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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↗
PubMed1976

Medical economics survey-methods study: design, data collection, and analytical plan.

This paper describes the background, methodology, data collection, and analytical plan of a pilot investigation conducted under contract for the National Center for Health Statistics during 1975. The objective was to determine the cost effectiveness of a variety of strategies under consideration for national application to develop previously unavailable information on utilization of, and the costs and payments for, health care. Detailed data on health care utilization and expenditures were collected periodically from a panel of 691 Maryland households over a six-month interval. Issues to be tested through a random experimental design include whether periodicity (monthly vs bimonthly interviews) and type of contact (in-person vs telephone) are significant factors in the cost effectiveness of this type of survey. An extensive record check involving all providers and third-party payers identified in the household survey was carried out. Record information will be used to 1) provide a basis for measuring accuracy of household data, 2) fill gaps in household knowledge, and 3) determine whether a subset of the record sources can provide adequate information for correcting household data. The household survey resulted in an initial response rate of 77.5 per cent with a subsequent attrition rate over six months of 13.6 per cent. Signed permission to access record data was obtained for 84.9 per cent of the individuals completing the entire survey. The most intensive survey strategy, monthly, mostly in-person contact, resulted in the lowest participation. The analytical plan presents details of the approaches to be taken in making judgments on the relative accuracy and completeness of data obtained by the various survey strategies and the contribution made by availability of data from record sources.

Adolescent↗
PubMed2000

National Inventory of Clinical Laboratory Testing Services (NICLTS). Development and test distribution for 1996.

CONTEXT: A statistically valid inventory of the distribution, both geographic and by laboratory type, of clinical and anatomical laboratory testing in the United States is needed to assess the impact of the Clinical Laboratory Improvements Amendments of 1988 and to provide information for other health care and public health policy decisions. OBJECTIVE: To present initial US laboratory testing volume data compiled by the National Inventory of Clinical Laboratory Testing Services. DESIGN: Stratified random sample of laboratories performing testing in 1996 with data on the number of laboratory tests performed, identified by method and analyte. Data were collected by field tabulators (moderate- or high-complexity laboratories) or through a mail/telephone survey (waived or provider-performed microscopy laboratories) for each site. PARTICIPANTS: Laboratories that were enrolled in the 1996 Online Certification Survey and Reporting System, maintained by the US Health Care Finance Administration, and that performed laboratory testing during 1996. MAIN OUTCOME MEASURE: Laboratory testing distribution for 1996 in the United States by analyte, method, and specimen type. RESULTS: An overall response rate of 79% provided data from 757 moderate- or high-complexity laboratories and 1322 waived or provider-performed microscopy laboratories. The estimated total US testing volume for 1996 was 7.25 +/- 1.09 billion tests. Laboratories performing complex testing, defined as greater than 16 method/analyte/specimen type combinations, comprised 16% of the US laboratories by survey site, but performed 80% (95% confidence limits, 43% to 100%) of the testing volume. Glucose analysis was the most frequently performed test. Automated hematology and chemistry analyzers were the most frequently used methods. CONCLUSIONS: A statistically valid, consistent survey of the distribution of US laboratory testing was obtained. Simple analysis of these data by laboratory type and geographic region can provide insights into where laboratory testing is performed. The study design allows extensions that will facilitate collection of additional data of importance to public health and medical care delivery.

Clinical Laboratory Techniques↗
PubMed2000

Comparability of thermodynamic data--a metrological point of view.

In order to compare and to interpret chemical measurements, compliance with general rules of metrology is compulsory. Such rules are the more important the more the chemical measurements are applied under circumstances where material assets and goods or immaterial values like health may be affected. Metrology of chemical measurements attempts to define rules for achieving comparability and for guaranteeing quality of analytical data. Thermodynamic data are commonly derived from a set of analytical measurements. Comparability among thermodynamic data is an important issue especially for those data to be applied in politically sensitive issues of environmental prognosis, long-term safety assessment of nuclear waste repositories in deep geological formations and assessment of environmental impact of technical intervention in the geosphere. Taking the data evaluation step in the traceability chain of thermodynamic data as an example, the existing thermodynamic data is shown to be affected by deficiencies in comparability and quality that may severely limit its dependability in environmental prognosis. The need for a metrologically acceptable approach is demonstrated. Statistical concepts improving a reliable assignment of meaningful measurement uncertainty to a thermodynamic datum are presented. Unresolved issues, i.e. measurement uncertainty of a pH measurement, hampering the construction of a traceability chain are outlined.

Journal Article↗
PubMed2006

Certified reference materials for inorganic and organic contaminants in environmental matrices.

Chemical measurements often constitute the basis for informed decision-making at different levels in society; sound decision-making is possible only if the quality of the data used is uncompromised. To guarantee the reliability and comparability of analytical data an intricate system of quality-assurance measures has to be put into effect in a laboratory. Reference materials and, in particular, certified reference materials (CRMs) are essential for achieving traceability and comparability of measurement results between laboratories and over time. As in any other domain of analytical chemistry, techniques used to monitor the levels and fate of contaminants in the environment must be calibrated using appropriate calibration materials, and the methods must be properly validated using fit-for-purpose matrix-matched CRMs, to ensure confidence in the data produced. A sufficiently large number of matrix CRMs are available for analysis of most elements, and the group of chemicals known as persistent organic pollutants, in environmental compartments and biota. The wide variety of analyte/level/matrix/matrix property combinations available from several suppliers enables analysts to select CRMs which sufficiently match the properties of the samples they analyse routinely. Materials value-assigned for the so-called emerging pollutants are scarce at the moment, though an objective of current development programmes of CRM suppliers is to overcome this problem.

Environmental Pollutants↗
PubMed2002

Towards rapid and unique curve resolution of low-field NMR relaxation data: trilinear SLICING versus two-dimensional curve fitting.

In this work an alternative method, named SLICING, for two-dimensional and noniterative T(2) decomposition of low-field pulsed NMR data (LF-NMR) is proposed and examined. The method is based on the Direct Exponential Curve Resolution Algorithm (DECRA) proposed by W. Windig and A. Antalek (1997, Chemom. Intell. Lab. Syst.37, 241-254) and takes advantage of the fact that exponential decay functions, when translated in time, retain their characteristic relaxation times while only their relative amounts or concentrations change. By such simple translations (slicing) it is possible to create a new "pseudo" direction in the relaxation data and thus facilitate application of trilinear (multiway) data-analytical methods. For the application on LF-NMR relaxation data, the method has two basic requirements in practice: (1) two or more samples must be analyzed simultaneously and (2) all samples must contain the same qualities (i.e., identical sets of distinct T(2) values). In return, if these requirements are fulfilled, the SLICING (trilinear decomposition) method provides very fast and unique curve-resolution of multiexponential LF-NMR relaxation curves and, as a spin-off, calibrations to reference data referring to individual proton components require only scaling of the resulting unique concentrations. In this work the performance of the SLICING method (including multiple slicing schemes) is compared to a traditional two-dimensional curve fitting algorithm named MATRIXFIT through application to simulated data in a large-scale exhaustive experimental design and the results validated by application to two small real data sets. Finally a new algorithm, Principal Phase Correction (PPC) based on principal component analysis, is proposed for phase rotation of CPMG quadrature data, an important prerequisite to optimal SLICING analysis.

Algorithms↗
PubMed2000

Data evaluation for soft drink quality control using principal component analysis and back-propagation neural networks.

This work describes an alternative for chemical data research, with the aim of evaluating finished product quality. Analytical data for additives in soft drinks are interpreted by the use of multivariate data analysis: principal component analysis (PCA), factor analysis, cluster analysis, and artificial neural networks. Taking into account various chemical components like sorbic, benzoic, and ascorbic acids; saccharose; caffeine; Na, K, Ca, Mg, Fe, Zn, Cu, P, and B, soft drinks were characterized and classified. The ratios of Na, K, Ca + Mg, P, and K/Na have been studied. The application of PCA, cluster analysis, and artificial neural networks showed that combination of these chemometric tools offers effective means for modeling and classifying soft drinks in accordance with their contents in additives and heavy metals.

Beverages↗
PubMed1999

Effects of storage and cooking on the iodine content in iodized salt and study on monitoring iodine content in iodized salt.

In order to ensure that the intake of iodine from iodized salt is adequate, the effects of cooking, storage and iodination on iodine content in iodized salt have been studied. For monitoring the analytical performance, a quality control examination was also undertaken. The loss of iodine was greater when salt was stored in plastic bag than in glass bottle. The loss was greater in fortified salt stored at 37 degrees C and under 76% humidity than in that at 20-25 degrees C and under lower humidity. The retention of iodine varied with the kind of foods and also was influenced by the water content of cooked food. In general, the retention of iodine during cooking varied considerably (from 36.6% to 86.1%). The iodine concentration in salts varied greater from 3.0 to 100.3 mg/kg in salt for markets, and from 0 to 90.0 mg/kg in salts for households. 48.3% of samples from markets were found to be in compliance with national standards (30-50 mg/kg), and 72.0% of samples from households were in compliance with national standard (20-50 mg/kg). Analytical data collected from 8 of the cooperative laboratories for an analytical reference material showed a 95% confidence interval of the population mean for both precision and accuracy, falling within X +/- 2SD and passing quality control examination.

Food Preservation↗
PubMed1982

[Determination of the catalytic activity of lipase by the continuous titration method].

Development of a standardized procedure for the titrimetric assay of lipase has been suggested. Comparative studies with triolein und olive oil were therefore undertaken. Optimal conditions, such as pH, substrate and glycocholate concentrations, etc. were determined for the assay with triolein. The results agree with those obtained earlier with olive oil as substrate. Experience with the quality of various reagents used since 1966 is reported. Problems of methodology are then discussed, especially the incomplete characterization and purity of the bile acid preparations, and their effects on the test conditions. A critical analysis shows that two point tests with modifications of the continuous titration cannot give reliable results. Haemolysis and its effect on catalytic activity of lipase are used to illustrate the consequences of the uncritical acceptance of data from the literature. Furthermore, the required sensitivity of the analytical equipment, operational errors, and the uncritical evaluation and interpretation of analytical data are discussed. The first experiments to be performed with the addition of colipase are described, and the question of whether this cofactor should be used routinely for test purposes is considered. The problem of whether lipoproteinlipase can be quantitatively inhibited is discussed. In view of the outlay on apparatus and the time required for the assay, continuous titration is definitely not suitable for routine screening purposes. On the other hand, simpler methods that give reproducible quantitative results have not yet been developed.

Catalysis↗
PubMed1985

Maximizing the efficiency of a study on alcohol-related birth defects by means of data collection and analytic strategy dissociation.

Application of the terms "prospective" and "retrospective" to quasi/experimental research designs used in clinical investigations is often ambiguous; they often lack specification as to whether they apply to data acquisition, analytic strategy, or both. Data may be collected prospectively by preplanned protocol or retrospectively by chart review. In addition, the direction of analysis may be prospective--comparing differential outcomes for at-risk and not at-risk (exposed/not exposed) groups--or retrospective--comparing differential preceding risks for affected and nonaffected groups. Prospective data collection is advantageous in assuring the availability of crucial variables for an entire sample, but prospective analytic strategies may be inefficient, underestimating effect sizes, particularly when the outcome of interest is rare or the effect, even if large, is seen in only a small proportion of cases. In a prospective multilinear regression model of risks for lowered birthweight for gestational age, 2% of the variance was explained by alcohol variables after adjustment for confounding. In comparison, a similar multilinear regression of case-control sample, in which the frequency of the abnormal outcome is raised, showed 18% of the variance explained by alcohol variables. Data collection and analytic strategies may be dissociated. Although some statistical power may be lost because of reduced sample size, synthetic case-control analysis is efficient in examining small effects. It also has the advantage of decreasing the size of the database to be managed and the time required for analysis. Using this approach, it is feasible to perform virtually any analysis that can be done on a mainframe on medium-sized departmental computer system.

Birth Weight↗
PubMed2003

Tc99m-sestamibi scintigraphy and cell proliferation in primary hyperparathyroidism: a causal or casual relationship?

BACKGROUND: Sestamibi scintigraphy has become the fundamental technique for preoperative location of hyperfunctioning glands responsible for hyperparathyroidism, especially in the case of adenomas. However, little is known about the mechanisms of tracer uptake and retention by these glands, mechanisms that have been related to an increased gland metabolism. Our goal was to determine whether there is a relationship between the positive result of gammagraphy with sestamibi, for diagnosing the location of parathyroid adenomas, and the cell proliferation index. PATIENTS AND METHODS: Six glands corresponding to sestamibi false negatives and 12 true positives were studied in patients with single-adenoma primary hyperparathyroidism. The following data were recorded in all the patients: age, gender, clinical and analytical data, gland weight, and parathyroid hormone (PTH)/gland weight ratio. An immunohistochemical study of the glands was also done with the use of Ki67, with determination of the mean proliferation index of each group for comparison purposes. RESULTS: On comparing the 2 groups, we found no differences between the clinical or analytical parameters. Differences were found only for proliferation index-(5.7% in true positive glands versus 0.3% in false negative glands (P <.004). CONCLUSION: Tracer (sestamibi) uptake by hyperfunctioning parathyroid adenomas in primary hyperparathyroidism might be linked to a higher gland metabolism activity, probably related to cell proliferation.

Adenoma↗