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PubMed1998

Statistical approaches to determine analytical variability and specifications: application of experimental design and variance component analysis.

Assessment of analytical variability is recognized as an important factor for the establishment of specifications. Estimation of the variance for an analytical procedure can be accomplished using a variety of approaches. The approach of variance component analysis was applied retrospectively, as well as prospectively, to estimate analytical variance. The prospective approach also included the use of experimental design. Recent new drug substance examples illustrating these approaches are presented. In these examples, the analytical property of potency was evaluated. Factors examined in the experimental design include laboratory, day, analyst, instrument and column. Process variability can also be determined by variance component analysis. For a stable drug substance, combining the analytical and process variances provides an estimate on the total variance for the analytical property of potency. With the total variability statistically derived, an appropriate specification that is consistent with process and analytical capability can be established.

Analysis of Variance↗
PubMed2004

Liquid chromatography of active principles in Sophora flavescens root.

Herbal medicines were one of the major resources for healthcare in earlier stages, and some traditional herbal medicines have been in use for more than 2000 years. Currently, they are attracting more and more attention of the modern pharmaceutical industry, as scientists has become aware that herbs have almost infinite resources for medicine development. This review provides an overview of the analytical approaches applied in the researches concentrated on various aspects of the matrine-type alkaloids in Sophora flavescens root. Emphasis will be laid on the analytical processes of high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), as well as gas chromatography (GC) methods. The sample extraction, separation and detection have been summarized. In addition, the applications of chromatographic determinations are introduced for the main matrine-type alkaloids in S. flavescens root, such as matrine, sophoridine, sophocarpine, lehmannine, sophoramine, oxymartine, oxysophocarpine, cytosine and aloperine. The advantages and limitations of HPLC, CE and GC methods in the analytical applications of the alkaloids are also discussed.

Chromatography, Gas↗
PubMed2005

Increasing the degrees of freedom in existing group randomized trials: the df* approach.

This study describes a method for incorporating external estimates of intraclass correlation to improve the precision for the analysis of an existing group-randomized trial. The authors use a random-effects meta-analytic approach to pool the information across studies, which takes into account any interstudy heterogeneity that may exist. This approach can be used in several different situations to estimate the degrees of freedom available for an adjusted test of the intervention effect in a study where the challenges of group-randomized trials were not fully considered when the study was planned. The authors discuss the limitations of this approach and the circumstances in which it is likely to be helpful.

Humans↗
PubMed1990

Characterization of the efficiency of a cell separation process by the extent of elimination of a contaminating cell type.

A stepwise approach to the selection of an appropriate technique for a cell separation problem is presented in which the preparative purification of cells is linked to their analytical separation. We have introduced the extent of elimination of a contaminating cell type from the cell type which one chooses to purify, as a separation parameter that characterizes the efficiency of a separation process independently of the relative cell composition of the starting material. In order to compare different separation techniques, a preparative fraction boundary needs to be chosen between the cell types. We defined this boundary in terms of the physical property on which the separation is based such that yield and purity of the isolated cell suspension are optimized simultaneously. With this analytical approach, it was found that a similar elutriation technique separated human and equine mononuclear cells equally well and that the separability of human monocytes and lymphocytes improved when the cells were separated by increasing the limiting sedimentation coefficient value of the elutriation chamber in small increments.

Animals↗
PubMed1998

Developmental homologues: lineages and analysis.

Developmental processes present several problems for identifying homologies and analyzing their evolution. Most evolutionary techniques approach homologies from either a taxonomic or a molecular perspective. Approaches that can accommodate many problems of developmental evolution are not well developed. Developmental process and evolutionary lineage complexity lead to a number of largely unappreciated conceptual and analytic problems. Developmental processes can evolve by duplication or diversification. Each process is in a hierarchy of super- and subprocesses. As they evolve, process components may be exchanged with or acquired by those of other processes. Because they do not fit into standard analytic procedures, these situations (including reticulate or reticulate-appearing lineages, partial homologues, iterative features, and the tracing of nontaxonomic and nonmolecular evolutionary lineages) are often ignored or considered illegitimate. Biology's disdain for the dichotomously branching phylogenetic lineages that are the basis of standard analytic approaches is ignored at the risk of making falsely negative homology evaluations. I will present an approach that can accommodate analyses of these situations. The use of nontaxonomic and nonmolecular lineages provides a way to structure comparisons between other entities, as taxonomic lineages structure comparisons among potential homologues. From an informational point of view, any entity (either a structure or process) with an evolutionary history is a potential homologue with a potential evolutionary lineage. Comparing lineages of interacting entities can reveal topological incongruences among them. Methods that identify reticulated taxonomic and molecular lineages should also apply to other lineages. Partial homologues, resulting from reticulated lineages, can be handled in several possible ways. Analytically, such an entity can be treated as a partial homologue, a novel feature, an independent sub-unit, or a unitary feature homologous to the major contributor of its inherited features.

Animals↗
PubMed2005

Methods for confidence interval estimation of a ratio parameter with application to location quotients.

BACKGROUND: The location quotient (LQ) ratio, a measure designed to quantify and benchmark the degree of relative concentration of an activity in the analysis of area localization, has received considerable attention in the geographic and economics literature. This index can also naturally be applied in the context of population health to quantify and compare health outcomes across spatial domains. However, one commonly observed limitation of LQ is its widespread use as only a point estimate without an accompanying confidence interval. METHODS: In this paper we present statistical methods that can be used to construct confidence intervals for location quotients. The delta and Fieller's methods are generic approaches for a ratio parameter and the generalized linear modelling framework is a useful re-parameterization particularly helpful for generating profile-likelihood based confidence intervals for the location quotient. A simulation experiment is carried out to assess the performance of each of the analytic approaches and a health utilization data set is used for illustration. RESULTS: Both the simulation results as well as the findings from the empirical data show that the different analytical methods produce very similar confidence limits for location quotients. When incidence of outcome is not rare and sample sizes are large, the confidence limits are almost indistinguishable. The confidence limits from the generalized linear model approach might be preferable in small sample situations. CONCLUSION: LQ is a useful measure which allows quantification and comparison of health and other outcomes across defined geographical regions. It is a very simple index to compute and has a straightforward interpretation. Reporting this estimate with appropriate confidence limits using methods presented in this paper will make the measure particularly attractive for policy and decision makers.

Computer Simulation↗
PubMed2002

Statistical methods in epidemiology: Karl Pearson, Ronald Ross, Major Greenwood and Austin Bradford Hill, 1900-1945.

The tradition of epidemiological study through observation and the use of vital statistics dates back to the 18th century in Britain. At the close of the 19th century, however, a new and more sophisticated statistical approach emerged, from a base in the discipline of mathematics, which was eventually to transform the practice of epidemiology. This paper traces the evolution of that new analytical approach within English epidemiology through the work of four key contributors to its inception and establishment within the wider discipline.

Epidemiology↗
PubMed1991

Correlations and apparent contradictions in assessment of oxidant stress status in vivo.

Oxidative modifications of biological molecules are essential, but uncontrolled or excessive oxidative activities appear to contribute to many disease states. The mechanisms through which excess oxidant activities cause injury have been studied most extensively for acute responses, particularly for drug-induced tissue damage and cell death, but substantial evidence suggests that chronically elevated oxidative activity may contribute to the development of diseases such as cancer. It is important that the correlation between oxidant stress status and cancer risk be examined directly in humans. A number of methods have been developed for assessing oxidant activities by measuring oxidized products in biological systems, but cross-comparison studies of these different methods are needed. In studies of mechanisms of acute hepatotoxicity, assessments of oxidant stress responses by different analytical methods often have provided data that appear at first glance to be contradictory. Marked oxidant stress responses may be indicated by one or more methods of analysis despite the lack of detectable change in other parameters, whereas in a second experimental model the responses may be reversed. These observations emphasize the need to integrate different analytical approaches into the assessment of oxidant activity in vivo and illustrate the importance for developing a better understanding of the chemical and physiological mechanisms through which the analytical methodologies are related.

Cell Survival↗
PubMed1995

Cost-effectiveness analysis of the Ottawa Ankle Rules.

STUDY OBJECTIVE: To conduct an incremental cost-effectiveness analysis of implementation of the Ottawa Ankle Rules in emergency departments in the United States and Canada. DESIGN: A decision analytic approach to technology assessment. Clinical decision rules that allow physicians to be more selective in their use of radiography were compared with current practice in a decision analytic model. SETTING: A university hospital adult ED. PARTICIPANTS: ED physicians instructed in the use of the Ottawa Ankle Rules for adult patients with ankle injury. RESULTS: Radiography, waiting time, lost productivity, and medicolegal costs were calculated. In the United States, the savings varied between US$614,226 and US$3,145,910 per 100,000 patients, depending on the charge rate for radiography. In Ontario, Canada, the total savings were CAN$730,145 per 100,000 patients. One- and two-way sensitivity analyses that varied the rate of missed fractures, cost of radiography, probability of lawsuits, and cost of lawsuits did not change the results substantially. CONCLUSION: Implementation of the Ottawa Ankle Rules would result in significant savings of health care dollars despite the cost of missed fractures including litigation costs.

Adult↗
PubMed2002

Power calculations for a general class of family-based association tests: dichotomous traits.

Using large-sample theory, we present a unified approach to power calculations for family-based association tests. Currently available methods for power calculations are restricted to special designs or require approximations or simulations. Our analytical approach to power calculations is broadly applicable in many settings. We discuss power calculations for two scenarios that have high practical relevance and in which power previously could only be assessed by simulation studies or by approximations: (1) studies using both affected and unaffected offspring and (2) studies with missing parental information. When the population prevalence is high, it can be worthwhile to genotype unaffected offspring. For many scenarios, high power can be achieved with reasonable sample sizes, even when no parental information is available.

Chi-Square Distribution↗
PubMed1981

Stereological methods in cell biology: where are we--where are we going?

The current state of the art in morphometric cell biology is reviewed by looking at the developmental state of stereological methods, and at the approaches used to arrive at quantitative structure-function correlation. Stereological methods have reached a fairly advanced level of sophistication since mathematical stereology has been developed as a branch of geometric probability theory. The application of these methods in cell biology lags behind, both quantitatively and qualitatively. Among the strategies used in exploiting stereological methods in cell biology the physiological approach (where a change is induced experimentally and its effect on the cells is followed by biochemical and morphometric methods) ranks highest and is still valid. More analytical approaches, such as combining stereology and biochemistry in cell fraction studies, are fraught with difficulties. In considering future developments of stereological methods, the emphasis will have to be 1) on developing procedures for eliminating biases such as section thickness or resolution effects, and 2) on increasing the efficiency of the methods by better sampling rules and improved instrumentation. The future trends in morphometric cell biology might best be served by exploiting the potentials of histochemistry and stereology by combining them with a view to 1) establishing procedures for cell-specific sampling and 2) developing methods towards "molecular morphometry" on the basis of immunocytochemical labeling.

Animals↗
PubMed1990

Cognitive-behavioral approaches to treating borderline and self-mutilating patients.

The cases of three self-injurious patients suffering with borderline personality disorder are briefly presented. From this clinical base, the consultant describes a cognitive-behavioral psychotherapeutic model and how it might be applied to the treatment of these and similar patients. A dialectical behavioral approach is used to describe three major dichotomies and their application. The consultant also illustrates how cognitive-behavioral therapy may be integrated with more dynamic-analytic approaches, and proposes a strategy and methodology that establish and reinforce the treatment alliance in developing a treatment plan.

Adult↗
PubMed2006

Evaluation of multidimensional capillary electrophoretic methodologies for determination of amino bisphosphonate pharmaceuticals.

Alendronate and pamidronate are amino bisphosphonate analogues of pyrophosphate used for the treatment of a variety of bone diseases. Analysis of these compounds is problematic due to their polar ionic nature, lack of a suitable chromophore and chelation properties and current analytical approaches involve extensive sample preparation and derivatization procedures. The potential of multidimensional capillary electrophoretic methodological approaches, which eliminate sample preparation have been evaluated for the analysis of these compounds both in aqueous and urinary matrices. Capillary isotachophoresis (cITP) was employed as a pre-separation and on-line sample concentration step prior to analytical determination using either cITP or capillary zone electrophoresis (CZE) with conductivity detection. Single cITP, cITP-cITP and cITP-CZE approaches were partially validated with respect to repeatability, recovery and linearity of response for both compounds. The increases in sensitivity achievable through increasing injection volume from 30 to 300 microL may render such strategies appropriate for determination of these agents at biologically relevant concentrations with minimal sample work-up.

Alendronate↗
PubMed2006

Immunoaffinity chromatography of abscisic acid combined with electrospray liquid chromatography-mass spectrometry.

Polyclonal antibodies with high specificity for C1-immobilised (+)-cis,trans-abscisic acid (ABA) were raised, characterised by enzyme-linked immunosorbent assay (ELISA) and used for preparation of an immunoaffinity chromatography (IAC) gel. The detection limit of the ELISA was approximately 4.6x10(-10)mol/L. Sensitive electrospray liquid chromatography-mass spectrometry (LC-ESI-MS) methods were also developed with detection limits below 0.1x10(-12)mol. The IAC allowed quick, single-step processing of samples prior to the analyses. The LC-ESI-MS and LC-ELISA techniques were used for comparative estimation of endogenous ABA levels in immunoaffinity purified extracts of normal and water-stressed Nicotiana tabacum L. leaves. The analytical approaches were validated using deuterium- and tritium-labelled internal standards, respectively. The IAC method was found to be highly effective, sensitive and convenient for isolating the target analyte from plant material.

Abscisic Acid↗
PubMed2006

Reactivity-based analysis of domain structures in native replication protein A.

Replication protein A (RPA) is an essential heterotrimeric ssDNA binding protein that participates in DNA repair, replication, and recombination. Though X-ray and NMR experiments have been used to determine three-dimensional structure models of the protein's domain fragments, a complete RPA structural model has not been reported. To test whether the fragment structures faithfully represent the same portions in the native solution-state protein, we have examined the structure of RPA under biologically relevant conditions. We have probed the location of multiple amino acids within the native RPA three-dimensional structure using reactivity of these amino acids toward proteolytic and chemical modification reagents. In turn, we evaluated different structural models by comparing the observed native RPA reactivities with anticipated reactivities based on candidate structural models. Our results show that our reactivity analysis approach is capable of critically assessing structure models and can be a basis for selecting the most relevant from among alternate models of a protein structure. Using this analytical approach, we verified the relevance of RPA fragment models to the native protein structure. Our results further indicate several important features of native RPA's structure in solution, such as flexibility at specific locations in RPA, particularly in the C-terminal region of RPA70. Our findings are consistent with reported DNA-free structural models and support the role of conformational change in the ssDNA binding mechanism of RPA.

Amino Acid Sequence↗
PubMed2002

[Analytical epidemiology--case-control and cohort studies].

BACKGROUND: "The study of the occurrence of disease" is a short but quite precise definition of epidemiology, as it includes both descriptive and analytic approaches. Whereas descriptive studies of the distribution of diseases and their potential causal factors may generate hypotheses about disease aetiology, causal inferences may most safely be drawn from analytical testing through properly designed observational studies. METHODS: The most commonly used observational designs are the retrospective case-control and the prospective cohort studies. In some respects the two designs complement each other. Drawing on some classic epidemiological studies, their main properties in terms of what questions they may answer, what their applicabilities are, as well as their main strengths and weaknesses, are discussed.

Case-Control Studies↗
PubMedDate not supplied

Food allergen detection methods: a coordinated approach.

The levels (1-2%) and increasing severity of allergic responses to food in the adult population are well documented, as is the phenomenon of even higher (3-8%) and apparently increasing incidence in children, albeit that susceptibility decreases with age. Problematic foods include peanut, milk, eggs, tree nuts, and sesame, but the list is growing as awareness continues to rise. The amounts of such foods that can cause allergic reactions is difficult to gauge; however, the general consensus is that ingestion of low parts per million is sufficient to cause severe reactions in badly affected individuals. Symptoms can rapidly-within minutes-progress from minor discomfort to severe, even life-threatening anaphylactic shock in those worst affected. Given the combination of high incidence of atopy, potential severity of response, and apparently widespread instances of "hidden" allergens in the food supply, it is not surprising that this issue is increasingly subject to legislative and regulatory scrutiny. In order to assist in the control of allergen levels in foods to acceptable levels, analysts require a combination of test methods, each designed to produce accurate, timely, and cost-effective analytical information. Such information contributes significantly to Hazard Analysis Critical Control Point programs to determine food manufacturers' risk and improves the accuracy of monitoring and surveillance by food industry, commercial, and enforcement laboratories. Analysis thereby facilitates improvements in compliance with labeling laws with concomitant reductions in risks to atopic consumers. This article describes a combination of analytical approaches to fulfill the various needs of these 3 analytical communities.

Allergens↗
PubMed2003

Determination of ochratoxin A in foods: state-of-the-art and analytical challenges.

Ochratoxin A (OTA) can occur in a large variety of commodities (cereals, beans, groundnuts, spices, dried fruits, coffee, beer, wine) and, because of a carry-over effect, in milk, pig blood, liver, and kidney, and poultry meat from animals fed with contaminated feed. Because of the persistence of OTA in the food chain, exposure to the compound is a potential human health hazard. This has prompted adoption of regulatory limits in several countries which, in turn, implies the development of suitable validated and official analytical methods and rapid screening tests for cost-effective food control on a large scale. Liquid chromatography with fluorescence detection (LC-FLD), coupled with immunoaffinity column (IAC) clean-up, is the most widely employed analytical technique. LC coupled with electrospray-ionization mass spectrometry (MS) has detection limits comparable with those of LC-FLD and the selectivity of IAC can be achieved by tandem (MS-MS) or sequential (MS(n)) detection. Synthetic counterparts to natural antibodies in the form of molecularly imprinted polymers seem a promising alternative to IAC for sample preparation. New analytical approaches to rapid, low-cost screening methods, for example those based on biosensors and dip-stick-like kits, are a direction in which innovation can be expected. Analytical methods for evaluation of the occurrence of OTA in foods, human exposure, and risk assessment are critically reviewed.

Animals↗