| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Measurement of bile acid synthesis in man by release of 14CO2 from 26-14Ccholesterol: comparison to isotope dilution and assessment of optimum cholesterol specific activity Mitchell, J. C., B. G. Stone, et al. (1992), Lipids 27(1): 68-71. Abstract: Bile acid synthesis can be measured as release of 14CO2 from 26-14Ccholesterol divided by cholesterol specific activity, but this method has not been validated in human subjects. We made twelve comparisons of this CO2 method to standard isotope dilution in six normal subjects and found a mean discrepancy of 6%. Linear regression analysis of one value with respect to the other revealed a correlation coefficient of 0.83 (P less than 0.01), a Y-intercept close to zero (-4.98) and a slope close to 1 (1.06), suggesting good correspondence between the two methods. To assess the potential for error arising from use of serum cholesterol to estimate specific activity of cholesterol used for bile acid synthesis, we compared synthesis measured using serum free cholesterol specific activity to that measured using bile cholesterol specific activity, which is known to be near isotopic equilibrium with the precursor pool used for bile acid synthesis. Synthesis calculated in these two ways differed by less than 10%. The data indicate that the CO2 method using either serum or bile cholesterol specific activity provides a valid estimate of bile acid synthesis in man. |
| Measurement of blood cholesterol, decentralized, using a Reflotron, or centralized in a laboratory. A comparison Christensen, T. E., E. Agner, et al. (1990), Ugeskr Laeger 152(45): 3346-8. Abstract: In connection with an extensive screening programme for blood cholesterol, the cholesterol values in 105 participants were measured on a sample of capillary blood employing a Reflotron and, simultaneously, samples of venous blood were examined by conventional enzymatic analysis in a laboratory. Whereas the day-to-day variation and the scatter involved were quite limited in the laboratory, the variation scatter between the two methods of measurement was 0.65 mmol/l. This figure was, however, no greater than that described between different laboratories in USA. Nevertheless, it is an important problem with the Reflotron method that even slight deviations from the recommended procedure of withdrawing blood involve a systematic risk for erroneously low cholesterol results. |
| Measurement of capillary cholesterol as an aid to the management of hypertensive patients with hyperlipidaemia--an assessment of the Reflotron Curzio, J. L., E. Farish, et al. (1992), J Hum Hypertens 6(3): 185-8. Abstract: The Reflotron dry chemistry method of capillary cholesterol measurement has been widely adopted as a rapid means of population screening. We attempted to use it to monitor changes in cholesterol in a trial of intensive dietary intervention in hyperlipidaemic hypertensives. Four hundred and eighty-nine capillary cholesterol levels measured by the Reflotron were compared with levels for venous samples obtained simultaneously and assayed by the Biochemistry Department using conventional laboratory methods. The mean difference between them was 0.3 mmol/l +/- 0.8 (SD). Approximately one-third of the variability in the difference between the two methods was explained by the variables, Reflotron machine used and time (R2 = 54%, adjusted R2 = 34%). We conclude that the Reflotron is not suitable for accurate assessment of the modest changes in cholesterol which occur in individual patients during dietary intervention. |
| Measurement of capillary cholesterol in hyperlipidemia Curzio, J. L., C. Howie, et al. (1991), Br J Gen Pract 41(351): 433. |
| Measurement of cholesterol and other lipoprotein constituents in the clinical laboratory Warnick, G. R. (2000), Clin Chem Lab Med 38(4): 287-300. Abstract: Measurements of lipids and lipoproteins in the clinical laboratory have become increasingly important because of their predictive association with cardiovascular diseases, especially coronary artery disease. The US National Institutes of Health-sponsored National Cholesterol Education Program and counterparts in other countries have developed national consensus guidelines for diagnosis and treatment of coronary artery disease which provide risk cut-points and define use of the lipid/lipoprotein analytes in case finding and therapy. Total and low density lipoprotein cholesterol and triglycerides are measured as positive risk factors and high density lipoprotein cholesterol as an inverse risk factor for coronary artery disease. A National Cholesterol Education Program-sponsored expert laboratory panel has developed guidelines for measurements with requisite analytical performance targets for total error and corresponding precision and bias. The US Centers for Disease Control and Prevention have established reference methods for total and high density lipoprotein cholesterol and for triglycerides, with a method for low density lipoprotein cholesterol in development. Standardization programs for research laboratories and a Cholesterol Reference Method Laboratory Network for diagnostic manufacturers and clinical laboratories provide reliable access and documentation of traceability to accepted reference methods. Methods for the lipid/lipoprotein analytes have improved dramatically in recent years and, coupled with improved chemistry analyzer systems and more attention to standardization by manufacturers, offer considerable improvement in analytical performance. Fully automated homogeneous assays for high density lipoprotein cholesterol and newer similar assays for low-density lipoprotein cholesterol have potential for better precision as well as more convenient and cost-effective measurements. Attention to pre-analytical sources of variation is also important in making reliable classification of patients. |
| Measurement of cholesterol and triglycerides in dried serum and the effect of storage Ramakrishnan, L., K. S. Reddy, et al. (2001), Clin Chem 47(6): 1113-5. |
| Measurement of cholesterol gallstone growth in vitro van Den Berg, A. A., J. D. van Buul, et al. (2000), J Lipid Res 41(2): 189-94. Abstract: Methods to study growth of gallstones in the laboratory have not been reported. We here present such a method. Human cholesterol gallstones were harvested from patients with multiple nearly identical stones. The gallstones were washed and added to supersaturated model biles and the formation of cholesterol crystals and the increases in mass of human cholesterol gallstones were studied concurrently, over a period of weeks, using nephelometry and a microbalance, respectively. All stones incubated in model biles supersaturated with cholesterol increased in mass. Increases in the degree of supersaturation of cholesterol in the model biles resulted in increased growth of stones. The mass increases, the growth rates, and the spatial orientation of accreted crystalline cholesterol differed among various stone types. The kinetics and structures of stone growth were similar when the stones were incubated in supersaturated, native, human gallbladder biles. The structure of accreted cholesterol was the same as found on the surface of some human gallstones that were harvested during apparent active growth in situ. This simple method allows accurate measurements of stone growth in vitro, in patterns that mimic stone growth in vivo, and is useful for studies on the relationships of gallstone growth and the kinetics of cholesterol crystallization. |
| Measurement of cholesterol in capillary blood using the Reflotron system. Results from approximately 1,000 comparisons with reference measurements of cholesterol in venous serum Gerdes, L. U., A. M. Bak, et al. (1990), Ugeskr Laeger 152(24): 1739-43. Abstract: The results of 969 measurements of total cholesterol in capillary blood from fingerstick, performed with the Reflotron-system in the field, were compared with measurements of total cholesterol in venous serum. The comparison allows an evaluation of the combined effect of differences in sample material, working place, stability of methods and staff training. The mean values for all measurement were nearly identical with the two methods, and approximately 95% of the Reflotron-measurements were within an interval of +/- 0.7 mmol/l around the estimated true value. However, values below approximately 6 mmol/l were systematically underestimated, and values above approximately 7 mmol/l were overestimated with the Reflotron-system. The coefficient of variation of the system is below 5%, but both this precision and the accuracy appear to be unstable. Evaluated as a tool in screening for hypercholesterolemia, measurements with the system resulted in a modest extent of erroneous classification of subjects, but the positive diagnostic predictive value of the statement "cholesterol above 7 mmol/l" is only approximately 76%. Simulations of likely variations in the accuracy and precision of the method show a significant influence on the extent of errors. It is recommended that measurements with the system are routinely controlled by measuring an appropriate control material, at the start of each run and after every 30 samples. |
| Measurement of cholesterol in membranes Ahmed, H. A. (1993), Methods Mol Biol 19: 179-82. |
| Measurement of cholesterol in plasma and other body fluids Warnick, G. R. and A. T. Remaley (2001), Curr Atheroscler Rep 3(5): 404-11. Abstract: Measurement of cholesterol has become increasingly important with recognition of its predictive association with cardiovascular diseases. Government and professional groups in the United States and other countries have developed consensus guidelines for using cholesterol and the lipoproteins in identifying patients at risk and in managing therapies. Accuracy in the measurements is essential not only for reliable classification of patients, but also in public health/wellness programs and in research. Laboratory experts have developed requisite analytical performance targets and guidelines for measurements. Manufacturers of diagnostic reagents and laboratories can assure accuracy by accessing the Cholesterol Reference Method Laboratory Network, which offers reference methods for total, high-density lipoprotein, and low-density lipoprotein cholesterol. Recommendations for controlling pre-analytical sources of variation and uniform interpretation of patient results facilitate reliable classification of patients. Driven by increasing workloads and the need for increased efficiency in laboratory testing, dramatic improvements have been made in recent years in automating laboratory analyzers, as well as the methods used for lipoprotein analysis. Newer technology allows multiple sequential measurements in the same cuvette, as well as point-of-care measurements, using strip tests and compact analyzers. Efforts continue to develop reliable, minimally invasive tests in body fluids other than serum. |
| Measurement of cholesterol of major serum lipoprotein classes by anion-exchange HPLC with perchlorate ion-containing eluent Hirowatari, Y., H. Yoshida, et al. (2003), J Lipid Res 44(7): 1404-12. Abstract: We have developed a high-performance liquid chromatography (HPLC) method for measurement of cholesterol in the major classes of serum lipoproteins, i.e., HDL, LDL, IDL, VLDL, and chylomicrons. Lipoproteins in serum were separated on a column containing diethylaminoethyl-ligand nonporous polymer-based gel by elution with a step gradient of sodium perchlorate concentration, and detected by post-column reaction with a reagent containing cholesterol esterase and cholesterol oxidase. The within-day assay and between-day assay coefficients of variation for cholesterol concentration in lipoproteins were in the ranges of 0.9-6.4% and 1.1-11.9%, respectively. The correlation coefficients between the values of HDL, LDL, IDL, VLDL, and chylomicron cholesterol measured by the HPLC method and those estimated by an ultracentrifugation method were 0.892, 0.921, 0.840, 0.930, and 0.873, respectively. Values of remnant-like particle cholesterol measured by an immunoseparation technique (Japan Immunoresearch Laboratories, Japan) were significantly correlated with VLDL and chylomicron cholesterol values measured by the HPLC method (r = 0.883 and r = 0.729, respectively).This rapid and accurate HPLC method was successfully applied to the analysis of plasma lipoproteins of patients with hyperlipidemia. |
| Measurement of endogenous synthesis of plasma cholesterol in rats and humans using MIDA Neese, R. A., D. Faix, et al. (1993), Am J Physiol 264(1 Pt 1): E136-47. Abstract: We used the mass isotopomer distribution analysis (MIDA) technique to measure endogenous synthesis of plasma cholesterol in vivo in rats and normal human subjects. Sodium 1-13C- or 2-13Cacetate was infused, and plasma free cholesterol was analyzed by gas chromatography-mass spectrometry. Frequencies of mass isotopomers M0-M4 (mass-to-charge ratio 368-372) were quantified. The enrichment of the true precursor for cholesterol synthesis (acetyl-coenzyme A in contributing tissues) was determined using the MIDA method. This technique remains mathematically valid even if more than one tissue contributes to circulating free cholesterol. The fractional contribution (f) from endogenous synthesis to free cholesterol in normal women (n = 5) was 2.48 +/- 0.39% after 7 h in the postabsorptive state and 1.27 +/- 0.41% after 8 h of refeeding. In ad libitum-fed rats (n = 12), f was 2.89 +/- 0.44% after 12 h, whereas administration of recombinant tumor necrosis factor increased this value fourfold. Next, the rate constant (k) for removal of labeled free cholesterol from plasma was calculated. Higher masses (M2-M4) were followed to avoid the problem of persistent label incorporation. During the 60 h after cessation of 13Cacetate infusions, k was 0.02490 +/- 0.00298/h in humans. Using these values of k and f, absolute cholesterogenesis was 568 +/- 55 mg/day in normal women (follicular menstrual phase), similar to prior estimates based on whole body sterol balances. Women also exhibited a diurnal variation for endogenous cholesterol synthesis (34.6 +/- 5.4 mg/h nighttime vs. 15.9 +/- 5.2 mg/h daytime) consistent with current knowledge about rhythms in cholesterogenesis. Checks on the model were internally consistent (e.g., comparisons among different isotopomers for calculating precursor enrichment). We conclude that fractional and absolute endogenous cholesterol synthesis can be measured using stable isotopes in vivo by the MIDA technique. |
| Measurement of fractional esterification rate of cholesterol in plasma depleted of apoprotein B containing lipoprotein: methods and normal values Dobiasova, M. and J. Frohlich (1996), Physiol Res 45(1): 65-73. Abstract: The distribution of differently sized HDL particles in the plasma can be assessed by measurement of the fractional rate of cholesterol esterification (FERHDL). We have characterized the isotopic assay and compared it to the enzymatic measurement of the decrease in HDL free cholesterol (mass assay). The normal values of FERHDL were established in 116 apparently healthy individuals. The isotopic assay is particularly sensitive to changes in the incubation temperature above 37 degrees C. The reproducibility of the assay in aliquots of plasma stored at -20 degrees C and -70 degrees C for 3 months and even up to 2 years was high. Intraindividual variability of FERHDL is low. In the subjects in whom FERHDL was measured over a 3-month and 2-5 years' period, FERHDL showed a low variability (97.5 +/- 2.6% and 101 +/- 6.0% respectively in a paired t-test). Comparison of the isotopic assay and the mass assay revealed that the isotopic assay was much more reproducible. Normal values of FERHDL and the HDL subspecies distribution (using gradient gel electrophoresis) were established in 63 men and 56 women. The average values of FERHDL were significantly higher in men (16.8 +/- 4.5%/h) than in women (10.6 +/- 3.6%/h) and correlated well with the distribution of the HDL subspecies. FERHDL radioassay as a highly reproducible method for the assessment of HDL subspecies distribution which may be suitable for both retrospective and prospective studies of diseases of atherogenous origin. |
| Measurement of HDL cholesterol Grubits, J. (1992), J R Soc Med 85(8): 509. |
| Measurement of in vivo cholesterol synthesis from 2H2O: a rapid procedure for the isolation, combustion, and isotopic assay of erythrocyte cholesterol Wong, W. W., D. L. Hachey, et al. (1991), J Lipid Res 32(6): 1049-56. Abstract: A rapid preparative scale purification of erythrocyte free cholesterol has been developed for measurements of in vivo cholesterol synthesis from 2H2O. The quantity and purity of cholesterol obtained is suitable for combustion, zinc reduction of the water formed, and determination of deuterium isotopic content by gas isotope ratio mass spectrometry. The ability to detect and to quantitate a range of cholesterol synthesis rates is illustrated by measurements on young pigs receiving diets without and with added dietary cholesterol. |
| Measurement of intestinal cholesterol absorption by plasma and fecal dual-isotope ratio, mass balance, and lymph fistula methods in the mouse: an analysis of direct versus indirect methodologies Wang, D. Q. and M. C. Carey (2003), J Lipid Res 44(5): 1042-59. Abstract: The rate of intestinal cholesterol (Ch) absorption is an important criterion for quantitation of Ch homeostasis. However, studies in the literature suggest that percent Ch absorption, measured usually by a fecal dual-isotope ratio method, spans a wide range, from 20% to 90%, in healthy inbred mice on a chow diet. In the present study, we adapted four standard methods, one direct (lymph collection) and three indirect (plasma and fecal dual-isotope ratio, and sterol balance) measurements of Ch absorption and applied them to mice. Our data establish that all methodologies can be valid in mice, with all methods supporting the concept that gallstone-susceptible C57L mice absorb significantly more Ch (37 +/- 5%) than gallstone-resistant AKR mice (24 +/- 4%). We ascertained that sources of error in the literature leading to marked differences in Ch absorption efficiencies between laboratories relate to a number of technical factors, most notably expertise in mouse surgery, complete solubilization and delivery of radioisotopes, appropriate collection periods for plasma and fecal samples, and total extraction of radioisotopes from feces. We find that all methods provide excellent interexperimental agreement, and the ranges obtained challenge previously held beliefs regarding the spread of intestinal Ch absorption efficiencies in mice. The approaches documented herein provide quantifiable methodologies for exploring genetic mechanisms of Ch absorption, and for investigating the assembly and secretion of chylomicrons, as well as intestinal lipoprotein metabolism in mice. |
| Measurement of low-density-lipoprotein cholesterol in serum: a status report Rifai, N., G. R. Warnick, et al. (1992), Clin Chem 38(1): 150-60. Abstract: Current recommendations of the Adult Treatment Panel and the Children and Adolescents Treatment Panel of the National Cholesterol Education Program make the concentration of low-density lipoproteins cholesterol (LDL-C) in serum the basis for the classification and treatment of hypercholesterolemia. Numerous methodologies for the determination of serum LDL-C concentrations, in research and clinical laboratories, have been described. Here, we review the principles, performance, and limitations of major current methodologies for determining LDL-C concentrations. These methods include sequential and density-gradient ultracentrifugation, chromatographic and electrophoretic techniques, and precipitation methods. In addition, the advantages and disadvantages of estimating LDL-C concentration by the Friedewald equation, the most commonly used approach in clinical laboratories, are addressed. |
| Measurement of plasma LDL cholesterol in patients with diabetes Whiting, M. J., M. D. Shephard, et al. (1997), Diabetes Care 20(1): 12-4. Abstract: OBJECTIVE: To assess the accuracy of plasma LDL cholesterol concentrations estimated by the Friedewald formula and a direct immunoseparation method by comparison with a reference ultracentrifugation procedure in patients with diabetes. RESEARCH DESIGN AND METHODS: Fasting plasma samples with triglyceride concentrations < 4.5 mmol/l were collected from 100 patients with diabetes (28 type I and 72 type II) and LDL cholesterol concentrations were compared by the three methods. RESULTS: LDL cholesterol values determined by the reference beta-quantitation procedure were highly correlated with both the Friedewald formula (r = 0.96) and a direct immunoseparation method (r = 0.92). Calculated (Friedewald) LDL cholesterol coincided with the reference method with < 10% error in 74% of the total diabetic group (82% of type I and 68% of type II diabetic patients). However, agreement between the direct LDL cholesterol and reference methods was significantly less (P = 0.02), with only 44% of patients having an error of < 10% (52% of type I and 41% of type II diabetic patients). The direct immunoseparation method for LDL cholesterol showed a positive bias with increasing triglyceride concentrations, particularly for patients with type II diabetes. CONCLUSIONS: In the group of diabetic patients studied with plasma triglyceride concentrations < 4.5 mmol/l, the Friedewald formula provided an accurate estimation of LDL cholesterol. The direct immunoseparation method significantly overestimated LDL cholesterol at triglyceride levels between 2 and 4.5 mmol/l. |
| Measurement of pleural fluid cholesterol and lactate dehydrogenase. A simple and accurate set of indicators for separating exudates from transudates Costa, M., T. Quiroga, et al. (1995), Chest 108(5): 1260-3. Abstract: OBJECTIVES: To evaluate the usefulness of diverse combinations of pleural cholesterol concentration, pleural or serum protein, and lactate dehydrogenase (LDH) levels for the differentiation of pleural exudates and transudates. DESIGN: Prospective laboratory study of pleural effusions. SETTING: Medical school hospital. PATIENTS: One hundred eighty consecutive internal medicine ward patients in whom the etiologic diagnosis of their pleural effusion was confirmed. MEASUREMENTS: Cholesterol concentration in pleural fluid and protein and LDH both in pleural fluid and blood serum. RESULTS: According to their etiology, 49 (27.2%) of the effusions were transudates and 131 (72.7%) were exudates. Using a cutoff point of 45 mg for pleural cholesterol and values for protein and LDH of Light et al, the best diagnostic power corresponded to the combination of pleural cholesterol and LDH: cholesterol level over 45 mg/dL and/or LDH over 200 IU/L identified exudates with a sensitivity of 99% and a specificity of 98%. All the other combinations showed inferior values and the criteria of Light et al reached 98 and 82%, respectively. CONCLUSIONS: The measurement of pleural cholesterol and LDH permits the separation of pleural exudates from transudates with an accuracy similar to the original report of Light et al, with the advantage of requiring only two laboratory determinations and no simultaneous blood sample. |
| Measurement of pleural fluid cholesterol levels Cruz, E., T. Quiroga, et al. (1997), Chest 111(2): 525-6. |