The determination of total cholesterol in serum by gas-liquid chromatography compared with two other methods.

A gas-liquid chromatographic method is described for the measurement of total cholesterol in serum. The method has been found to be simple, specific and precise. The results have been compared with the results of the enzymatic method of Röschlau, P., Bernt, E. and Gruber, W. (1974) (Z. Klin. Chem. Klin. Biochem. 12, 403) and with the results of an Auto-Analyzer method based on the manual method of Huang, T.C., Chen, C.P., Wefler, V. and Raftery, A. (1961) (Anal. Chem. 33, 1405) and Ness, A.T., Pastewka, J.V. and Peacock, A.C. (1964) (Clin. Chim. Acta 10, 229). The results of the gas-liquid chromatographic and of the enzymatic method show a high degree of correlation. The results of the Auto-Analyzer method are about 0.75 mmol/1 higher than those of the other two methods. The conclusion is drawn that the gas-liquid chromatographic method should be given consideration as a reference method for the measurement of total cholesterol in serum. It is a viable alternative for the generally accepted colorimetric reference method of Abell, L.L., Levy, B.B., Brodie, B.B. and Kendall, F.E. (1952) (J. Biol. Chem. 195, 357).

Mass fragmentographic analysis of total cholesterol in serum using a heptadeuterated internal standard.

A mass fragmentographic method for the determination of total cholesterol in serum using heptadeuterated [25,26,26,26,27,27,27-2H]cholesterol as internal standard is presented. The results obtained are compared with a colorimetric and gas chromatographic method which were previously proposed as reference methods. Criteria for the development of absolute measurement by means of mass fragmentography and stable isotopically labelled internal standards are given. The conclusion is drawn that, at present, mass fragmentographic methods for the determination of total cholesterol in serum do not fulfil the criteria required for absolute methods.

Comparison of the precision of seven analytical methods for the H2O concentration in human serum and urine.

In order to calculate a true renal H2O clearance (U X V/P), serum and urine H2O concentrations have to be known. In this investigation we compared the precision (repeatability) and the ease of performance of 7 H2O assays in human serum and urine. The 3 gravimetric assays (oven-drying, freeze-drying or freeze-drying as well as oven-drying) had a very high precision (coefficients of variation (CV) 0.2-0.4%) and were easy to perform. The precision of mass spectrometry, gas chromatography and titrimetry (Karl Fischer) was better in urine than in serum (ranges of CV 1.2-1.5% in urine vs. 2.4-4.3% in serum), but the precision of osmometry was better in serum than in urine (CV 1.0 vs. 1.6%). Accuracy was not determined as storage effects at 4 degrees C and at -20 degrees C caused insuperable logistic problems. Only small sample volumes are used in titrimetry and gas chromatography, making them more suitable for determinations in babies and animal studies. With titrimetry determinations can be done in a short time. The gravimetric assays appear to reflect the true H2O content of serum and urine, thus enabling calculation of the true renal H2O clearance, which can be of clinical importance in liver, renal and cardiac disease.

Potential of descriptive linear discriminant analysis for studying clinical chemical and haematological data from persons with heterozygous sickle cell disease.

To study the potential of multivariate classification methods in order to obtain more insight into abnormal laboratory data from patients with sickle cell disease, we investigated standard haematological and clinical chemical variables of 18 controls and 37 apparently healthy persons with heterozygous sickle cell disease (Hb AS), all women, using both univariate and multivariate classification methods. In the univariate method, those with Hb AS showed decreased serum log aspartate aminotransferase (log AST) activity, mean corpuscular volume and mean corpuscular haemoglobin (MCH) and increased sodium concentration. The multivariate method identified sodium, potassium, urea, uric acid, log AST, alanine aminotransferase and MCH as the variables that produced maximal separation between persons with Hb As and controls. It increased the 'non-error rate' for classification of persons with Hb AS by 16.4% compared with classification based on the variable, MCH, that produced maximal separation by the univariate method. The frequency distribution of percentage Hb S in the Hb AS group proved bimodal with maximal separation at 37.0% Hb S. The subgroup with 37.0% or less (n = 16) was considered to have concomitant heterozygous alpha-thalassaemia-2. In the univariate method the subgroup characterized by greater than 37.0% Hb S (n = 21) had increased serum sodium and uric acid concentrations, perhaps related to sickle cell nephropathy, whereas the subgroup with less than or equal to 37% Hb S did not. The multivariate method added information to the univariate method by additionally identifying abnormalities in serum potassium and urea concentrations in the former subgroup.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum high density lipoprotein cholesterol levels in women using a contraceptive injection of depot-medroxyprogesterone acetate.

The mean serum high density lipoprotein cholesterol (HDL-C) concentration proved to be significantly lower in 23 women taking depot-medroxyprogesterone acetate (DMPA) as a twelve-weekly injectable contraceptive for at least 1 year, as compared to 23 IUD users. In the DMPA group, no significant difference was found in the mean serum HDL-C concentration, when measured 2, 6 and 12 weeks after a DMPA injection.

PIP: Epidemiologically, an inverse relation between serum HDL-C level (high density lipoprotein cholesterol) and risk for coronary heart disease has been reported. HDL has also been known to serve as a vehicle for transporting cholesterol from the arterial wall to the liver for excretion. However, there are no clinical data for the concept that a drug-decreased serum HDL-C is unfavorable with respect to atherosclerosis and myocardial infarction. This study compares the serum HDL-C level in 23 women who received depot medroxyprogesterone acetate (DMPA) as a 12-weekly injectable progestational contraceptive with that of a comparable control group of 23 IUD users. Both groups were selected on the basis of age, bodyweight, and alcohol consumption. HDL-C and serum triglyceride levels were measured by an enzymatic method. The serum HDL-C level was significantly lower in the DMPA group than in the IUD group (t=4.30, p= 0.001). The difference was attributed to the progestational effect of the DMPA. The lapse of time after a DMPA injection did not affect the serum HDL-C level, an unexpected finding as the average serum MPA level rises steeply during the 1st week after DMPA injection and then declines gradually to a relatively low value after 12 weeks. DMPA should not be prescribed to women with abnormally high risk for atherosclerosis (eg, heavy smokers, and women with adiposity and/or diabetes mellitus).

[Injectable contraceptive, DMPA, serum HDL cholesterol and heart infarct]. / Prikpil, serum-HDL-cholesterol en hartinfarct.

PIP: In 23 women who had used the injectable contraceptive depot medroxyprogesterone acetate (DMPA) for at least 1 year, the mean serum high-density lipoprotein cholesterol (HDL-C) level was distinctly lower than in 23 women carrying an IUD. The high serum DMPA levels during the 1st few weeks after a subsequent DMPA injection, and the low levels 12 weeks after the injection were found to be associated with the same (low) serum HDL-C level. For this reason, a fall in the serum HDL-C level in DMPA users is probably not a direct effect of the DMPA, but rather an indirect effect of the diminished production of endogenous estrogens in the ovaries of DMPA users. Though the investigation does not justify definite conclusions, it appears advisable not to prescribe DMPA to women with an increased risk of atherosclerosis and myocardial infarction. (author's)^ieng

Evaluation of the enzymatic ammonia method for urine on the Du Pont automatic clinical analyzer.

The enzymatic method for ammonia with the Du Pont Automatic Clinical Analyzer was tested in our laboratory. The method is very suitable for urine samples although the method was released by Du Pont only for plasma samples. The results correlated well with those obtained by a method based on the Berthelot indophenol reaction and by a method based on the use of an ammonium electrode, which has an ammonium ion selective membrane. The day-to-day coefficient of variation is about 2 and 4% at concentration levels of 100 and 50 mumol/1 respectively. The measured and relative ammonia concentration are linearly related. Recovery of added known amounts of ammonium is complete and no interference from glucose, urea, creatinine and uric acid could be demonstrated. Recommendations are given for handling blood and urine samples before analysis.

The significance of indirect costs-application to clinical laboratory test economics using computer facilities.

The significance of indirect costs in the cost price calculation of clinical chemistry laboratory tests by way of the production centres method has been investigated. A cost structure model based on the 'production centres' method, the Academisch Ziekenhuis Groningen (AZG) 1-2-3 model, is used for the calculation of cost and cost prices as an add-in tool to the spreadsheet program Lotus 1-2-3. The system specifications of the AZG 1-2-3 cost structure model have been extended with facilities to impute all relevant indirect costs to cost centres by aid of allocation rules, which can be chosen freely. The inference is made that as indirect costs play a more important part in decision-making processes concerning planning and control, the specification of the relation to the cost centres should be determined in a more detailed way. The AZG 1-2-3 cost structure model has therefore been extended in order to increase the significance as a management tool for laboratory management.

Prostatic acid phosphatase: comparison of radioimmunoassay and enzyme activity assay.

Aspects of the clinical use of an enzymatic assay and a double antibody radioimmunoassay for prostatic acid phosphatase are compared. Standard blood sample collection and transport did not have a negative effect on the results of either assay. Our results show no substantial advantage in the use of a radioimmunoassay but emphasize the reliability of the enzymatic assay using alpha-naphthylphosphate as a substrate with respect to its predictive value and specificity in diagnosis and followup of patients with prostatic carcinoma.

Patterns in clinical chemistry requests.

For each patient sample that is presented to the clinical chemistry laboratory a combination of various tests can be requested. This combination or profile will depend on the condition of the patient, and hence also on the requesting hospital department. Several techniques were applied to detect and describe patterns in tests requested by the cardiology, hepatology and nephrology sections of the out-patient's Department for Internal Medicine. Comparison of the frequencies of ordering the tests showed significant differences between these sections. Cluster analysis and multidimensional scaling were used to show similarities and differences in the test profiles that were used by the sections. These techniques are useful for generating hypotheses, but the statistical significance of the clustering found is difficult to assess.

Exploring multivariate clinical chemical routine data concerning three major disease groups.

In preparation for multivariate analysis, an exploratory study has been undertaken to investigate the relative position, separability, homogeneity and shape of three major disease groups, using data from a clinical chemical routine package.The data set consists of 46 hepatology patients, 50 nephrology patients and 46 cardiology patients, and the measured blood levels include 20 common clinical chemical routine assays. Missing value problems were avoided by deleting some of the variables and objects.A univariate analysis was used as the basis ofa rescaling of the data.Bivariate (pairwise) plots of some major assays each show limited separation. The set of three such plots of the three major principal components reveals more distinction between the groups than was offered by univariate analysis. Three-dimensional extensions of these techniques allow better insight than any of the two-dimensional plots, but these three-dimensional versions require more plots for complete interpretation.Non-linear mapping of the data is the best way of retaining the distances and a fairly good separation is achieved in the plot. The plot is less informative about shape and relative position of the classes.Representation of the data as pictures of faces does not offer additional information and visual clustering is worse than in any of the techniques mentioned.During the analysis many assumed properties of the data are confirmed and a good starting pointfor multivariate classification is attained. Easy visual detection of outliers is offered by all techniques. Unfortunately, valuable information is lost in this data set by deleting some incomplete variables.

Zinc in plasma and serum: influence of contamination due to the collection tubes.

The contamination caused by rubber stoppers of collection tubes preceding the determination of zinc in plasma and serum was investigated. The use of evacuated blood collection tubes (EBC-tubes), normally used for the collection of serum samples, could give rise to an average artificial increase of normal serum zinc concentrations of about 250%. Heparin containing EBC-tubes, used for the collection of plasma, and plain EBC-tubes of an experimental production appeared to be suitable for correct zinc determinations. There was no difference between the serum and plasma zinc levels of fifty volunteers.

Effect of experimental cholestasis on neuromuscular blocking drugs in cats.

Pancuronium, Org 6368 and gallamine were compared in control cats and in cats with experimental cholestasis. A decrease in the plasma clearance and a prolongation of neuromuscular blockade with Org 6368 and pancuronium were found in the latter; no significant difference was detected in the biotransformation pattern of Org 6368 and pancuronium compared with controls. Inhibition of hepatic uptake of Org 6368 and pancuronium in extrahepatic cholestasis might explain the significant alterations in the pharmacokinetics of the two steroid neuromuscular blocking drugs. The pharmacokinetics of gallamine were normal during cholestasis. The results suggest that, under pathological conditions involving increased plasma concentrations of bile salts, neuromuscular blocking agents that are cleared from the plasma by the liver may have an impaired hepatic uptake and consequently a prolonged duration of action.

Enterohepatic circulation in the rat.

Several compounds, in particular bile acids, undergo enterohepatic circulation (EHC). Limited data are available on the pathophysiologic aspects of this circulation. In the present study we describe a surgical technique in rats that allows a long-term, reversible interruption of the EHC and monitoring of peripheral blood levels without direct surgical intervention. This technique excludes the effects of anesthesia and surgical trauma. The model's validity has been tested extensively. We used this animal model to investigate acute and chronic effects of interruption and subsequent restoration of the EHC on (a) nutritional status, (b) plasma cholesterol levels and hepatic cholesterol synthesis, and (c) biliary bile acid, phospholipid, and cholesterol excretion. Interruption of the EHC resulted in an increased food intake and enhanced fecal energy loss, caused by a less efficient intestinal absorption. Plasma cholesterol concentrations declined immediately after the interruption of the EHC, but returned to almost control values during bile diversion. A marked overshoot followed the subsequent restoration of the EHC. Hepatic cholesterol synthesis showed a five-fold increase after 8 days of bile diversion but returned to control values within 2 days after restoration of the EHC. After interruption of the EHC, bile acid, phospholipid, and cholesterol excretion decreased sharply but stabilized after 3 h at 7.6%, 20%, and 23%, respectively, of their initial values. Bile acid output, representing hepatic synthesis, slowly increased over 4 days, but never exceeded 13% of its value during intact EHC. Subsequent restoration of the EHC could rapidly reverse the observed effects of the interruption. The animal model described in the present study is an excellent tool in studying the acute and chronic effects of disturbances of the EHC.

Injurious effect of EDTA contamination on colorimetry of serum iron.

Colorimetry of iron in serum with Ferrozine (as used in the Technicon SMAC) or with bathophenanthroline (as used in the Du Pont aca) is influenced by EDTA, in contrast to such measurements with atomic absorption spectroscopy. Therefore EDTA contamination should be avoided with these colorimetric methods. If, however, contamination with EDTA is suspected, addition of zinc sulfate to serum or to the SMAC "ascorbic acid reagent" will cancel the influence of EDTA on measurements of iron in the SMAC.