Serum cholesterol determination

Srisawasdi P, Chaichanajarernkul U, Teerakranjana N, Kroll MH. Implementation of cellulomonas cholesterol oxidase for total serum cholesterol determination by the endpoint method. J Clin Lab Anal. 2008 22 50-58. 

In 1932, McEachern and Gilmour [40] investigated on an hourly basis serum cholesterol concentrations of 28 normal fasting individuals. The subjects first were given a special fat-free low-protein supper at 5 p.m. The following day at 8 a.m., 10 a.m., 11 a.m., 12 noon and 1 p.m., blood was taken from all 28 persons for their serum cholesterol determinations. A total of 140 test samples were collected, which corresponded to 5 specimens drawn over 5 different time spans, from each of the 28 test subjects. Cholesterol measurements of 140 blood samples from 28 individuals showed wide ranges of cholesterol values in every set of five blood samples. In order for the reader to appreciate the full extent of cholesterol level variations reported in the article, we have prepared a tabulation. Table I shows the serum cholesterol concentrations of 4 selected individuals, which were chosen from 140 cholesterol values of 28 subjects that were taken from the article. In addition to the five cholesterol values, and their average, our Table I also includes another item, namely, the cholesterol variation number (CVN). 

Serum Cholesterol Determination by Gas-Liquid Chromatography Clin. Chim. Acta 43(2) 257-265 (1973) CA 78 94490V... 

Huang, T.C., Chen, C.P., Wefier, V., and Raftery, A. 1961. A Stable Reagent for the Lieber-mann-Burchard Reaction. Application to Rapid Serum Cholesterol Determination. Analytical Chemistry, 33, (10), 1405-1407. 

Fig. 6 a. Mean of single serum cholesterol determinations of male office personnel in Metropolitan New York City, stratified according to age. Each specific age category is comprised of a minimum of 18 and... 

Lolekha, P.H., Srisawasdi, P., Jearanaikoon, P., Wetprasit, N., Sriwanthana, B., KroU, M.H., 2004. Performance of four sources of cholesterol oxidase for serum cholesterol determination by the enzymatic endpoint method. Clin. Chim. Acta 339, 135—145. 

Ellerbe, P, Meiselman S, Sniegoski LT, Welch MJ, and White E V (1989) Determination of serum cholesterol by a modification of the isotope dilution mass spectrometric definitive method. Anal Chem 61 1718-1723. 

Wl. Wengeler, H., Greten, H., and Seidel, D., Serum cholesterol esterification in liver disease. Combined determinations of lecithin cholesterol acyltransferase and lipoprotein-X. Eur. J. Clin. Invest. 2, 372-378 (1970). 

The fall in LDL concentration is apparent in 4 to 7 days. The decline in serum cholesterol is usually evident by 1 month. When the resins are discontinued, serum cholesterol usually returns to baseline within 1 month. Cholesterol may rise even with continued use determine serum levels periodically. 

Phenothiazines may increase serum cholesterol, spinal fluid protein, and urinary urobilinogen levels decrease protein bound iodine yield false-positive urine bilirubin tests interfere with urinary ketone and steroid determinations. 

Standard lipid screening to obtain a cholesterol profile for the risk of cardiovascular disease routinely reports total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. Cholesterol values are reported in milligrams per deciliter of blood (mg/dL). Different organizations have made recommendations for normal cholesterol levels, but these must be interpreted carefully, as they are contingent on other risk conditions. For example, the recommendations for smokers or those with a family history of heart disease will be lower for someone without these conditions. The National Center for Cholesterol Education (NCEP) endorsed by the American Heart Association believes that LDL is the primary cholesterol component to determine therapy. LDL cholesterol accounts for 60—70% of blood serum cholesterol. An LDL less than 160 mg/dL is recommended for individuals with no more than one risk factor and less than 100 mg/dL for individuals with coronary heart disease. NCEP classifies HDL, which comprises between 20% and 30% of blood cholesterol, below 40 mg/dL as low. Triglycerides are an indirect measure of VLDL cholesterol. The NCEP considers a normal triglyceride level as less than 150 mg/dL. 

The measurement of serum cholesterol is one of the most common tests performed in the clinical laboratory. Hypercholesterolemia (high blood cholesterol levels) can be the result of a variety of medical conditions. Among the conditions implicated are diabetes mellitus, atherosclerosis, and diseases of the endocrine system, liver, or kidney. High blood cholesterol levels do not point to a specific disease determination of cholesterol is used in conjunction with other clinical measurements mainly for confirmation of a particular diseased condition, rather than for diagnosis of a specific ailment. 

Some studies have shown increased risks of violent death and depression in subjects with reduced serum cholesterol concentrations. Serum and membrane cholesterol concentrations, the microviscosity of erythrocyte membranes, and platelet serotonin uptake have been determined in 17 patients with hypercholesterolemia (21). There was a significant increase in serotonin transporter activity only during the first month of simvastatin therapy. This suggests that within this period some patients could be vulnerable to depression, violence, or suicide. This is an important paper, in that it explains why mood disorders are not regularly seen in clinical trials with statins, as has been summarized in a recent review (3). 

Recently the means by which pectin lowers cholesterol levels and even the validity of this effect have been questioned. Upon finding no bile salt binding capacity for soluble pectin, Baig and Cerda (76) proposed that pectin lowered serum cholesterol levels by forming insoluble complexes with the serum low density lipoproteins (LDL) which transport circulating cholesterol. Complexing of LDL by citrus pectin was observed in vitro, but the way in which pectin or some component thereof enters the blood stream to effect such binding in vivo has not been determined. 

Method-dependent measurements can be grouped by sector. For example, in the clinical fields there are cases where some higher order reference materials are required for IVD methods, such as for determination of glucose in human serum. It is also required of reference laboratories in specific measurement methods. These issues are now under the responsibility of JCTLM (Joint Committee on the Traceability of Laboratory Medicine of CCQM). CENAM has developed a reference material for glucose and cholesterol determination in human serum, and certified by IDMS, which is under review by JCTLM for the use by reference laboratories in any country applying a reference method. 

Apart from the fact that a linear calibration can be performed, bracketing offers excellent precision and accuracy. With the determination of serum cholesterol as an example, Cohen et al. (1980) showed that the replication error on five different serum pools was characterized by a CV of 0.17% with a set-to-set variability of 0.32%. For each serum average, a standard error (considering all causes of variability combined) of 0.16% CV was obtained. The undetected systematic error (bias) in this study was estimated to be smaller than 0.5%, while White et al. (1982), using two different IDMS methods, found serum glucose concentrations to agree within 1%. 

The latter term really represents VLDL cholesterol. It is now recognized that serum apoprotein determinations provide the best cardiovascular disease risk evaluation high levels of ApoB-100, especially ApoLp(a), are associated with a high disease risk, but high levels of ApoA-I are associated with a low risk. The optimal LDL/HDL cholesterol ratio is 3 or less. 

Solvent-free enzymatic interesterification of milk fat alone or with other fats or fatty acids provides the most acceptable route for modification of the triacylglycerol structures in milk fat and further research and development in this field is expected to provide physical and physiological benefits. From a nutritional perspective, it is of interest to examine the effects of randomized milk fat on serum cholesterol. Christophe et al. (1978) reported that substitution of native milk fat with chemically-randomized interester-ified milk fat reduced cholesterol levels in man. However, others found that there was no effect on serum cholesterol levels in man as a result of substitution of ezymatically randomized milk fat (De Greyt and Huyghebaert, 1995). Further studies are required to determine if interesterilied milk fat provides a nutritional benefit. 

Little is known of the in vivo effect of manganese on cholesterol metabolism. Doisy (6) observed a decrease in serum cholesterol (from 206 to 80 mg/dl) in a single manganese deficient human subject. Reports of other human studies conducted to determine the influence of dietary manganese on cholesterol metabolism were not found. 

The purpose of the second study was to determine the effect of changes in kind and amount of dietary fat, with or without manganese supplementation, on blood serum cholesterol and triglyceride levels and on manganese status of human adults. The project was comprised of a 5-day pre-period and four, 14-day experimental periods. 

Some studies have shown increased risks of violent death and depression in subjects with reduced serum cholesterol concentrations. Serum and membrane cholesterol concentrations, the microviscosity of erythrocyte membranes, and platelet serotonin uptake have been determined in 17 patients with hypercholesterolemia... 

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