The analysis of neuronal discharge sequences: change-point estimation and comparison of variances

A key problem in neurophysiology is to determine whether, after presentation of a stimulus, there has been a modification in the discharge of a recorded neuron and if so, an attempt is made to estimate the latency of the response. The estimation problem can be considered as that of the estimation of a change-point in a sequence of random variables. The gamma distribution is adequate to model the distribution of intervals between action potentials for different types of neurons. Simulations show that the maximum likelihood estimator based on this model is efficient and robust. An additional problem, in the case of experiments in which a movement follows the stimulus, is to determine whether a response is related to the stimulus or to the movement. A test based on the comparison of marginal scales of a bivariate distribution is proposed. The whole procedure has been tested in simulation and with real examples.     

Epizootics of Salmonella infection in poultry may be the result of modern selective breeding practices

This paper discussess the hypothesis that a major factor in the epizootics of Salmonella infection in poultry is a declining host genetic diversity. A computer model is described which is based on models that have been previously used to investigate host-pathogen coevolution in cereal crops. It is shown that, as host genetic diversity declines, parasite diversity also declines to a lower equilibrium level. With a highly diverse host, parasite numbers decline to zero. With a homogeneous host population, after an initial decline, there is a rapid increase in parasite numbers, due to the selection of a particularly well adapted parasite strain. This simple computer simulation is used as the basis for a discussion of the literature supporting the suggestion that a major factor in the epizootic of Salmonella in poultry is related to the low genetic diversity of commercial poultry flocks.     

The analysis of randomised controlled trial data with more than one follow-up measurement. A comparison between different approaches

When more than one follow-up measurement is analysed in a randomized controlled trial, there is no consensus how to analyse the overall intervention effect in a proper way. Mostly, longitudinal analysis of covariance is used, because with this method a correction is made for possible regression to the mean. However, in this paper it is shown that this method (mostly) leads to an overestimation of the intervention effect. A possible solution is the use of autoregression, although this does not seem to be the best solution, because it leads to an overcorrection. Due to these flaws, in this paper a new approach is introduced in which a correction for the baseline value is made for the first follow-up, but no correction is made for the remaining follow-up measurements.     

Analysis of case-cohort designs

The case-cohort design is most useful in analyzing time to failure in a large cohort in which failure is rare. Covariate information is collected from all failures and a representative sample of censored observations. Sampling is done without respect to time or disease status, and, therefore, the design is more flexible than a nested case-control design. Despite the efficiency of the methods, case-cohort designs are not often used because of perceived analytic complexity. In this article, we illustrate computation of a simple variance estimator and discuss model fitting techniques in SAS. Three different weighting methods are considered. Model fitting is demonstrated in an occupational exposure study of nickel refinery workers. The design is compared to a nested case-control design with respect to analysis and efficiency in a small simulation. In this example, case-cohort sampling from the full cohort was more efficient than using a comparable nested case-control design.     

Creating theory: Encouragement for using creativity and deduction in qualitative nursing research

Texts about theory in nursing often refer to theory construction by using inductive methods in a rigid way. In this paper, it is instead argued that theories are created, which is in line with most philosophers of science. Theory creation is regarded as a creative process that does not follow a specific method or logic. As in any creative endeavour, the inspiration for theory creation can come from many sources, including previous research and existing theory. The main idea put forward is that deductive qualitative research approaches should play a key role in theory creation. Furthermore, there is a need to differentiate between theory creation and theory justification. A model that emphasizes the creative aspects of theory creation and theory justification using qualitative approaches is presented. The model suggests that knowledge development is a deductive trial-and-error process where theory creation is followed by testing. Scientific theory creation and justification are presented as an iterative process that is deductive in that a testable hypothesis is derived from the theory. If the hypothesis is falsified, then the theory needs modification or might be altogether wrong. Several factors can block the creative process, both in theory development and in finding ways to test a theory in the justification phase. Some of these blockers are the idea of ‘building blocks’ and the inductive view of science often brought forward in nursing. Other blockers include striving for consensus and adherence to existing nursing philosophies and existing theories. Research and knowledge development are creative processes, and following predefined methods is not enough to ensure scientific rigour in qualitative nursing research.     

全自动红细胞沉降率智能分析仪的研究

血红细胞沉降是临床诊断中测试的一项重要参数，传统的魏氏法是一种手工测试方法且测试周期长，不适应大批量测试。快速的全自动红细胞沉降率分析仪的测试时间是魏氏法的一半，与魏氏法的相关性好，仪器经临床使用，测试稳定，效果良好。     

The predictive value of microbiologic diagnostic tests if asymptomatic carriers are present

If a proper gold standard is not available, then the predictive value of a test cannot be estimated. In this paper the concept of etiologic predictive value (EPV) is introduced. It is a quantity that will yield the predictive value of a test to predict presence of a specified disease in situations for which no proper gold standard is available. This is achieved by using information obtained from a healthy control population. This quantity requires that the marker in our test is present in all individuals having the specified disease, as in the case where the marker is the aetiologic factor for the specified disease. Furthermore this quantity requires that asymptomatic carriers are present. This means that not all individuals with the marker has the specified disease. EPV is developed with special reference to the evaluation of bacterial cultures, or rapid tests to detect a bacterium, but the quantity might be used in other circumstances as well. EPV is applied to an example in which conventional throat culture is evaluated. Further information concerning EPV can be found at http://www.infovice.se/fou/epv.     

Model averaging for robust extrapolation in evidence synthesis

Extrapolation from a source to a target, eg, from adults to children, is a promising approach to utilize external information when data are sparse. In the context of meta-analyses, one is commonly faced with a small number of studies, whereas potentially relevant additional information may also be available. Here, we describe a simple extrapolation strategy using heavy-tailed mixture priors for effect estimation in meta-analysis, which effectively results in a model-averaging technique. The described method is robust in the sense that a potential prior-data conflict, ie, a discrepancy between source and target data, is explicitly anticipated. The aim of this paper is to develop a solution for this particular application to showcase the ease of implementation by providing R  code, and to demonstrate the robustness of the general approach in simulations.     

‘Learning to play with new friends’: systematic quality development work in a leisure-time centre

This article explores the recontextualisation of systematic quality development work (Sqdw) in a leisure-time centre. Two teachers’ processes of planning, organisation, documentation and evaluation were investigated, the aim being to explore the recontextualisation of Sqdw in practice. The study is thus a case study of these teachers’ practice carried out through fieldwork and using different methods. The findings reveal a practice where play with play-boxes is used in a systematic process as a tool to make children's social learning visible. The teachers create possibilities for children's learning in a manner in accordance with a leisure-time tradition where social learning is documented and evaluated. A formal educational discourse is not enacted in this leisure-time centre; instead a social pedagogical approach is reproduced. Nevertheless, Sqdw is enacted and appears to help the teachers make visible their social pedagogical work in a new context.     

Test battery for assessing vascular disturbances of fingers

The diagnosis of vibration-induced white finger (VWF) is difficult, often relying on medical interview and history. The condition is characterized by an exaggerated vasoconstriction of digital arteries in response to cold. The complete closure of digital arteries is episodic and results in a characteristic blanching that is rarely observed by a clinician. Objective measurements of the response of the digital circulation to cold can assist in evaluating a patient for VWF. Finger systolic blood pressure (FSBP) following local cooling is a measure of cold-induced vasoconstriction in digital arteries and is an assessment of vasomotor tone. Low FSBPs following cooling are indicative of dysfunction. Finger skin temperature (FST) following hand cooling is a measure of cutaneous blood flow. The mechanism underlying the recovery of cutaneous blood flow following cooling is as yet not fully understood, but a delayed recovery is believed to arise from persistent vascular disturbances of the fingers or from a resulting in conflicting opinions concerning the utility of the measurements, a scarcity of comparable data from epidemiological investigations, and limited normative data to aid clinicians in decision-making. This review of evidence on which the tests are based is aimed at providing clinicians and researchers with an understanding of the factors that must be considered when conducting the tests, interpreting the results, and comparing results between different studies.     

Empowerment: A Conceptual Discussion

The concept of 'empowerment' is used frequently in a number of professional areas, from psychotherapy to social work. But even if the same term is used, it is not always clear if the concept denotes the same goals or the same practice in these various fields. The purpose of this paper is to clarify the discussion and to find a plausible and useful definition of the concept that is suitable for work in various professions. Several suggestions are discussed in the paper, for example control over life or health, autonomy, ability, self-efficacy, self-esteem, and freedom, and it is concluded that there are two plausible complementary uses, one as a goal and one as a process or approach. Empowerment as a goal is to have control over the determinants of one's quality of life, and empowerment as a process is to create a professional relation where the client or community takes control over the change process, determining both the goals of this process and the means to use.     

Radical nursing and the emergence of technique as healthcare technology

The integration of technology in care is core business in nursing and this role requires that we must understand and use technology informed by evidence that goes much deeper and broader than actions and behaviours. We need to delve more deeply into its complexity because there is nothing minor or insignificant about technology as a major influence in healthcare outcomes and experiences. Evidence is needed that addresses technology and nursing from perspectives that examine the effects of technology, especially related to increasing demands for efficiency, the relationship of technology to nursing and caring, and a range of philosophical questions associated with empowering people in their healthcare choices. Specifically, there is a need to confront in practice the ways technique influences care. Technique is the creation of a kind of thinking that is necessary for contemporary healthcare technology to develop and be applied in an efficient and rational manner. Technique is not an entity or specific thing, but rather a way of thinking that seeks to shape and organize nursing activity, and manage efficiently individual difference(s) in care. It emphasizes predetermined causal relationships, conformity, and sameness of product, process, and thought. In response is needed a radical vision of nursing that attempts in a real sense to ensure we meet the needs of individuals and their community. Activism and advocacy are needed, and a willingness to create a certain detachment from the imperatives that technique demands. It is argued that our responsibility as nurses is to respond in practice to the errors, advantages, difficulties, and temptations of technology for the benefit of those who most need our assistance and care.     

Analysis of testicular cancer data using a frailty model with familial dependence

Previously published papers have indicated a fairly strong familial dependence intesticular cancer patients. This is particularly evident in brothers. We have applied a frailty model with familial dependence to family data on brothers of testicular cancer patients from the Norwegian Radium Hospital. The model is a two-level frailty, with variation in susceptibility at both the family and the individual level. Specifically, the frailty variable is assumed to be compound Poisson distributed to allow individuals to be non-susceptible. The underlying Poisson parameter is gamma distributed to model how testicular cancer is distributed among families. This is an extension of a previous compound Poisson frailty model developed for individual testicular cancer data, and an alternative to traditional modelling of survival time family data. The likelihood construction and ascertainment problems are looked at in detail. To avoid ascertainment bias, the likelihood is based on the probability of observing the disease status for each brother in a family, given that at least one brother is ascertained. The estimated relative risk for brothers is 7.4. This paper expands on a previous analysis of the data by using a frailty model, which makes it possible to examine how the cancer is distributed among families. The estimated gamma-shaped parameter is 0.151 (95 per cent confidence interval 0.078-0.294), and this indicates that in order to obtain the high relative risks observed for brothers of testicular cancer patients, the distribution of susceptibility has to be strongly skewed among the families. The vast majority of families have a very low risk and a small proportion have a high risk. In addition, a quantity similar to the relative risk is derived to show that the susceptibility is skewly distributed also if the Poisson parameter is Bernoulli or stable distributed. This indicates that the results are valid also if other distributions are used to model familial dependence in the compound Poisson frailty model.     

Can a community development model be used for health programmes in an industrialized country?

Injury resulting from accident is a serious public health problem in Sweden, as it is in the rest of the world. Theoretically, almost all incidents can be prevented. However, in practice, injury-prevention is a complex problem. A community-level intervention programme for prevention of accidents was developed in the municipality of Sollentuna, Stockholm County. The primary strategy has been to involve the community through representatives as well as through local organizations and groups. Project organization has been built up in cooperation with the municipal primary health-care department, local authorities, voluntary organizations and citizen agencies. A common opinion is that it is the actual process in a community programme which is important, that alters the type of involvement from a ‘top-down’ to a ‘bottom-up’ approach. Can a local community take over responsibility for running such a programme which has been initiated by an external authority or organization? We think that, at least for Swedish circumstances, the community development approach is far too optimistic in its expectation that community members should and can stay actively involved in programme decisions. Based on our experience, it does not seem possible to maintain a broad self-sustained programme solely with input from community members.     

Inference of the Youden index and associated threshold using empirical likelihood for quantiles

The Youden index is a widely used measure in the framework of medical diagnostics, where the effectiveness of a biomarker (screening marker or predictor) for classifying a disease status is studied. When the biomarker is continuous, it is important to determine the threshold or cut-off point to be used in practice for the discrimination between diseased and healthy populations. We introduce two methods aimed at estimating the Youden index and its associated threshold. The first one is a modified version of a recent approach based on the delta method, and the second one is based on the adjusted empirical likelihood for quantiles in the setting of a two-sample problem. We also include CIs for both of them. In the simulation study, we compare both methods under different scenarios. Finally, a real example of prostatic cancer, well known in the literature, is analysed to provide the reader with a better understanding of the new methodology.     

A sequential design to estimate sensitivity and specificity of a diagnostic or screening test

We consider efficient study designs to estimate sensitivity and specificity of a candidate diagnostic or screening test. Our focus is the setting in which the candidate test is inexpensive to administer compared to evaluation of disease status, and the test results, available in a large cohort, can be used as a basis for sampling subjects for verification of disease status. We examine designs in which disease status is verified in a sample chosen so as to optimize estimation of either sensitivity or specificity. We then propose a sequential design in which the first step of sampling is conducted to efficiently estimate specificity. If the candidate test is determined to be of sufficient specificity, then step two of sampling is conducted to estimate sensitivity. We propose estimators based on this sequential sampling scheme, and show that the performance of these estimators is excellent. We develop sample size calculations for the sequential design, and show that this design, in most situations, compares favourably in terms of expected sample size to a fixed size design.     

Information, understanding and the benign order of everyday life in genetic counselling

Genetic counselling as a medical encounter is characterised by the centrality of the provision of information. Much of the counselling session is filled by information delivery about the symptoms, the prognosis and the transmission of the disease, the risks involved and the possibilities for genetic testing. The present paper is a study of how information is delivered in actual genetic counselling sessions. The data consist of 10 video-recorded sessions from a genetics clinic in Finland, and the methodology is based on conversation analysis. The paper focuses on the doctor's talk in a specific interactional context, the slot after a candidate understanding by a client. The analysis shows that the doctors have two basic orientations: they work towards securing correct understanding and they display being attuned to what the information means to the clients, particularly to whether it is positive or negative to them. The latter orientation is related to what has been called 'the benign order of everyday life' (Maynard 2003). The findings in the paper offer a possibility for a discussion about the principles and practices of genetic counselling.     

A computer program for application in epidemiological analysis

The importance of computer science as a working tool for the health sector is an unquestionable fact in any modern society.EPIDEMO, developed by the authors, can be defined as a set of programs whose main characteristic is its ability to process a given series of data in a totally integrated way, with an epidemiological and statistical approach.EPIDEMO is a program with a good relational database, which allows preliminary statistical analyses of data that can easily be expanded with more specific statistical options, and is compatible with other programs available on the market. It is a useful, accurate and versatile tool that meets the needs of health professionals in the field of epidemiological research.     

The resurgence of tuberculosis in the Republic of Ireland: Perceptions and reality

Tuberculosis remained a very significant cause of death in Ireland until the mid-20th century and still occupies a prominent position in the folk memory. As I show with reference to recent Irish media coverage, the global resurgence of tuberculosis is therefore viewed with concern in Ireland. Using data collated by the Health Protection Surveillance Centre between 1998 and 2005 however, I show that the recent increase in tuberculosis incidence in Ireland is less than is popularly perceived. This increase is largely associated with economic immigrants attracted to Ireland by the ‘Celtic Tiger’ economic boom, but there is little evidence to suggest that this has had a negative impact on the Irish-born population. Drug resistance is still a small but growing problem. Whilst vigilance is required, it is argued that the recent increase does not at present indicate a likely return to the situation in the mid-20th century.