Accuracy of the One Touch II whole blood glucose analyzer when used by analysts with diverse technical backgrounds.

BACKGROUND: The accuracy of hand-held analytical systems is dependent on the complexity of the instrument and the technical skills of the tester. We evaluated the analytical performance of the LifeScan One Touch II glucose analyzer when used by persons with various levels of technical skill and experience. METHODS: A medical technologist conducted tests on three One Touch II systems to ensure that the units were functioning properly. The technologist then trained six analysts (a physician, a registered nurse, a licensed practical nurse, a physician assistant, and two patients) in the proper use of the glucose analyzer. RESULTS: In the hands of a medical technologist, the precision of the three glucose analyzers tested was from 1.0% to 1.9% coefficient of variation (CV) and from 2.3% to 4.2% CV for the low- and high-quality control materials, respectively. The day-to-day precision (5-day period) was from 2.1% to 3.6% CV, and from 3.5% to 4.1% CV for the low- and high-quality control materials, respectively. Comparisons of the glucose values (n = 40 fresh patient serum samples) with a reference method yielded a correlation coefficient of 0.992 to 0.993, and an overall bias of -7%. Although the values obtained by the six operators were statistically different, the differences were not clinically relevant. CONCLUSIONS: Our data suggest that the One Touch II glucose analyzer is a reliable system, and that its function is not dependent on the technical skills of the operator.

Matrix effects on proficiency testing materials. Impact on accuracy of cholesterol measurement in laboratories in the nation's largest hospital system.

The objective of this collaborative study with the Department of Veterans Affairs (VA), College of American Pathologists (CAP), and the Centers for Disease Control and Prevention (CDC) was to quantitate the matrix-induced biases of cholesterol measurements on the CAP Comprehensive Chemistry Surveys materials used in proficiency testing (PT). A total of 174 VA Medical Centers outpatient clinics and clinical laboratories participate in the VA-CDC National Cholesterol Standardization and Certification Program. This study was conducted in 112 VA laboratories that have been standardized for measuring cholesterol accurately (within +/- 3.0% of the CDC reference-method values) using fresh, unfrozen, unadulterated human serum samples. Fresh serum samples and 1990 CAP Surveys materials were sent by overnight mail, and the laboratories were asked to analyze them simultaneously in triplicate in a single analytic batch run. The results showed significant matrix-effect biases with the CAP Surveys materials with six of the eight major peer groups, despite the fact that accuracy of cholesterol measurements was maintained with fresh serum samples. The magnitude and direction (positive or negative) of the matrix-effect biases were instrument, reagent, and method specific using the following peer groups: du Pont Dimension (-8.9%); Beckman CX4, CX5, and CX7 (-5.5%); Kodak Ektachem 400, 500, and 700 (+4.4%); Instrumentation Laboratory Monarch (-3.1%); Baxter Paramax (-2.4%); Technicon SMAC and RA (+1.3%); Hitachi/BMD 704 through 747 (+0.4%); and Abbott Spectrum (-0.3%). The CAP PT materials used currently do not behave in a manner identical to fresh human serum when measuring cholesterol on many, but not all, analytic systems. The observed biases due to "matrix effects" with PT materials will cause incorrect conclusions about the accuracy of many laboratory procedures performed on fresh patient specimens. This matrix-effect phenomenon will severely hamper interlaboratory accuracy transfer, standardization efforts, and monitoring performance of a laboratory's testing accuracy with the use of the current survey materials used in PT programs. Collaborative efforts are needed to (1) improve PT fluids to analytically behave more like fresh, human serum; (2) improve instrument design and reagent formulation; and (3) select methods and methodologic parameters that are more "robust" and less sensitive to the exact character of processed calibrators, quality control, and PT materials.

Accurate measurement of serum total cholesterol: the need for standardization.

Heightened awareness of the importance of cholesterol and heart disease has increased cholesterol testing in the United States. The demand for reliable cholesterol measurements has become a focal concern of the patient as well as the clinician. This paper covers the major analytical and preanalytical issues and factors that can affect the reliability of cholesterol results. We discuss factors that lead to impression and inaccuracy; solutions for some of the major problems; resources and techniques to help standardize cholesterol measurement; and preanalytical issues that can affect cholesterol results--i.e., patient preparation; collection, processing, storage and proper analysis of the specimen; biological and seasonal variations; age and gender; diet; alcohol consumption; weight changes; exercise; primary diseases; and infections and trauma. Many of these can be controlled by the physician, resulting in more reliable cholesterol readings under stable metabolic conditions. Accurate values will help to classify the patient's coronary heart disease risk, define appropriate treatment strategies, and simplify monitoring of dietary and/or drug intervention.

Interlaboratory comparison of glycohemoglobin results: College of American Pathologists Survey data.

We describe recent changes in the College of American Pathologists Glycohemoglobin (gHb) Survey, made to improve the assessment of interlaboratory variability and the accuracy of results reported. The questionnaire portion of the survey was revised to include an updated list of current methods, and results for survey specimens were grouped according to the component measured (Hb A1, Hb A1c, or total gHb). The survey specimen material was changed to a material thought to give more reliable results with all available methods. After these changes, instituted in 1989, between-laboratory CVs decreased for some methods. Furthermore, gHb values between method types were more consistent with results obtained from fresh blood samples under very controlled laboratory conditions. However, these recent data also show that the interlaboratory variability is still quite high for some methods and that the variability within and between method types is still very great. We describe a pilot standardization program for gHb measurement.

Progress in lipid reporting practices and reliability of blood cholesterol measurement in clinical laboratories in Nebraska. Efforts to align results with the Centers for Disease Control, and feasibility of meeting National Cholesterol Education Program Guidelines.

The National Cholesterol Education Program has recommended that all laboratories be consistent, precise, and accurate in the reporting and measurement of blood cholesterol levels. In a follow-up to a 1984 survey study, we assessed the changes in reporting procedures for measurements of blood lipid levels in 16 clinical laboratories in Nebraska. Using human serum reference materials of known cholesterol concentrations provided by the Centers for Disease Control, we also assessed the precision and accuracy of measurement of blood cholesterol levels in clinical laboratories in Nebraska. Fourteen of the 16 laboratories restudied in 1987 had altered the reference range for total serum cholesterol since 1984, 86% of whom lowered the upper limit of the reference range. Eleven of 16 laboratories expressed reference ranges for total serum cholesterol in terms of patient age in 1987, while only 7 of 20 did in 1984. Gender-based reference ranges increased from 0 to 5 from 1984 to 1987. Similar trends were seen in the reporting of high-density lipoprotein cholesterol and triglyceride concentrations. Reporting procedures varied greatly; only 1 laboratory used National Cholesterol Education Program risk levels for measuring total serum cholesterol levels. Fifteen laboratories met the National Cholesterol Education Program recommendation for precision (coefficient of variation, less than or equal to 5%) and 78% of laboratories obtained results that satisfied the current recommendation for accuracy (within 5% of "true value," as determined by the Centers for Disease Control).

Dietary influences on cardiovascular disease risk in anabolic steroid-using and nonusing bodybuilders.

Recent studies have described an association between high-risk lipoprotein profiles and anabolic steroid abuse by athletes. However, none have included a comprehensive evaluation of diet as a confounding variable. The risk of cardiovascular disease (CVD) and its associations with drug abuse, dietary patterns, and training regimens were evaluated in 18 steroid-using (SU) and 17 non-steroid-using (NSU; no history of drug use or greater than or equal to 1 year drug-free) male bodybuilders. CVD risk was also evaluated in 10 control males. Fasting serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL) and HDL subfractions 2 and 3, low-density (LDL) and very-low-density (VLDL) lipoprotein cholesterol, apoproteins (APO) A-1 and B, and triglycerides (TG) were analyzed at baseline (greater than or equal to 6 months drug-free) and the peak of steroid self-administration in SU. NSU were tested at similar times. Baseline CVD risk factor ratios (TC/HDL) were elevated (greater than 4.97) in 44% of SU and 24% of NSU. When baseline LDL and HDL values were compared to National Cholesterol Education Program CVD risk guidelines, these percentages stayed the same. At the peak of steroid administration significant changes were observed in LDL (22% increase), HDL (63% decrease), HDL-2 (86% decrease), HDL-3 (54% decrease), and TC/HDL (85% increase). No similar measures were observed among NSU or controls. Diets of all bodybuilders were similar, and included a daily intake of 5739 (+/- 2500) kcal, 324 (+/- 163) g protein, 637 (+/- 259) g carbohydrate, 214 (+/- 109) g fat, 5 (+/- 8) g alcohol, 1413 (+/- 1151) mg cholesterol, and a P/S ratio of 0.6 (+/- 0.3). Significant relationships between dietary fats and serum lipids were observed in the NSU. Polyunsaturated fatty acids were correlated with TG and VLDL (r = 0.69; p = 0.01), and TC/HDL (r = 0.06; p = 0.04). Total fats were correlated with TG (r = 0.57; p = 0.05), HDL-3 (r = -0.62; p = 0.04), and VLDL (r = 0.57; p = 0.05), and saturated fats with HDL-3 (r = -0.59; p = 0.055). Diet was moderately associated with lipoproteins in SU, but steroids had a much greater influence on CVD risk. Despite disease promoting diets NSU had relatively average CVD risk that may be attributed to protective effects of rigorous training.

The need for accurate total cholesterol measurement. Recommended analytical goals, current state of reliability, and guidelines for better determinations.

We have approached a dawn of a new era in detection, evaluation, treatment, and monitoring of individuals with elevated blood cholesterol levels who are at increased risk for CHD. The NHLBI's National Cholesterol Education Program will be the major force underlying this national awareness program, which is dependent on the clinical laboratories providing reliable data. Precision or reproducibility of results is not a problem for most of the laboratories, but accuracy is a major concern. Both the manufacturers and laboratorians need to standardize the measurement for cholesterol so that the accuracy base is traceable to the NCCLS NRS/CHOL. The manufacturers need to adopt a uniform policy that will ensure that the values assigned to calibration, quality control, and quality assurance or survey materials are accurate and traceable to the NCCLS/CHOL. Since, at present, there are some limitations of these materials caused by matrix effects, laboratories are encouraged to use the CDC-NHLBI National Reference Laboratory Network to evaluate and monitor their ability to measure patient blood cholesterol levels accurately. Major areas of analytical problems are identified and general, as well as specific, recommendations are provided to help ensure reliable measurement of cholesterol in patient specimens.

New guidelines and recommendations on the detection, evaluation, and treatment of patients with undesirable cholesterol levels.

To help reduce the prevalence of elevated blood cholesterol levels in adult Americans, the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH) launched the National Cholesterol Education Program (NCEP) in 1985. The program aims to raise awareness and understanding about high blood cholesterol levels as a risk for coronary artery disease (CAD) and the benefits of lowering cholesterol levels as a means of preventing CAD. This national awareness program is aimed at three target groups: (1) health professions, (2) the public and patient, and (3) the community. This article summarizes the highlights of the NHLBI NCEP Laboratory Standardization Panel's (LSP) report and the Adult Treatment Panel's (ATP) report. The LSP report emphasized the need for accurate and precise cholesterol measurements and evaluated the current state of reliability of these measurements. It also described the degree to which accurate and precise cholesterol measurements are possible based on currently available instrumentation, reagents, and methods. The LSP report made a series of broad recommendations designed to improve laboratory performance that are discussed in this article. The ATP's report established criteria that define candidates with high blood cholesterol levels who should receive medical intervention and provided guidelines on how to detect, set goals, treat, and monitor these patients over time. For the first time in medical history there is a consensus by leading experts in the field on the measurement, detection, and treatment of patients with hypercholesterolemia. The detailed recommendations of the LSP and ATP should have a major impact on 40 million adults in the United States and may save approximately 300,000 lives annually.

Reliability of lipid, lipoprotein, and apolipoprotein measurements.

The National Heart, Lung, and Blood Institute national awareness program on cholesterol and heart disease has placed new demands on laboratorians to utilize and perform more reliable measurements of lipids, lipoproteins, and apolipoproteins. The general public's awareness and the clinicians' concerns about the reliability of laboratory testing make it paramount that the analytical problems and issues are identified and solutions are provided to increase the current state of reliability of the measurement of these blood constituents. To accomplish this, the initial step is to assess the current state of reliability of lipid, lipoprotein, and apolipoprotein measurements in the clinical laboratories. Accuracy and precision of measurements of total cholesterol, triglycerides, high-density lipoprotein cholesterol, and apolipoproteins A-I and B are extensively discussed, and general as well as some specific recommendations are provided for some of the apparent problems.

Lipoprotein disorder, cirrhosis, and olivopontocerebellar degeneration in two siblings.

Two siblings had olivopontocerebellar degeneration, failure to thrive, hepatic fatty change and cirrhosis, and a dyslipoproteinemia characterized by low cholesterol and elevated triglycerides. This condition was distinct from other cerebellar atrophies and ataxias and was not due to malabsorption or malnutrition. Cerebellar degeneration progressed rapidly during the first year of life, and both children died from intercurrent infections and surgical complications at 11 and 17 months. Stereotyped clinical and pathologic findings in the two patients suggest a previously unreported genetic metabolic disorder affecting the liver and the CNS.

Accuracy of participant results utilized as target values in the CAP Chemistry Survey Program.

Samples of lyophilized human serum were circulated to more than 7,000 participants in the College of American Pathologists chemistry survey program. The participants measured the concentrations of glucose, cholesterol, uric acid, and urea along with other constituents in the samples. Selected samples also were sent to the National Bureau of Standards (NBS) for analysis of these same analytes by definitive methods. Consensus mean values of participant results are used as target values. The participant values were compared with the NBS values, providing a measure of the accuracy of the designated target values. There was, in general, excellent correlation between the NBS definitive values and the designated target values. These target values can provide reliable reference points by which to evaluate participant performance.

Urinary magnesium loss in aging diabetic mellitus rats.

Past studies on urinary loss of magnesium (Mg) have focused on young diabetic rats. The aims of the present study were to determine the rapidity at which glycosuria and magnesuria occur after the induction of diabetes mellitus (DM) in old male rats, and the maximal amount of Mg and glucose (Glu) loss in the urine and whether or not the loss is persistent and (3) the most sensitive means of correlating the Mg and Glu loss in the urine. Three methods of expressing urinary Mg and Glu concentrations were selected: Method A: mg/24 h; Method B: mg/24 h/kg body weight (BW), and Method C: ratio of Mg to creatinine (Mg/Crea) or ratio of Glu to Crea (Glu/Crea). Our study indicated a maximal and rapid loss of Mg and Glu occurring within 1 week after induction of DM (by streptozotocin injection) and remained in effect for 6 weeks, the end of the study. The urinary Mg loss due to DM correlated best with urinary Glu when expressed as mg/24 h/kg BW. In addition, the increase in urinary Mg concentration paralleled the degree of glycosuria and reached a maximum of 5-12 times baseline values when expressed by Method B. This was 4-10 times when expressed by Method A, and 2-6 times when expressed by Method C. Since polyuria is a feature of DM, we also correlated the relationship between these two factors, and found a significantly positive correlation (r = 0.735) particularly when Mg was expressed as mg/24 h. In summary, rapid and significant urinary Mg loss is observed in old rats made diabetic with streptozotocin.(ABSTRACT TRUNCATED AT 250 WORDS)