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PubMed2000

[Developoment of qualifications in German nursing care--results of current data analysis].

Nursing provides a service catering to the needs of the individual and, as such, makes its own contribution towards community health care. Apart from organizational and instrumental determinants, manpower resources are of central significance in this context. The number of staff employed in nursing, their qualifications and competences are all factors which fundamentally influence the quality and efficiency of nursing care. Based on current data, the following article will first describe which manpower resources are available in the individual nursing sectors. It will then articulate as a central theme some of the main problems in professional training at the various levels (general, advanced and further education), including Germany's comparatively new university and college degrees in nursing. The results of our analysis indicate, on the one hand, that there is movement towards an improved professional profile in nursing, which could be classified as optimizing manpower resources. For example, far more than two thirds of all nursing staff and other care workers have completed three-year professional training courses. In addition, nursing trainees overproportionately graduate from junior levels of secondary schools. It may, furthermore, be noted that nursing continues to be in high demand as a vocational profession and that there has been a professional upgrade in particular at the teaching and leadership levels. On the other hand, however, we can make out anti-professional developments which contribute to an impairment of manpower resources in nursing. A comparison of 1996 and 1999 figures shows that the number of qualified staff in the care of the elderly has decreased whereas the number of untrained staff has increased by six times. In spite of heavier work loads there has been no increase in the number of staff and trainees in hospital nursing over the past few years. And, with the introduction of statutory insurance covering ongoing nursing care, various semi-professional trainee programs have emerged, leading to a partial displacement of qualified staff. In conclusion, the authors will reflect on how to overcome such developments and further optimize manpower resources in nursing.

Aged↗
PubMed2005

Feature selection and classification for microarray data analysis: evolutionary methods for identifying predictive genes.

BACKGROUND: In the clinical context, samples assayed by microarray are often classified by cell line or tumour type and it is of interest to discover a set of genes that can be used as class predictors. The leukemia dataset of Golub et al. 1 and the NCI60 dataset of Ross et al. 2 present multiclass classification problems where three tumour types and nine cell lines respectively must be identified. We apply an evolutionary algorithm to identify the near-optimal set of predictive genes that classify the data. We also examine the initial gene selection step whereby the most informative genes are selected from the genes assayed. RESULTS: In the absence of feature selection, classification accuracy on the training data is typically good, but not replicated on the testing data. Gene selection using the RankGene software 3 is shown to significantly improve performance on the testing data. Further, we show that the choice of feature selection criteria can have a significant effect on accuracy. The evolutionary algorithm is shown to perform stably across the space of possible parameter settings - indicating the robustness of the approach. We assess performance using a low variance estimation technique, and present an analysis of the genes most often selected as predictors. CONCLUSION: The computational methods we have developed perform robustly and accurately, and yield results in accord with clinical knowledge: A Z-score analysis of the genes most frequently selected identifies genes known to discriminate AML and Pre-T ALL leukemia. This study also confirms that significantly different sets of genes are found to be most discriminatory as the sample classes are refined.

Algorithms↗
PubMed2026

Scale reliant mixed effects models enhance microbiome data analysis.

Linear models, including those used for differential abundance analyses, are frequently used in microbiome research to assess how experimental conditions (e.g., disease state or age) affect microbial abundance. Linear mixed-effects models (MEMs) extend linear models to accommodate complex designs, such as longitudinal sampling or hierarchical study structures. However, when applied to microbiome data, existing MEM approaches suffer from high false positive and false negative rates because sequence counts are compositional - they reflect relative rather than absolute abundances. Current methods attempt to overcome this limitation through normalization, but these approaches rely on strong, often unrealistic assumptions about the unmeasured biological scale (e.g., total microbial load). Here we introduce scale-reliant mixed-effects models (SR-MEM), which extend our earlier scale-reliant inference framework by explicitly modeling uncertainty in the unmeasured scale via user-defined probability distributions. By treating scale as a latent variable rather than fixing it through normalization, SR-MEM enables robust inference for complex experimental designs. SR-MEM can incorporate external scale measurements (e.g., flow cytometry, qPCR) or leverage scale information from independent studies to further improve inference. Across simulations and multiple real-world case studies, SR-MEM consistently controls the false discovery rate while maintaining comparable or higher power than standard approaches relying on normalization or bias correction. In reanalyses of published datasets, SR-MEM yields results that are more reproducible across studies and more consistent with known biological and pharmacological effects. SR-MEM provides a principled and practical framework for mixed-effects modeling of microbiome sequence count data in the presence of unmeasured biological scale. By avoiding normalization-based assumptions and instead propagating scale uncertainty through inference, SR-MEM improves error control and reproducibility in longitudinal and hierarchical studies. An accessible implementation is provided in the ALDEx3 R package.

Microbiota↗
PubMedDate not supplied

Long-term resource use and cost of percutaneous transluminal coronary angioplasty versus stenting in the elderly: a retrospective claims data analysis.

OBJECTIVE: Although the benefits of coronary stenting have been demonstrated in several large clinical trials, controversy remains as to whether stenting results in long-term cost savings compared to percutaneous transluminal coronary angioplasty (PTCA). The objective of this study was to evaluate the resource use and cost (Medicare payment) of PTCA versus bare stent in actual practice over a 2-year period. METHODS: The data for this study came from the 1996 through 1998 Standard Analytic Files that contain 5% of Medicare claims. The rates of repeat revascularization procedures and hospitalizations were reported at 1 and 2 years. Costs associated with inpatient admission, outpatient procedures, physician services, skilled nursing facility admissions, and home health-care services were included to perform a comprehensive assessment. Regression analysis was performed to test for cost differences controlling for case-mix variation between the patient groups. RESULTS: The selection process yielded 3782 PTCA patients and 2690 stent patients for analysis. The rate of revascularization was 26.7% for the PTCA group and 22.2% for the stent group at 2 years. The mean total cost for the initial procedure was 13,724 dollars for PTCA and 15,021 dollars for stenting. At 2 years, the total cumulative cost was 32,654 dollars for the PTCA group and 32,102 dollars for the stent group, a difference that was not statistically significant. CONCLUSION: Although the difference in the rate of repeat revascularization procedures between PTCA and stenting is not as large as those reported in clinical trials, bare stents are cost-neutral when compared to PTCA for the Medicare population.

Aftercare↗
PubMed2005

Can the published cost analysis data for delivery of an efficient primary angioplasty service be applied to the modern National Health Service?

Despite the clinical benefits and safety profile of primary percutaneous coronary intervention (PCI), the health care system in the UK has been slow to adopt this strategy as first line management for ST segment elevation myocardial infarction. The cost implications of a 24 hour a day, seven days per week primary PCI service and the absence of an existing efficient working model within the National Health Service (NHS) framework are two of the major deterrents for provision of such a service. The existent cost effectiveness data for primary PCI is critically reviewed, with particular reference to the NHS.

Angioplasty, Balloon, Coronary↗
PubMedDate not supplied

Effects of sample attrition and data analysis in the Retirement History Study.

Bias can be created through the attrition of respondents in panel studies of older people. After a review of previous studies, a change in the method of examining attrition is suggested. Tests comparing those eligible to respond and those actually continuing in the panel are reported for five waves of data from the Retirement History Study. Results indicate that this data set is relatively free of bias caused by respondent attrition. Although caution is urged, attrition is suggested to be less of a factor in this data set and in panel studies in general than earlier studies involving samples of older individuals might indicate.

Aged↗
PubMed2001

A new data analysis method to determine binding constants of small molecules to proteins using equilibrium analytical ultracentrifugation with absorption optics.

In principle, equilibrium analytical ultracentrifugation (AU) can be used to quantify the binding stoichiometry and affinity between small-molecule ligands and proteins in aqueous solution. We show here that heteromeric binding constants can be determined using a data-fitting procedure which utilizes a postfitting computation of the total amount of each component in the centrifuge cell. The method avoids overconstraining the fitting of the radial concentration profiles, but still permits unique binding constants to be determined using measurements at a single wavelength. The computational program is demonstrated by applying it to data obtained with mixtures of a 500-Da molecule and interleukin-2, a 16-kDa protein. The 1:1 binding stoichiometry and heteromeric dissociation constants (K(ab)) determined from centrifuge data at two different wavelengths are within the 4-9 microM range independently determined from a functional assay. Values for K(ab) have been obtained for ligands with affinities as weak as 500 microM. This AU method is applicable to compounds with significant UV absorbance (approximately 0.2) at concentrations within approximately 5- to 10-fold of their K(ab). The method, which has been incorporated into a user procedure for IgorPro (Wavemetrics, Oswego, OR), is included as supplementary material.

Inhibitory Concentration 50↗
PubMed1993

Preliminary X-ray data analysis of crystalline cowpea chlorotic mottle virus.

Crystals of cowpea chlorotic mottle virus (CCMV) that diffract X-rays to 3.1 A resolution were grown in a succinate-PEG solution buffered at pH 3.3. The crystals are in space group P2(1)2(1)2(1) with unit cell dimensions of a = 381.26 A, b = 381.26 A, and c = 408.59 A. Four particles occupy the unit cell, placing a single virion in the crystallographic asymmetric unit. Diffraction intensities measured from 196 films collected at the Cornell High Energy Synchrotron Source accounted for 55% of the theoretically possible data to 3.2 A. Unit cell dimensions and rotation function analyses of the X-ray data revealed that the particles were organized in a pseudo-tetragonal relationship with the pseudo-fourfold axis along the crystal c axis. Analysis of electron micrographs of two-dimensional crystals of CCMV revealed a remarkable similarity between these and planes of particles perpendicular to the crystallographic c axis in the three-dimensional crystal.

Crystallization↗
PubMed2004

Predictive factors of survival in patients with advanced colorectal cancer: an individual data analysis of 602 patients included in irinotecan phase III trials.

BACKGROUND: The infusional LV5FU2 and Arbeitsgemeinschaft Internische Onkologie (AIO) regimens are used widely in the treatment of advanced colorectal cancer. Irinotecan combined with these regimens increases survival in front-line treatment. Irinotecan also improves survival in second-line treatment. PATIENTS AND METHODS: Univariate and multivariate analyses based on the individual data of 602 patients included in two phase III trials were performed to determine predictive factors of survival in advanced colorectal cancer. RESULTS: Three factors were independently associated with a better progression-free survival: weight loss <5% [hazard ratio (HR) 1.25; 95% confidence interval (CI) 1.00-1.58], World Health Organization performance status (WHO PS) 0-1 (HR 1.29; 95% CI 1.08-1.54) and irinotecan (CPT-11)-containing regimens (HR 1.48; 95% CI 1.03-2.13). Five factors were independently associated with a better overall survival: weight loss <5% (HR 1.67; 95% CI 1.29-2.14), WHO PS 0-1 (HR 1.88; 95% CI 1.27-2.75), one or two metastatic sites (HR 1.24; 95% CI 1.01-1.53), alkaline phosphatase values not over twice the normal range (HR 1.71; 95% CI 1.30-2.24) and CPT-11-containing regimens (HR 1.31; 95% CI 1.07-1.61). CONCLUSIONS: The present analysis confirms that CPT-11-based chemotherapy regimens are independently associated with a better survival in patients with advanced colorectal cancer. Age was not identified as a prognostic factor in this analysis.

Adult↗
PubMed2001

Matched case-control data analysis with selection bias.

Case-control studies offer a rapid and efficient way to evaluate hypotheses. On the other hand, proper selection of the controls is challenging, and the potential for selection bias is a major weakness. Valid inferences about parameters of interest cannot be drawn if selection bias exists. Furthermore, the selection bias is difficult to evaluate. Even in situations where selection bias can be estimated, few methods are available. In the matched case-control Northern Manhattan Stroke Study (NOMASS), stroke-free controls are sampled in two stages. First, a telephone survey ascertains demographic and exposure status from a large random sample. Then, in an in-person interview, detailed information is collected for the selected controls to be used in a matched case-control study. The telephone survey data provides information about the selection probability and the potential selection bias. In this article, we propose bias-corrected estimators in a case-control study using a joint estimating equation approach. The proposed bias-corrected estimate and its standard error can be easily obtained by standard statistical software.

Bias↗
PubMed2004

Statistical pixelwise inference models for planar data analysis: an application to gamma-camera uniformity monitoring.

In this paper two tests based on statistical models are presented and used to assess, quantify and provide positional information of the existence of bias and/or variations between planar images acquired at different times but under similar conditions. In the first test a linear regression model is fitted to the data in a pixelwise fashion, using three mathematical operators. In the second test a comparison using z-scoring is used based on the assumption that Poisson statistics are valid. For both tests the underlying assumptions are as simple and few as possible. The results are presented as parametric maps of either the three operators or the z-score. The z-score maps can then be thresholded to show the parts of the images which demonstrate change. Three different thresholding methods (naive, adaptive and multiple) are presented: together they cover almost all the needs for separating the signal from the background in the z-score maps. Where the expected size of the signal is known or can be estimated, a spatial correction technique (referred to as the reef correction) can be applied. These tests were applied to flood images used for the quality control of gamma camera uniformity. Simulated data were used to check the validity of the methods. Real data were acquired from four different cameras from two different institutions using a variety of acquisition parameters. The regression model found the bias in all five simulated cases and it also found patterns of unstable regions in real data where visual inspection of the flood images did not show any problems. In comparison the z-map revealed the differences in the simulated images from as low as 1.8 standard deviations from the mean, corresponding to a differential uniformity of 2.2% over the central field of view. In all cases studied, the reef correction increased significantly the sensitivity of the method and in most cases the specificity as well. The two proposed tests can be used either separately or in combination and are capable of showing trends and/or the magnitude of difference between images acquired under similar conditions with high positional and statistical precision. In addition to gamma camera quality control, they could be applied to any pair (or set) of registered planar images to detect subtle changes, e.g. a set of scintigrams or conventional radiographs of a patient before, during and after treatment.

Computer Simulation↗
PubMed1991

Use of high coverage reference libraries of Drosophila melanogaster for relational data analysis. A step towards mapping and sequencing of the genome.

Three differently made, primary Drosophila cosmid libraries of 16-fold genome coverage have been generated. Also, a jumping library has been created by a new method that takes advantage of methylation differences between genomic DNA and vector. Thirdly, two cDNA libraries have been picked. All these libraries have been arrayed on high-density in situ filters, each containing 9216 clones. As a reference system, such filters are distributed and identified clones are provided. Single-copy probes have identified on average 1.4 cosmids per genome equivalent. Together with cytogenetically mapped yeast artificial chromosomes, the libraries are also being used for physically mapping the genome, mainly by oligonucleotide fingerprinting and pool hybridizations. cDNA clones are further examined by a partial sequencing analysis by oligomer hybridization.

Animals↗
PubMed2006

Fast gradient elution reversed-phase liquid chromatography with diode-array detection as a high-throughput screening method for drugs of abuse. II. Data analysis.

In Part I of this work, we developed a method for the detection of drugs of abuse in biological samples based on fast gradient elution liquid-chromatography coupled with diode array spectroscopic detection (LC-DAD). In this part of the work, we apply the chemometric method of target factor analysis (TFA) to the chromatograms. This algorithm identifies the target compounds present in chromatograms based on a spectral library, resolves nearly co-eluting components, and differentiates between drugs with similar spectra. The ability to resolve highly overlapped peaks using the spectral data afforded by the DAD is what distinguishes the present method from conventional library searching methods. Our library has a mean list length (MLL) of 1.255 and a discriminating power of 0.997 when both retention index and spectral factors are considered. The algorithm compares a library of 47 different compounds of toxicological relevance to unknown samples and identifies which compounds are present based on spectral and retention index matching. The application of a corrected retention index for identification rather than raw retention times compensates for long-term and column-to-column retention time shifts and allows for the use of a single library of spectral and retention data. Training data sets were used to establish the search and identification parameters of the method. A validation data set of 70 chromatograms was used to calculate the sensitivity (correct identification of positives) and specificity (correct identification of negatives) of the method, which were found to be 92% and 94%, respectively.

Algorithms↗
PubMed1993

An air quality data analysis system for interrelating effects, standards, and needed source reductions: Part 12. Effects on man, animals, and plants as a function of air pollutant impact.

The impact-effect mathematical model, developed in 1991, improves on a previous mathematical model, and was developed to predict biological response as a function of air pollutant impact. Impact is defined here as exposure duration multiplied by air pollutant concentration raised to an exponent (t.cd). This paper's purpose is to plot and regress example biological effects as a function of air pollutant impact to determine how well the plotted data fit the impact-effect model for three target populations: man, animals, and plants (a wide range of life forms). The three biological effects are: for man, lung function decrease after exposure to ozone (O3); for animals, mouse mortality after exposure to nitrogen dioxide (NO2); and for plants, leaf injury after exposure to O3. The three resultant regression equations account for a substantial amount of the data variance: 95 percent for lung function, 92 percent for leaf injury, and 73 percent for mouse mortality. The model fits the animal and plant data that cover both acute and chronic exposures. The animal exposures ranged from 6 min to 1 yr. The plant exposures ranged from 0.75 to 552 h.

Adult↗
PubMed2004

A dynamic system model-based technique for functional MRI data analysis.

Signals in functional magnetic resonance imaging (fMRI) are influenced by physiological fluctuations in addition to local brain activity. We have proposed a dynamic system model-based technique for separation of signal changes related to brain activation inputs from those related to physiological fluctuations. We applied this technique to a visual fMRI experiment to determine the validity and feasibility of this technique for fMRI data analyses. Gradient-echo echo planar images were obtained from 12 healthy volunteers with a Siemens ALLEGRA operating at 3 T, with a repetition time of 500 ms, echo time of 20 ms, field of view of 200-210 mm, matrix size of 64 x 64, and slice thickness of 5 mm. Twelve runs with two stimulation periods of varied duration (2-8 s) with 8-Hz flickering illumination were obtained for each subject. Local signal changes were modeled by an autoregressive model with two exogenous inputs, a visual stimulation input and a global reference signal. Local signal changes were appropriately predicted not only for stimulation periods but also resting periods. A significant linear relationship was found between model static gain based on the dynamic system modeling and beta coefficient based on a general linear model (GLM) analysis for active voxels in the primary visual cortex (analysis of covariance [ANCOVA], P < 0.001; estimated parameter, 0.967; 95% confidence interval, 0.734-1.201). This dynamic system model-based technique is sufficiently accurate and feasible for use in extracting signal changes related to brain activation inputs from measured signals with physiological fluctuations.

Adult↗
PubMed2000

Fatigue data analysis of canine femurs under four-point bending.

When bone is subjected to fatigue loading, micro-cracks initiate and grow. This reduces the mechanical properties and quantitative relationships between stiffness loss and loading cycles may be derived. We developed the relationships between stiffness loss and loading cycles for whole canine femurs subjected to cyclic fatigue in four-point bending. The fatigue data from experiments followed Weibull statistics. When the stiffness loss is less than 15%, a linear relationship is best-fitted (R2 = 0.96, p < 0.0001) between the stiffness loss and loading cycles. However, when the stiffness loss is greater than 30%, a power law relationship is best-fitted (R2 = 0.97, p < 0.0001) between the stiffness loss and loading cycles. Thus, we conclude that the derived relationships between stiffness loss and loading cycles might be useful for the prediction of bone failure under cyclic bending subjected to an initial strain of 2700 microstrain.

Algorithms↗
PubMed2000

[Roaming through methodology. XXII. Application of techniques for longitudinal data analysis].

Longitudinal studies are characterised by repeated measurements of the outcome variable on the same individuals. This implicates that observations are correlated and that statistical techniques, such as linear regression analysis cannot be used. Special longitudinal techniques correct for the dependency in repeated observations by analysing the development of a certain individual in time. Depending on the research question, the distribution of the outcome variable, and the number of repeated measurements, a certain technique should be chosen. Sophisticated longitudinal techniques like generalized estimating equations and random-coefficient models are most recommendable.

Data Interpretation, Statistical↗