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PubMed1991

Using empirical Bayes methods in biopharmaceutical research.

A compound sampling model, where a unit-specific parameter is sampled from a prior distribution and then observed are generated by a sampling distribution depending on the parameter, underlies a wide variety of biopharmaceutical data. For example, in a multi-centre clinical trial the true treatment effect varies from centre to centre. Observed treatment effects deviate from these true effects through sampling variation. Knowledge of the prior distribution allows use of Bayesian analysis to compute the posterior distribution of clinic-specific treatment effects (frequently summarized by the posterior mean and variance). More commonly, with the prior not completely specified, observed data can be used to estimate the prior and use it to produce the posterior distribution: an empirical Bayes (or variance component) analysis. In the empirical Bayes model the estimated prior mean gives the typical treatment effect and the estimated prior standard deviation indicates the heterogeneity of treatment effects. In both the Bayes and empirical Bayes approaches, estimated clinic effects are shrunken towards a common value from estimates based on single clinics. This shrinkage produces more efficient estimates. In addition, the compound model helps structure approaches to ranking and selection, provides adjustments for multiplicity, allows estimation of the histogram of clinic-specific effects, and structures incorporation of external information. This paper outlines the empirical Bayes approach. Coverage will include development and comparison of approaches based on parametric priors (for example, a Gaussian prior with unknown mean and variance) and non-parametric priors, discussion of the importance of accounting for uncertainty in the estimated prior, comparison of the output and interpretation of fixed and random effects approaches to estimating population values, estimating histograms, and identification of key considerations in the use and interpretation of empirical Bayes methods.

Bayes Theorem↗
PubMed1994

Empirical Bayes methods for stabilizing incidence rates before mapping.

The epidemiologic utility of mapping and ranking incidence rates is often questioned owing to instability of the observed incidence values in areas with small populations. Spurious fluctuations in the observed rates caused by this instability can mask true spatial and temporal trends in risk. To produce maps with the required level of geographic resolution, yet based on reliable estimates, it is desirable to reduce the random variation in the observed rates before mapping. In this paper, we describe the empirical Bayes approach for obtaining stabilized incidence estimates. We begin by deriving Bayes rate estimators and then illustrate how using the observed rates to estimate unknown distributional information leads to the empirical Bayes formulation. A drawback of the approach is that the histogram of the empirical Bayes rate estimates may be narrower than the true distribution of risk. We outline a constrained empirical Bayes approach that produces improved estimators for the true distribution of the unknown rates. We include discussions of relevant previous applications of empirical Bayes methods to rate mapping problems and an evaluation of the strengths and weaknesses of the approach.

Bayes Theorem↗
PubMed2001

Making the most of sparse clinical data by using a predictive-model-based analysis, illustrated with a stavudine pharmacokinetic study.

A small-scale clinical investigation was done to quantify the penetration of stavudine (D4T) into cerebrospinal fluid (CSF). A model-based analysis estimates the steady-state ratio of AUCs of CSF and plasma concentrations (R(AUC)) to be 0.270, and the mean residence time of drug in the CSF to be 7.04 h. The analysis illustrates the advantages of a causal (scientific, predictive) model-based approach to analysis over a noncausal (empirical, descriptive) approach when the data, as here, demonstrate certain problematic features commonly encountered in clinical data, namely (i) few subjects, (ii) sparse sampling, (iii) repeated measures, (iv) imbalance, and (v) individual design variation. These features generally require special attention in data analysis. The causal-model-based analysis deals with features (i) and (ii), both of which reduce efficiency, by combining data from different studies and adding subject-matter prior information. It deals with features (iii)--(v), all of which prevent 'averaging' individual data points directly, first, by adjusting in the model for interindividual data differences due to design differences, secondly, by explicitly differentiating between interpatient, interoccasion, and measurement error variation, and lastly, by defining a scientifically meaningful estimand (R(AUC)) that is independent of design.

Anti-HIV Agents↗
PubMed2004

Pulse oximetry theory and calibration for low saturations.

Pulse oximetry is a widely used technique in biomedical optics, but currently available pulse oximeters rely on empirical calibration approaches, which perform poorly at low saturations. We present an exact solution for pulse oximetry and show how this can be used as the basis for the development of a semiempirical calibration approach that may be useful, especially at low saturations and variable probe geometries. This new approach was experimentally tested against traditional empirical calibration techniques on transmission pulse oximetry for monitoring of fetal sheep using a minimally invasive spiral probe. The results open the way for the development of more accurate pulse oximetry.

Animals↗
PubMed2000

Dynamics of proteins predicted by molecular dynamics simulations and analytical approaches: application to alpha-amylase inhibitor.

The dynamics of alpha-amylase inhibitors has been investigated using molecular dynamics (MD) simulations and two analytical approaches, the Gaussian network model (GNM) and anisotropic network model (ANM). MD simulations use a full atomic approach with empirical force fields, while the analytical approaches are based on a coarse-grained single-site-per-residue model with a single-parameter harmonic potential between sufficiently close (r </= 7 A) residue pairs. The major difference between the GNM and the ANM is that no directional preferences can be obtained in the GNM, all residue fluctuations being theoretically isotropic, while ANM does incorporate directional preferences. The dominant modes of motions are identified by (i) the singular value decomposition (SVD) of the MD trajectory matrices, and (ii) the similarity transformation of the Kirchhoff matrices of inter-residue contacts in the GNM or ANM. The mean-square fluctuations of individual residues and the cross-correlations between domain movements retain the same characteristics, in all approaches-although the dispersion of modes and detailed amplitudes of motion obtained in the ANM conform more closely with MD results. The major weakness of the analytical approaches appears, on the other hand, to be their inadequacy to account for the anharmonic motions or multimeric transitions driven by the slowest collective mode observed in MD. Such motions usually suffer, however, from MD sampling inefficiencies, and multiple independent runs should be tested before making conclusions about their validity and detailed mechanisms. Overall this study invites attention to (i) the robustness of the average properties (mean-square fluctuations, cross-correlations) controlled by the low frequency motions, which are invariably reproduced in all approaches, and (ii) the utility and efficiency of the ANM, the computational time cost of which is of the order of "minutes" (real time), as opposed to "days" for MD simulations. Proteins 2000;40:512-524.

Computer Simulation↗
PubMed2005

Are psychodynamic and psychoanalytic therapies effective?: A review of empirical data.

There is a need for empirical outcome research in psychodynamic and psychoanalytic therapy. However, both the approach of empirically supported therapies (EST) and the procedures of evidence-based medicine (EBM) have severe limitations making randomised controlled trials (RCTs) an absolute standard. After a critical discussion of this approach, the author reviews the empirical evidence for the efficacy of psychodynamic psychotherapy in specific psychiatric disorders. The review aims to identify for which psychiatric disorders RCTs of specific models of psychodynamic psychotherapy are available and for which they are lacking, thus providing a basis for planning further research. In addition, results of process research of psychodynamic psychotherapy are presented. As the methodology of RCTs is not appropriate for psychoanalytic therapy, effectiveness studies of psychoanalytic therapy are reviewed as well. Studies of psychodynamic psychotherapy published between 1960 and 2004 were identified by a computerised search using Medline, PsycINFO and Current Contents. In addition, textbooks and journal articles were used. Twenty-two RCTs were identified of which 64% had not been included in the 1998 report by Chambless and Hollon. According to the results, for the following psychiatric disorders at least one RCT providing evidence for the efficacy of psychodynamic psychotherapy was identified: depressive disorders (4 RCTs), anxiety disorders (1 RCT), post-traumatic stress disorder (1 RCT), somatoform disorder (4 RCTs), bulimia nervosa (3 RCTs), anorexia nervosa (2 RCTs), borderline personality disorder (2 RCTs), Cluster C personality disorder (1 RCT), and substance-related disorders (4 RCTs). According to results of process research, outcome in psychodynamic psychotherapy is related to the competent delivery of therapeutic techniques and to the development of a therapeutic alliance. With regard to psychoanalytic therapy, controlled quasi-experimental effectiveness studies provide evidence that psychoanalytic therapy is (1) more effective than no treatment or treatment as usual, and (2) more effective than shorter forms of psychodynamic therapy. Conclusions are drawn for future research.

Empirical Research↗
PubMed1996

A professional response to demands for accountability: practical recommendations regarding ethical aspects of patient care. Working Group on Accountability.

Forceful new demands for accountability in medicine are arising from many interested parties. To maintain professional standards, physicians need to establish which demands are desirable and which are not. We adopt a model of stratified accountability that includes three major components: the accountable parties, the subject matter, and the processes for accountability. To begin describing the model, we focus on physicians and health care institutions. We focus on the ethical dimensions of medical practice, both because the difficulty of measuring such behaviors makes this a test case for accountability and because of the importance of ethical standards in maintaining patient trust. We first identify eight widely endorsed content areas for accountability in ethical conduct: medical decision making, confidentiality, fiduciary obligations (including conflicts of interest), responsibilities arising from patient vulnerability, personal standards, equity among patients, cultural representation, and procedures for resolving dilemmas. We then identify the currently most valid and reliable methods for assessing conduct: surveys among all involved parties, testing methods used for accreditation, limited audits, publication of policy, and careful use of report cards. A prototypical survey and report card are illustrated. However, we also note the need for improved accountability assessment methods. We next identify mechanisms for taking responsibility: sharing information, exchanging perspectives, making adjustments, and enforcing standards when necessary. Finally, because this report only begins to describe a small part of the accountability model, we urge explicit identification and development of professional standards for accountability in the many other areas of medicine.

Clinical Competence↗
PubMed2006

Uncertainty analysis in matched-field geoacoustic inversions.

Quantifying uncertainty for parameter estimates obtained from matched-field geoacoustic inversions using a Bayesian approach requires estimation of the uncertainties in the data due to ambient noise as well as modeling errors. In this study, the variance parameter of the Gaussian error model, hereafter called error variance, is assumed to describe the data uncertainty. In practice, this parameter is not known a priori, and choosing a particular value is often difficult. Hence, to account for the uncertainty in error variance, several methods are introduced for implementing both the full and empirical Bayesian approaches. A full Bayesian approach that permits uncertainty of the error variance to propagate through the parameter estimation processes is a natural way of incorporating the uncertainty of error variance. Due to the large number of unknown parameters in the full Bayesian uncertainty analysis, an alternative, the empirical Bayesian approach, is developed, in which the posterior distributions of model parameters are conditioned on a point estimate of the error variance. Comparisons between the full and empirical Bayesian inferences of model parameters are presented using both synthetic and experimental data.

Journal Article↗
PubMedDate not supplied

Chemically defined media and the culture of mammalian preimplantation embryos: historical perspective and current issues.

Considerable advances in media development for the culture of preimplantation mammalian embryos have been made since mouse embryos were first cultured and successfully transferred to foster mothers. The purpose of this review is to detail the history of the development of chemically defined media for the culture of preimplantation embryos. Two approaches have been used to determine the composition of chemically defined media: the 'back-to-nature' approach and 'let the embryo choose' or empirical optimization approach. Recent developments, including the supplementation of media with amino acids and the use of sequential media for the extended culture of preimplantation embryos, are critically assessed. Importantly, it is recognized that even the best media currently used are not optimal and inevitably cause imbalances and stress to the embryos. Consequently, preimplantation embryos must adapt to the culture environment in order to survive. The adaptations to stress that occur when embryos are placed in a chemically defined environment are reviewed. The implications of these various stresses on the patterns of gene expression in the early embryo and their potential long-term effects are also emphasized. The scientific and ethical issues raised by the commercialization of human embryo culture media are briefly addressed.

Adaptation, Physiological↗
PubMed2001

Trust in physicians and medical institutions: what is it, can it be measured, and does it matter?

Despite the profound and pervasive importance of trust in medical settings, there is no commonly shared understanding of what trust means, and little is known about what difference trust actually makes, what factors affect trust, and how trust relates to other similar attitudes and behaviors. To address this gap in understanding, the emerging theoretical, empirical, and public policy literature on trust in physicians and in medical institutions is reviewed and synthesized. Based on this review and additional research and analysis, a formal definition and conceptual model of trust is presented, with a review of the extent to which this model has been confirmed by empirical studies. This conceptual and empirical understanding has significance for ethics, law, and public policy.

Confidentiality↗
PubMed1995

Empirically based assessment and taxonomy of psychopathology: cross-cultural applications. A review.

This paper provides an overview of empirically based assessment and taxonomy, as illustrated by cross-cultural research on psychopathology. The empirically based approach uses standardized assessment procedures to score behavioral and emotional problems from which syndromes are derived by multivariate analyses. Items and syndromes are scored quantitatively to reflect the degree to which individuals manifest them, as reported by particular informants. Although the approach to assessing problems and to constructing taxonomic groupings differs from the ICD/DSM approach, there are no inherent contradictions between either their models for disorders nor the criterial features used to define disorders. Cross-cultural comparisons have yielded relatively small differences in problem rates and syndrome structure, plus considerable similarity in associations of problems with sex and SES, as well as similar correlations between reports by different types of informants. Research on variations in problems in relation to culture, sex, age, SES, and type of informant can contribute to improving both the ICD/DSM and empirically based approaches and to a more effective synthesis between them.

Adolescent↗
PubMed1993

The educational philosophies behind the medical humanities programs in the United States: an empirical assessment of three different approaches to humanistic medical education.

This study investigates the three major educational philosophies behind the medical humanities programs in the United States. It summarizes the characteristics of the Cultural Transmission Approach, the Affective Developmental Approach, and the Cognitive Developmental Approach. A questionnaire was sent to 415 teachers of medical humanities asking for their perceptions of the amount of time and effort devoted by their programs to these three philosophical approaches. The 234 responses constituted a 54.6% return. The approximately 80:20 gender ratio of males to females and other demographic data on age and educational background were consistent with other studies of the field of medical humanities. Reflections on the results in Table II indicate that some changes need to take place in the teaching of the medical humanities if the perceived ideal is to be achieved. In order for the current teachers of the medical humanities to think that the appropriate philosophies behind the teaching of the medical humanities are being implemented as they should be, much less time and effort need to be devoted to the Cultural Transmission Approach. With no other published reports on the educational philosophies behind the medical humanities programs, this study created a new knowledge base about this relatively young and rapidly emerging field.

Education, Medical↗
PubMed2004

Toward a typology of confidentiality breaches in health care communication: an ethic of care analysis of provider practices and patient perceptions.

Confidentiality should be a fundamental right of patients in a health care setting. However, health care providers who take an oath to uphold confidentiality often neglect this basic patient right. Breaching confidential health information is a serious ethical problem and a communication issue that, historically, has received limited empirical, theoretical, or practical attention. The goals of this project were to frame this issue from an ethic of care perspective, define the concept of a confidentiality breach, identify the types of confidentiality breaches being communicated in health care organizations, and understand how patients perceive these breaches. Based on interviews with 51 patients and observations of health care providers, a definition and typology of confidentiality breaches emerged. Theoretical and practical implications also became evident.

Adult↗
PubMed2004

Autonomy gone awry: a cross-cultural study of parents' experiences in neonatal intensive care units.

This paper examines parents' experiences of medical decision-making and coping with having a critically ill baby in the Neonatal Intensive Care Unit (NICU) from a cross-cultural perspective (France vs. U.S.A.). Though parents' experiences in the NICU were very similar despite cultural and institutional differences, each system addresses their needs in a different way. Interviews with parents show that French parents expressed overall higher satisfaction with the care of their babies and were better able to cope with the loss of their child than American parents. Central to the French parents' perception of autonomy and their sense of satisfaction were the strong doctor-patient relationship, the emphasis on medical certainty in prognosis versus uncertainty in the American context, and the "sentimental work" provided by the team. The American setting, characterized by respect for parental autonomy, did not necessarily translate into full parental involvement in decision-making, and it limited the rapport between doctors and parents to the extent of parental isolation. This empirical comparative approach fosters a much-needed critique of philosophical principles by underscoring, from the parents' perspective, the lack of "emotional work" involved in the practice of autonomy in the American unit compared to the paternalistic European context. Beyond theoretical and ethical arguments, we must reconsider the practice of autonomy in particularly stressful situations by providing more specific means to cope, translating the impersonal language of "rights" and decision-making into trusting, caring relationships, and sharing the responsibility for making tragic choices.

Academic Medical Centers↗
PubMed2005

Will the "real boy" please behave: dosing dilemmas for parents of boys with ADHD.

The use of Ritalin and other stimulant drug treatments for attention-deficit hyperactivity disorder (ADHD) raises distinctive moral dilemmas for parents; these moral dilemmas have not been adequately addressed in the bioethics literature. This paper draws upon data from a qualitative empirical study to investigate parents' use of the moral ideal of authenticity as part of their narrative justifications for dosing decisions and actions. I show that therapeutic decisions and actions are embedded in valued cultural ideals about masculinity, self-actualization and success, as well as in moral conceptions of authenticity and personal freedom. I argue that this investigation of parents' moral justifications and dosing dilemmas raises questions about the validity of authenticity as a transcendent moral principle. Moreover, this study demonstrates that in order to be relevant, bioethical analysis of neurocognitive enhancement must engage with ground-up studies of moral principles and decision-making in context.

Adolescent↗