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PubMed1996

Standard reference materials and data quality assurance in the biomedical analysis of trace elements.

Accurate and precise analytical data of the concentrations of bio-analytes in bioclinical studies are of fundamental importance. Quality assurance procedures should always be performed to check the overall analytical work. This can be conveniently performed if appropriate standard reference materials with known concentrations of the analyte object of study are available. This paper underlines the key points related to the production and use of biological standard materials for trace element analysis. In particular, the present situation in the field of trace element determination in human biological fluids and the related problems are illustrated. The considerations given in this work may contribute to the preparation of the new biomarker standard materials.

Biomarkers↗
PubMed1997

[Differences in nutrient intake using different nutrient databases-- an example].

Mean dietary intake calculated from 25 7-day-food records by means of the three nutrient data bases modified Souci/Fachmann/Kraut (mSFK) 1986/87, extract of Bundeslebensmittelschlüssel (BLS) version 2.1, and extract of BLS version 2.2 revealed comparable results only for four of 27 nutrients considered. The greatest deviations were found for zink, fluoride, iodine, vitamin D, vitamin C, and dietary fiber. Comparing the revised BLS version 2.2 and mSFK, the differences in fluoride, iodine and dietary fiber intake data were markedly lower than found with the comparison of BLS 2.1 and mSFK; statistically significant differences no longer existed for the vitamins C and A (equivalents). As expected, using the mSFK data base with some missing fields for analytical data underestimation of nutrient intake could be shown for the trace elements zink, fluoride and iodine. With regard to the given results of the investigated group, care has to be taken with some nutrient intake data gathered by means of BLS 2.1, too.

Diet Records↗
PubMed2004

Retrieval of missing data for meta-analysis: a practical example.

OBJECTIVES: To examine the feasibility of retrieving missing outcome data for summary meta-analyses using an example dealing with the effects of aerobic exercise on lipids and lipoproteins in adults. METHODS: Missing lipid and/or lipoprotein data from a currently developed meta-analytic data base were requested by means of electronic mail from 39 of 174 (22.4 percent) eligible studies. Binary logistic regression was used to examine whether year of publication and country were significant predictors for whether data would be provided. RESULTS: Of the thirty-nine studies from which data were requested, usable data were received for thirteen (33.3 percent) of the studies. The addition of these previously missing data decreased the percentage of eligible studies that would have had to be excluded by 33.5 percent (from 22.4 percent to 14.9 percent). Neither year of publication nor country in which the study was conducted (United States versus other) were significant predictors of whether missing data would be provided or not (p > .05). CONCLUSIONS: Moderate success was achieved in the acquisition of missing outcome data dealing with the effects of aerobic exercise on lipids and lipoproteins in adults. However, whether this level of response is true in other areas of research needs to be determined by additional research.

Clinical Trials as Topic↗
PubMed1999

The German Food Code and Nutrient Data Base (BLS II.2).

This article describes the conception and structure of the German Food Code and Nutrient Data Base (BLS). The data bank contains approx. 12,000 coded foods, menus and menu components in different stages of processing with up to 158 nutritional data for each product. Since comparatively few analytical data on the composition of foods are available, the majority of the data in the BLS are based on nutritional data calculated from recipes. Thus, a standard instrument for an uninterrupted (no missing values) evaluation of consumption surveys is made available.

Databases as Topic↗
PubMed1990

Individual-differences assessment of the relationship between change in and initial level of adult cognitive functioning.

Methodological factors may have been partially responsible for the inconsistency in findings from previous investigations into the relationship between change in, and initial level of, adult cognitive functioning. An alternative data-analytic procedure is proposed and applied to data from 277 men (25-76 years of age at initial testing) over 3 measurement occasions (interwave intervals of 6.7 years). Performances on both the Benton Revised Visual Retention Test (BVRT) and the Wechsler Adult Intelligence Scale (WAIS) Vocabulary subtest were analyzed. The findings demonstrate that the significant negative relationships between change and initial status, found on both tests, were partially a function of measurement error. Once adjustments were made for errors of measurement, the previously significant negative relationship for the BVRT data became significantly positive, whereas for the WAIS the relationship remained significantly negative, although to a lesser degree. The importance of accounting for errors of measurement is discussed.

Adult↗
PubMed1998

The use of stable isotope labeling and liquid chromatography-tandem mass spectrometry techniques to simultaneously determine the oral and ophthalmic bioavailability of timolol in dogs.

Assays have been established for the quantitation of timolol and its 13C3- and 2H9-stable-isotope-labeled analogs in plasma and urine using liquid chromatography with atmospheric-pressure chemical-ionization tandem mass spectrometry. For the analysis of urine, underivatized timolol and its labeled analogs are monitored while timolol in plasma is assayed down to concentrations of 0.2 ng/mL after derivatization with phosgene. The great power of this technique is illustrated by simultaneously assaying three different species of timolol in plasma and urine obtained from dogs receiving simultaneous ophthalmic, oral, and intravenous doses of unlabeled and [2H9]- and [13C3]-labeled timolol. Thus, the ophthalmic and oral bioavailabilities of timolol are measured in a single experiment rather than as a three-phase crossover experiment. This approach yields accurate and precise analytical data, obviates intrasubject variability, and saves both analytical and animal resources.

Administration, Oral↗
PubMed1985

Synthesis of peptide labelled with p-iodophenylalanine which corresponds to the first amphipathic region of apolipoprotein C-I.

The amino terminal fragment (1-15) of apolipoprotein C-1, H-Thr-Pro-Asp-Val-Ser-Ser-Ala-Leu-Asp-Lys-Leu-Lys-Glu-Phe14-Gly was prepared by the solid phase method. However, the phenylalanine residue at position 14 was replaced with p-iodophenylalanine in the chemical synthesis. The preparation of t-butyloxy-carbonyl-p-iodophenylalanine is described. After completion of the synthesis, the product was deprotected and cleaved from the resin with liquid HF. The peptide was purified by gel filtration on Sephadex G-25 and preparative high performance liquid chromatography. The purified material was shown to be homogeneous by amino acid analytical data and by chromatography in three different analytical reversed phase HPLC systems. The peptide was then labelled by the chloroamine-T procedure and good incorporation of 125I was obtained. After purification of the product by gel filtration on Biogel P-2, the labelled pentadecapeptide was tested for ability to bind to Very Low Density Lipoproteins (VLDL) in the following manner: VLDL was isolated from normolipemic serum by ultracentrifugal flotation and 100-microliter samples were incubated with labelled material dissolved in 200 microliter of 0.5 M NaCl, 0.02 M sodium phosphate buffer, pH 7.4 at 37 degrees for 30 min. The VLDL fraction was again isolated by ultracentrifugal flotation and the incorporation of radioactivity into the lipoprotein was measured. Under these conditions, a sample of [3H]-native apolipoprotein C-I was incorporated to an extent of 83% of the total sample, while the [125I]-pentadecapeptide exhibited an incorporation of 8.7%.

Amino Acid Sequence↗
PubMed1989

Receiver operating characteristic (ROC) methodology: the state of the art.

Receiver operating characteristic (ROC) methodology has been increasingly used in medical applications in the last 10 years. The text by Swets and Pickett has popularized the technique and the journal Medical Decision Making (1981--) provides a forum for further methodologic issues. In this article, I will (1) describe the nature of the data generated by ROC studies; (2) evaluate the choices of summary indices of performance (accuracy); (3) outline the data-analytic techniques used, and how to incorporate data from multiple observers and multiple "readings"; (4) review proposed alternatives to the commonly used binormal ROC model; and (5) discuss issues, such as verification bias, and challenges, such as multicenter comparative imaging studies and the difficulty of obtaining "truth data", which need to be addressed when adapting ROC methods to medical contexts.

ROC Curve↗
PubMed1994

[Malignant tumors of the Vater's ampulla. Presentation of 28 cases and review of the literature].

We present a study of 28 patients, treated for adenocarcinoma of Vater's ampulla. We emphasize the distinct behavior of each one of the peri-ampullar tumors, those which affect Vater's ampulla yielding the best prognosis. We gathered data regarding gender, age, clinical manifestations, and analytical data. The confirmatory diagnosis gives us 100% of CPRE cases. All of the patients were submitted to surgical treatment with anatomic pathological confirmation of the diagnosis, be it pre or postoperative. We practiced curative surgery in 57.2% of the cases and palliative in 42.8% of the cases. We observed postoperative complications in 17.8% of the patients and peroperative mortality in 3.5%. Actual survival of the series of patients for whom exeretic surgery was performed is significantly superior to that of the other patients.

Actuarial Analysis↗
PubMedDate not supplied

Organization and education in occupational safety and health in Maghreb countries.

The Maghreb consists of five countries of North Africa (Mauritania, Morocco, Algeria, Tunisia and Libya) which are members of a socio-economical community called the Union of Arab Maghreb. This paper discusses the organisation of occupational health, medical protection of workers and training in occupational safety and health in these countries. After a review of socio-economic and demographic data and legislative aspects, we report epidemiological and analytic data specific to each country concerning organisation and training in occupational health. Occupational medicine in Algeria, Morocco and Tunisia has progressed but some deficiencies are still observed at several levels. Like countries of the European Union, cooperation between the Maghreb countries in occupational health and safety seems indispensable.

Africa, Northern↗
PubMed2001

Advances in high-throughput mass spectrometry.

The evolution of high-throughput drug discovery is readily apparent as the pharmaceutical industry continues to stress the rapid progression of new chemical entities and biological agents through drug discovery and development pipelines. Mass spectrometry and high performance liquid chromatography-mass spectrometry have played an instrumental role in the support and advancement of all facets of high-throughput drug discovery. The introduction of new instrumentation has extended the breadth of mass spectrometric-based capabilities from the characterization of high-throughput organic synthesis products to early adsorption, distribution, metabolism and excretion profiling. Additionally, advances in the capacity and throughput of mass spectrometry systems have concurrently led to the introduction of data management tools to address automated data reduction, archival and mining, as well as analytical data integration to chemical and biological databases.

Chromatography, High Pressure Liquid↗
PubMed1999

Laparoscopy and laparoscopic ultrasonography for staging pancreatic cancer: critical appraisal.

A pilot study was designed to elucidate the role of staging laparoscopy for determining resectability in patients with pancreatic cancer. The additional value of laparoscopic contact ultrasonography (LCU) was also evaluated with specific regard to its ability to detect hepatic metastases and assess vascular infiltration of the portomesenteric trunk. A consecutive sample of 50 patients referred for operation of a suspected pancreatic cancer were submitted to preoperative contrast-enhanced high-resolution computed tomography (CT) and staging laparoscopy combined with LCU at a university hospital. For those progressing to exploratory laparotomy, the intraoperative findings relating to tumor diffusion and vascular infiltration were compared to CT, laparoscopic, and LCU data. Analytical description of the laparoscopic findings is given. Row data of predicted versus observed vascular infiltration were tabulated for CT and LCU. The sensitivity, specificity, and overall accuracy of each diagnostic test were calculated for comparative analysis. Laparoscopy alone prevented unnecessary laparotomy in 20% of cases. A complete procedure could not be achieved in 28% of patients. Three false-negative staging results occurred. LCU identified small (benign) hepatic nodules not seen by CT in 8% of patients. Sensitivity, specificity, and overall accuracy for assessing vascular infiltration were 82%, 53%, and 69% for CT and 94%, 80%, and 87% for LCU. Laparoscopy was confirmed to be safe and effective for staging pancreatic cancer. Because of its unique capabilities to detect even small peritoneal tumor deposits a quick exploration immediately before laparotomy is advised in all patients. The additional benefit of a more extensive procedure is not supported by our results. Although LCU appears to define the vascular involvement more accurately than conventional CT, the limitation of getting clinically useful ultrasound data in all the patients suggests its adoption in only a selected population.

Adult↗
PubMed2002

Multivariate cubic spline smoothing in multiple prediction.

Given longitudinal data for several variables, including a given outcome variable, it is desired to predict the outcome for a specific individual, or more generally experimental unit, in such a way that the predicted value is both accurate and resistant (i.e. has good cross-validation). There are certain data-analytic difficulties associated with long-term multivariate longitudinal data that must be overcome in the prediction process. This paper provides a program written in the Statistical Analysis System (SAS) programming language, based generally on the Roche-Wainer-Thissen stature prediction model, that enables the researcher to overcome these difficulties.

Computer Simulation↗
PubMed2004

The influence of rural location on utilization of formal home care: the role of Medicaid.

PURPOSE: This research examines the impact of rural-urban residence on formal home-care utilization among older people and determines whether and how Medicaid coverage influences the association between rural-urban location and risk of formal home-care use. DESIGN AND METHODS: We combined data from the 1998 consolidated file of the Medical Expenditure Panel Survey Household Component with data from the Area Resource File to generate the analytical data set. We established two measures of formal home-care utilization: home care reimbursed through any source, and Medicare-reimbursed home health care. Our measures of rural-urban residence included metropolitan counties, nonmetropolitan counties having towns of at least 10,000 people, and nonmetropolitan counties with no towns of 10,000 people. We used logistic regression analyses to examine main effects and interaction effects of Medicaid coverage and residence on the two types of formal home care under controls for person-level characteristics and state fixed effects. RESULTS: The unadjusted logistic analyses demonstrate that older people who reside in the most rural counties (nonmetropolitan counties having no town of 10,000) are significantly more likely than metropolitan residents to use any formal home care and Medicare home health care. The fully adjusted logistic analysis results point to an interplay between residential status and Medicaid coverage with regard to formal home-care use. In comparison with metropolitan residents covered by Medicaid, the adjusted relative risk of any formal home-care use is significantly higher for Medicaid enrollees residing in nonmetropolitan counties having no town of 10,000 people. Use of Medicare home health care is significantly greater for residents of the most rural counties, irrespective of their Medicaid coverage, as well as Medicaid-covered residents of nonmetropolitan counties having a town of at least 10,000 people. IMPLICATIONS: In nonmetropolitan areas, Medicaid may be an important mechanism for linking older individuals with formal home care, especially Medicare home health care, and with the services that generate formal home care. Formal home care, including Medicare home health care, may substitute for less available forms of care in the most rural of nonmetropolitan areas. Therefore, policies that limit access to formal home care could lead to increased service-related vulnerabilities among older rural residents.

Aged↗
PubMed2003

HIV sexual risk-reduction interventions for youth: a review and methodological critique of randomized controlled trials.

The authors review and provide a methodological critique of randomized controlled studies of HIV risk reduction interventions that measured sexual risk behavior outcomes with adolescents. Studies conducted in school, community, and health care settings were reviewed. Overall, 13 of 23 interventions (57%) were effective in reducing sexual risk behavior. Methodological strengths of extant studies included an emphasis on a theoretical framework, evaluation of both individualized and group-intervention formats, use of multiple assessments of risk behavior (including biological outcomes), and inclusion of efficacy and effectiveness trials. Methodological limitations included limited evaluation of theoretical mediators of risk reduction, failure to report effect sizes, and lack of sustained findings. Inconsistencies were found in data analytic procedures and reporting, including how nested designs, skewed data, and attrition were addressed. Recommendations for designing methodologically rigorous interventions are provided.

Adolescent↗
PubMed1999

Software for population pharmacokinetics and pharmacodynamics.

Pharmacokinetic-pharmacodynamic modelling is being used increasingly as a tool in drug development because often in phase III clinical trials only sparse data are available for analysis and so a nonlinear mixed effects modelling approach has to be adopted. Specialist data analytical techniques and software are required to analyse such data. This article reviews some of the software currently available for performing nonlinear mixed effects modelling. A questionnaire was devised and sent to a number of software producers and the findings are presented and discussed in this paper. The programs could be grouped into 3 main categories: parametric and nonparametric maximum likelihood and Bayesian. It was apparent from the questionnaire that software development for population data analysis is a very active area of investigation. The implementation of methodologies varied widely between the packages: some were self-contained programs, whereas others were written within another application, usually a statistical package. They also varied with respect to their ease of use and level of support offered by the software producers. Although robustness and reliability are important concerns, they were not addressed in the present review. Most of the programs surveyed are in continual development.

Animals↗
PubMed2002

The use of tropical bromeliads (Tillandsia spp.) for monitoring atmospheric pollution in the town of Florence, Italy.

The results of an experiment with two species of epiphytic angiosperms (Tillandsia caput-medusae and T. bulbosa) for monitoring polycyclic aromatic hydrocarbons (PAHs) in the air of Florence, Italy, are presented. PAHs are compounds known to be dangerous because of their carcinogenic potential, and among cormophytes, tillands (monocotyledons equipped with peculiar, specialised, epidermal trichomes) are considered promising for air pollution biomonitoring. PAHs data were obtained using GC/MS analysis of plant extracts. Analytical data indicated an increasing trend in time of PAHs bioaccumulation. This result was compared with instrumentally recorded parameters such as meteorological (rain) and environmental ones (PM10), indicating that trichome-operated physical capture of aerial particles was prominent in PAHs bioaccumulation on tillands. SEM (scanning electron microscope) observations confirmed the role of the trichomes. This work indicates that tillands are particularly useful, low-cost biomonitoring organisms inside their area of distribution (all Latin American countries and southern USA) where these plants are easily available, but also wherever the climate allows them to survive.

Air Pollutants↗
PubMed1977

[Central accounting as a model of laboratory diagnosis].

From the experiences in the field of scientific organisation of the last years results a laboratory-diagnostic model with an automatic laboratory, a district laboratory and larger central units, so-called coordination laboratories which work together with about 10 to 20 laboratories and guarantee an up-to-date diagnostic spectre for the whole territory. Apart from the increasing investigation frequency, a constant dilatation of the diagnostic spectre and improved quality control of structural conditions must be taken into consideration. The constructed model which demands the collaboration of all institutions meets these critical problems. A central balancing should also extend to the personal and technical apparative capacity. Apart from this the system is to be extended by further automation in the sense of a machine activity with improvement by control and regulation processes. An electronic data processing improves the functional capacity only when the analytic data processing has achieved a high level. The cooperation in the field of laboratory diagnostics is not only a task in scientific organisation, but in the same way also scientific problems are solved together. The requirements increasing in qualitative and quantitative respect may optimally be fulfilled only by the two partners, clinic and laboratory. With increasing independence the laboratories should in scientific and organizational respect remain a place of meeting for laboratory scientist and physician.

Clinical Laboratory Techniques↗