingerstick whole blood; TC, total cholesterol; and CDC, Centers for Disease Control.
Received June 1, 1992; accepted November 20, 1992
Appropriate recommendations for further evaluation and treatment were suggested in accordance with classification criteria. This program, as well as an increased public awareness concerning cholesterol, has led to massive public screening programs (7) to identify individuals at risk for the development of heart disease. The Laboratory Standardization panel of the NCEP also outlined the analytical performance requirements for measurement of serum cholesterol with the final goals for accuracy and precision set at = 3.0% (8). These requirements leave instrument manufacturers the difficult task of designing and producing cholesterol screening analyzers that are small, portable, rugged, fast, easy to use, and reliable.
In the present study we evaluated the performance of seven Cholestech LDX cholesterol analyzers (Cholestech Corp., Hayward, CA) for the measurement of total cholesterol (TC). We conducted the evaluations in a highly controlled laboratory environment, using the recommended 1992 accuracy and precision goals of <3.0% suggested by the NCEP. Measurement of total cholesterol was performed on four types of samples obtained from each individual in the study. These specimens were heparinized venous whole blood (VB) and plasma (VP), venous serum (VS), and heparinized capillary fingerstick whole blood (FB). Results obtained for each type of specimen were compared with reference values generated on VS samples by methodology certified for this measurement by the Centers for Disease Control (CDC) Lipid Standardization Program.
Materials and Methods
Seven Cholestech LDX lipid analyzers were evaluated for TC measurement over a 2-day period. The instrument evaluation protocol was designed to minimize variables in a tightly controlled environment. The instruments were positioned adjacent to each other in a laboratory and were evaluated essentially simultaneously. Manufacturer-calibrated disposable reagent "cassettes" for the Cholestech instruments were stored and used according to the instructions provided. The manufacturer states that TC concentrations can be determined in capillary or venous whole blood, serum, or plasma. FB specimens would be the choice in alternative settings such as the physician's office. The instruments are also capable of measuring high-density lipoprotein cholesterol and triglycerides, but were not evaluated for these determinations.