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Biomedical subjects

K Lippel

Publications and source records attributed to K Lippel.

At least 19 recordsLinked to original sources
PubMed1991

Selenium, retinol, retinol-binding protein, and uric acid. Associations with cancer mortality in a population-based prospective case-control study.

Using a prospective case-control study design, baseline levels of plasma selenium, retinol, and retinol-binding protein, and baseline blood uric acid levels were compared in 136 case patients who subsequently died from cancer and 238 matched control subjects. Subjects were followed for an average of 8 1/2 years. In matched analyses, selenium levels were lower in case patients with gastrointestinal or prostate cancer; retinol levels, lower in those with gastrointestinal or breast cancer; retinol-binding protein levels, lower in case patients with gastrointestinal cancer; and uric acid levels, lower in a group with "other" cancers. However, only the uric acid association with "other" cancers and the retinol-binding protein association with gastrointestinal cancer were statistically significant (P < or = .02) in conditional logistic regression analyses controlling for multiple potential covariates. Relationships for each of the substances varied by cancer site, and although some relationships were suggestive, our results point to the need for larger studies with adequate numbers for site-specific analyses.

Adult↗
PubMed1990

Serum lipids and lipoproteins of Hispanics, 1982-84.

This report presents descriptive data for serum lipids and lipoproteins by age, sex, and selected socioeconomic variables. This information is from the Hispanic Health and Nutrition Examination Survey, a sample survey of selected groups of civilian noninstitutionalized Hispanic persons residing in selected area of the United States, that was conducted during the period 1982-84.

Adult↗
PubMed1986

A comparison of methods for the estimation of plasma low- and very low-density lipoprotein cholesterol. The Lipid Research Clinics Prevalence Study.

Using data from over 10 000 men, women, and children who participated in the Lipid Research Clinics prevalence studies, we have examined the formula adopted by Friedewald et al for estimating plasma or serum concentrations of low-density lipoprotein cholesterol (LDL-C) when (for economy, or in the absence of an ultracentrifuge) only fasting total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) concentrations are measured in milligrams per liter, ie, LDL-C = TC-(HDL-C + 0.20 X TG). Values for LDL-C obtained by use of the Friedewald formula were compared with values derived from the Lipid Research Clinics ultracentrifugal procedure for LDL-C, which was used as a reference. Participants who were pregnant, who had not fasted, or whose plasma contained chylomicrons or floating beta-lipoproteins were excluded. We concluded that a better estimator for LDL-C was provided by the equation LDL-C = TC-(HDL-C + 0.16 X TG), since it produced an error (relative to the reference method) of lesser magnitude than the previous formula. The expression 0.16 X TG (0.37 X TG when measurements are reported in millimoles per liter) also produced a more accurate estimate of very low-density lipoprotein cholesterol relative to values obtained by the standard Lipid Research Clinics procedure for this component. The proposed formula is more precise for plasmas or sera with a TG concentration within the normal range.

Adolescent↗
PubMed1986

Populations and methods for assessing dyslipoproteinemia and its correlates. The Lipid Research Clinics Program Prevalence Study.

This article presents the basic methods and populations of the Lipid Research Clinics (LRC) Program Prevalence Study. The purpose is to provide a frame of reference for the other articles in this monograph; hence, the populations and major data collected are described briefly, as are procedures for enhancement of data quality and approaches to statistical analysis. More detailed descriptions for some procedures are included in the pertinent articles. The two sequential screening examinations of the Prevalence Study provided 60,502 participants from centers in the United States and Canada for the first phase and 13,852 for the second. The monograph is based on data from 11,657 white and 644 black participants aged 6 years or older screened at both visits.

Adolescent↗
PubMed1986

Alterations in clinical chemistry levels associated with the dyslipoproteinemias. The Lipid Research Clinics Program Prevalence Study.

Mean blood levels of eight components of clinical chemistry and the proportion of participants with abnormal chemistry values were calculated for persons with six dyslipoproteinemias (DLPs) and compared with findings from normolipidemic participants in 10 defined North American Lipid Research Clinics Program study populations. Most of the significant differences in mean chemistry levels were in persons with type IIB and IV DLP, and were characterized by higher mean levels of serum alkaline phosphatase, glucose, SGOT, and uric acid, and by lower mean levels of total bilirubin and thyroxine. Similarly, persons with type IIB and IV DLP were more likely to have significantly increased percentages of abnormal clinical chemistry values than were normolipidemics, but for a given chemistry this was rarely over 10% to 15% higher. With the exception of some participants with types IIB and IV DLP, the DLPs detected in these study populations were not associated with a substantial prevalence of abnormal clinical chemistry values and, by inference, were not frequently associated with the diseases or metabolic abnormalities for which these chemical abnormalities are indicators.

Adult↗
PubMed1983

Central laboratory quality control in the National Cooperative Gallstone Study.

This article presents the rationale, selection, operation, and quality control of the Central Serum and Central Bile Laboratories utilized by the National Cooperative Gallstone Study. The external quality control protocols were designed to monitor long-term stability of the analytical procedures and to measure the precision of the measurements as affected by the collection, labelling, storage, shipping, and laboratory methods. For both laboratories, the assessment of long-term stability by pool standards failed to produce the data necessary to come to relevant conclusions. Several of the problems involved, however, did lead to protocol changes that increased the reliability of the laboratory data. The use of duplicate measurements to monitor precision was more successful and demonstrated acceptable performance of these systems. This article describes the external quality control surveillance procedures employed in the NCGS, their strengths and weaknesses, statistical methods for the analysis of such quality control programs, and the implications for the final statistical analyses of the clinical trial patient data.

Bile↗
PubMed1981

Multilaboratory evaluation of an ultrafiltration procedure for high density lipoprotein cholesterol quantification in turbid heparin-manganese supernates.

High density lipoprotein (HDL) can be quantitated by measurement of cholesterol in supernates after precipitation of low and very low density lipoprotein (LDL and VLDL) with heparin and Mn(2+). Supernatant turbidity, often observed with hypertriglyceridemic specimens, indicates incomplete sedimentation of LDL/VLDL and precludes accurate quantitation of HDL. Ten Lipid Research Clinic Laboratories compared an ultrafiltration technique for clearing turbid heparin-Mn(2+) supernates to current methods involving repeat precipitation of either the original specimen after dilution or the d > 1.006 g/ml fraction after removal of VLDL from the initial specimen by ultracentrifugation. Results for ultrafiltration of 429 turbid supernates averaged only slightly higher (1.0-1.1 mg/dl) than results by the dilution or ultracentrifugation methods on the same specimens, but this difference was found to be significant (P < 0.005). The agreement of the ultrafiltration method with the other two methods is indicated by the following linear regression equations: a), ultrafiltration = (0.964 x ultracentrifugation) + 2.4 mg/dl, and correlation coefficient = 0.926; and b), ultrafiltration = (0.936 x dilution) + 3.3 mg/dl, and correlation coefficient = 0.933. We conclude that ultrafiltration of turbid heparin-Mn(2+) supernates is a convenient alternative to precipitation after either dilution or removal of VLDL.-Warnick, G. R., J. J. Albers, P. Bachorik, J. Turner, C. Garcia, C. Breckinridge, K. Kuba, S. McNeely, G. Hillerman, P. King, R. Muesing, B. Most, and K. Lippel. Multi-laboratory evaluation of an ultrafiltration procedure for high density lipoprotein cholesterol quantification in turbid heparin-manganese supernates.

Chemical Phenomena↗
PubMed1980

Effects of sample aging on total cholesterol values determined by the automated ferric chloride-sulfuric acid and Liebermann-Burchard procedures.

To investigate the comparability of three commonly used methods for determination of total cholesterol in plasma in several studies, we used fresh plasma samples as well as plasmas and reference sera that had been stored frozen at -15 degrees C for as long as several years. Duplicate determinations by the manual method of Abell et al. (J. Biol. Chem. 195: 357, 1952) were compared with estimates from one to five continuous-flow analyzers by the ferric chloride-sulfuric acid procedure and also with estimates from five to 13 continuous-flow analyzers by the Liebermann-Burchard procedure with calibrator, as part of the laboratory standardization activities of the Lipid Research Clinics. The agreement among all three procedures was generally within acceptable limits (within 5% of the manual method) when plasmas or sera were fresh or had been frozen for less than one month. Results by the manual method of Abell et al. agreed well with those by the automated Liebermann-Burchard method for samples that had been stored at -15 degrees C for as long as two years. However, the automated ferric chloride-sulfuric acid procedure often showed unacceptably high values (as compared with those from the manual method) for samples that had been stored frozen for a year or more. With the ferric chloride-sulfuric acid method, measured cholesterol concentration increased about 2.5% per year of storage for at least two years. We conclude that reference sera of plasmas that have been kept in long-term frozen storage (-15 degrees C) are not suitable for ongoing standardization of the automated ferric chloride-sulfuric acid assay for cholesterol.

Autoanalysis↗
PubMed1979

Automated determination of total plasma cholesterol: a serum calibration technique.

The automated (AutoAnalyzer II) determination of cholesterol in nine serum pools in the concentration range 3.465-8.871 mmol/l, gave results that were approximately 10% higher than reference values when the analyses were based on unesterified cholesterol standards containing the same amount of water as the sample extracts (1963 analyses in 12 laboratories during a 12 month period; automated value = 0.032 + 1.10 X (Reference value)). A serum calibration procedure was successful ilues, and was equally effective in correcting the values observed for aliquots of 368 fresh-frozen plasma samples analyzed in each of the 12 laboratories during a 38 month period.

Autoanalysis↗
PubMed1979

Four electrophoretic methods compared for diagnosis of type III hyperlipoproteinemia.

Blood drawn from 192 probands and 1129 first-degree relatives who were participants in a collaborative family study of hyperlipoproteinemia at nine Lipid Research Clinics was used to prepare aliquots of whole plasma and top (d less than 1.006 g/mL) and bottom (d greater than 1.006 g/mL) ultracentrifugal fractions. Each aliquot was analyzed at a central laboratory by electrophoresis on paper, agarose, and polyacrylamide gel, and by a combined electrophoretic precipitation technique. The electrophoretograms were evaluated for the presence or absence of a "floating-beta" lipoprotein band. All four methods agreed completely for 92.3% of the samples. An additional 2.0% of the samples were in agreement for three electrophoretic methods, but the paper electrophoretic results were not interpretable. Another 1.9% were considered to be "floating-beta" positive by paper electrophoresis but negative by the other three electrophoretic methods.

Chemical Precipitation↗
PubMed1978

Analytical performance and comparability of the determination of triglycerides by 12 Lipid Research Clinic laboratories.

Twelve Lipid Research Clinic laboratories performed automated fluorometric triglyceride analyses on four control serum pools of known concentration by a modified Hantzsch reaction. The analyses were done during a two-year period, with use of common standards, methodology, and quality-control procedures. Estimates of analytical bias, variability, and short- and long-term trends for each instrument and for the entire group of LRC instruments are presented. High accuracy, precision, and interlaboratory comparability were achieved through rigorous standardization and control of the entire analytical procedure. Individual instrument biases varied from an average of 4.9% below to 1.0% above reference values. Between-run variability was often less than within-run variability and interlaboratory variation was substantially less than intralaboratory variation. The total standard deviation for all instruments ranged from 37 to 63 mg/liter. Only 5 to 14% of this variation was due to differences among instruments. The among-instruments standard deviation ranged from 12 to 17 mg/liter; the between-run, within-instrument standard deviation ranged from 29 to 46 mg/liter, and within-run standard deviation from 27 to 40 mg/liter. The significance of the results for long-term collaborative studies is discussed.

Analysis of Variance↗
PubMed1978

External quality-control survey of cholesterol analyses performed by 12 lipid research clinics.

We report accuracy and precision achieved in the automated analysis for cholesterol in a long-term multilaboratory study, presenting and evaluating the significance of data accumulated by 12 Lipid Research Clinics (LRC's) in the analysis of 18 unknown surveillance pools during three years. The average bias for all pools and for 13 autoAnalyzer II (Technicon Instruments Corp., Tarrytown, N.Y. 10591) instruments in the 12 clinics was -0.41% (range -1.2 to +0.3%), as compared to values established by reference methodology. The regression equation relating observed cholesterol values (y) to reference values (x) was: y = 0.35 + 0.977x. The bias varied from pool to pool (-2.3 to +5.3%), positive biases being observed for pools with cholesterol concentrations less than 1.4 g/liter, and negative biases for those pools with higher concentrations. Total standard deviations ranged between 25 and 75 mg/liter, and total CV's for most individual instruments were between 1 and 3%. Of the variability for a particular pool, less than 20% was due to differences among instruments, and within- and between-run variabilities were approximately equal. These trends were the same as those previously observed [Clin. Chem. 23, 1744 (1977)] in the analysis of bench control pools of known cholesterol concentration.

Autoanalysis↗