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At least 505 records · Page 28Linked to original sources
PubMed2005

From complexity to category: responding to diagnostic uncertainties of autistic spectrum disorders.

OBJECTIVE: Recent data from Education Queensland has identified rising numbers of children receiving diagnoses of autistic spectrum disorder (ASD). Faced with funding diagnostic pressures, in clinical situations that are complex and inherently uncertain, it is possible that specialists err on the side of a positive diagnosis. This study examines the extent to which possible overinclusion of ASD diagnosis may exist in the presence of uncertainty and factors potentially related to this practice in Queensland. METHODS: Using anonymous self-report, all Queensland child psychiatrists and paediatricians who see paediatric patients with development/behavioural problems were surveyed and asked whether they had ever specified an ASD diagnosis in the presence of diagnostic uncertainty. Using logistic regression, elicited responses to the diagnostic uncertainty questions were related to other clinical- and practice-related characteristics. RESULTS: Overall, 58% of surveyed psychiatrists and paediatricians indicated that, in the face of diagnostic uncertainty, they had erred on the side of providing an ASD diagnosis for educational ascertainment and 36% of clinicians had provided an autism diagnosis for Carer's Allowance when Centrelink diagnostic specifications had not been met. CONCLUSION: In the absence of definitive biological markers, ASD remains a behavioural diagnosis that is often complex and uncertain. In response to systems that demand a categorical diagnostic response, specialists are providing ASD diagnoses, even when uncertain. The motivation for this practice appears to be a clinical risk/benefit analysis of what will achieve the best outcomes for children. It is likely that these practices will continue unless systems change eligibility to funding based on functional impairment rather than medical diagnostic categories.

Autistic Disorder↗
PubMed2005

Combining quantitative and qualitative measures of uncertainty in model-based environmental assessment: the NUSAP system.

This article discusses recent experiences with the Numeral Unit Spread Assessment Pedigree (NUSAP) system for multidimensional uncertainty assessment, based on four case studies that vary in complexity. We show that the NUSAP method is applicable not only to relatively simple calculation schemes but also to complex models in a meaningful way and that NUSAP is useful to assess not only parameter uncertainty but also (model) assumptions. A diagnostic diagram can be used to synthesize results of quantitative analysis of parameter sensitivity and qualitative review (pedigree analysis) of parameter strength. It provides an analytic tool to prioritize uncertainties according to quantitative and qualitative insights in the limitations of available knowledge. We show that extension of the pedigree scheme to include societal dimensions of uncertainty, such as problem framing and value-laden assumptions, further promotes reflexivity and collective learning. When used in a deliberative setting, NUSAP pedigree assessment has the potential to foster a deeper social debate and a negotiated management of complex environmental problems.

Computer Simulation↗
PubMed2003

Parental uncertainty and posttraumatic stress in serious childhood illness.

PURPOSE: To explicate the link between parental uncertainty and posttraumatic stress as a way to stimulate advancement in the design and evaluation of nursing interventions for parents of children with serious illness. METHODS: The literature on Mishel's uncertainty in illness theory and its reconceptualization--parental uncertainty in serious childhood illness--and posttraumatic stress are reviewed and synthesized. Pertinent methodological and sociocultural issues are discussed. CONCLUSIONS: The literature indicates support for the theoretical link between parental uncertainty and posttraumatic stress. This linkage provides direction for the design and evaluation of nursing interventions to support parents of children with serious childhood illness.

Catastrophic Illness↗
PubMedDate not supplied

Uncertainty estimation of pathlines in ground water models.

A method is proposed to estimate the uncertainty of the location of pathlines in two-dimensional, steady-state confined or unconfined flow in aquifers due to the uncertainty of the spatially variable unconditional hydraulic conductivity or transmissivity field. The method is based on concepts of the semianalytical first-order theory given in Stauffer et al. (2002, 2004), which allows estimates of the lateral second moment (variance) of the location of a moving particle. However, this method is reformulated in order to account for nonuniform recharge and nonuniform aquifer thickness. One prominent application is the uncertainty estimation of the catchment of a pumping well by considering the boundary pathlines starting at a stagnation point. In this method, the advective transport of particles is considered, based on the velocity field. In the case of a well catchment, backtracking is applied by using the reversed velocity field. Spatial variability of hydraulic conductivity or transmissivity is considered by taking into account an isotropic exponential covariance function of log-transformed values with parameters describing the variance and correlation length. The method allows postprocessing of results from ground water models with respect to uncertainty estimation. The code PPPath, which was developed for this purpose, provides a postprocessing of pathline computations under PMWIN, which is based on MODFLOW. In order to test the methodology, it was applied to results from Monte Carlo simulations for catchments of pumping wells. The results correspond well. Practical applications illustrate the use of the method in aquifers.

Models, Theoretical↗
PubMed2005

The nature of medical evidence and its inherent uncertainty for the clinical consultation: qualitative study.

OBJECTIVE: To describe how clinicians deal with the uncertainty inherent in medical evidence in clinical consultations. DESIGN: Qualitative study. SETTING: Clinical consultations related to hormone replacement therapy, bone densitometry, and breast screening in seven general practices and three secondary care clinics in the UK NHS. PARTICIPANTS: Women aged 45-64. RESULTS: 45 of the 109 relevant consultations included sufficient discussion for analysis. The consultations could be categorised into three groups: focus on certainty for now and this test, with slippage into general reassurance; a coherent account of the medical evidence for risks and benefits, but blurring of the uncertainty inherent in the evidence and giving an impression of certainty; and acknowledging the inherent uncertainty of the medical evidence and negotiating a provisional decision. CONCLUSION: Strategies health professionals use to cope with the uncertainty inherent in medical evidence in clinical consultations include the use of provisional decisions that allow for changing priorities and circumstances over time, to avoid slippage into general reassurance from a particular test result, and to avoid the creation of a myth of certainty.

Bone Density↗
PubMed2006

Uncertainty, responsibility, and the evolution of the physician/patient relationship.

The practice of evidence based medicine has changed the role of the physician from information dispenser to gatherer and analyser. Studies and controlled trials that may contain unknown errors, or uncertainties, are the primary sources for evidence based decisions in medicine. These sources may be corrupted by a number of means, such as inaccurate statistical analysis, statistical manipulation, population bias, or relevance to the patient in question. Regardless of whether any of these inaccuracies are apparent, the uncertainty of their presence in physician information should be disclosed to the patient. These uncertainties are not, however, shared by physicians with patients, and have caused a direct increase in patient responsibilities and mistrust. Only when disclosure of uncertainty becomes commonplace in medical practice will the physician/patient relationship evolve to a level of greater understanding and satisfaction for both the physician and patient.

Attitude of Health Personnel↗
PubMed2006

The UK Food Standards Agency draft report on variability and uncertainty in toxicology: a response by FRAME.

At the request of the Food Standards Agency, the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) established a Working Group on Variation and Uncertainty in Toxicology (WG VUT). In April 2006, the WG VUT produced a draft report for public consultation. FRAME made a submission in response to this consultation in July 2006. We commend the WG VUT for its comprehensive account of many of the problems associated with risk assessment, and for making recommendations about the problems that need to be addressed. We were particularly encouraged by the WG VUTs recognition of the need for guidelines on how toxicological studies should be conducted and data analysed. However, we believe that the report has not achieved all of its objectives. It does not adequately consider how modern technologies, experimental design, statistical analysis and species extrapolation can be used in practice to address variability and uncertainty. There is a disproportionate focus on the sources of variability and uncertainty in human data, with relatively little consideration of how variation and uncertainty due to animal tests can be addressed. Furthermore, it is clear that, until the advantages and limitations of all toxicological methods are fully appraised and testing strategies and guidelines are agreed, the scope for improving the existing approaches to risk assessment will be severely limited. Hence, the use of alternative methods for hazard identification and characterisation merit more consideration than they were given in the draft report.

Animals↗
PubMed2006

Uncertainty and 'technological horizon' in qualitative interviews about HIV treatment.

Highly Active Anti-Retroviral Treatment (HAART) has reduced death and morbidity among people with HIV. However, HAART is not always effective, can produce serious side-effects and implies uncertainty for patients. To address HAART-related uncertainty, 20 qualitative interviews were conducted with gay men with HIV in Glasgow and London. The interviewees were purposively selected to reflect diversity in terms of year of diagnosis, experiences of illness and treatment-related side-effects. The interviews were analysed using the constant comparison method to derive themes. Among those using HAART, analysis identified themes of 'good health', 'illness' and 'loss of confidence'. Uncertainty was managed through a discourse of 'technological horizon' that combined the ongoing innovations of HAART and biographical time. These themes are discussed in terms of the implications for HIV care. In particular, technological horizon provides a basis for the management of uncertainty in the prescribing relationship between patient and clinician.

Adult↗
PubMed2006

LS-NMF: a modified non-negative matrix factorization algorithm utilizing uncertainty estimates.

BACKGROUND: Non-negative matrix factorisation (NMF), a machine learning algorithm, has been applied to the analysis of microarray data. A key feature of NMF is the ability to identify patterns that together explain the data as a linear combination of expression signatures. Microarray data generally includes individual estimates of uncertainty for each gene in each condition, however NMF does not exploit this information. Previous work has shown that such uncertainties can be extremely valuable for pattern recognition. RESULTS: We have created a new algorithm, least squares non-negative matrix factorization, LS-NMF, which integrates uncertainty measurements of gene expression data into NMF updating rules. While the LS-NMF algorithm maintains the advantages of original NMF algorithm, such as easy implementation and a guaranteed locally optimal solution, the performance in terms of linking functionally related genes has been improved. LS-NMF exceeds NMF significantly in terms of identifying functionally related genes as determined from annotations in the MIPS database. CONCLUSION: Uncertainty measurements on gene expression data provide valuable information for data analysis, and use of this information in the LS-NMF algorithm significantly improves the power of the NMF technique.

Algorithms↗
PubMed2004

Estimate of uncertainty of measurement from a single-laboratory validation study: application to the determination of lead in blood.

BACKGROUND: Lead is an environmental pollutant, and human exposure is assessed by monitoring lead concentrations in blood. Because the main source of environmental exposure has been the use of leaded gasoline, its phase-out has led to decreased lead concentrations in the general population. Therefore, validated analytical methods for the determination of lower lead concentrations in blood (<150 microg/L) are needed. In addition, new ISO standards require that laboratories determine and specify the uncertainty of their results. METHODS: We validated a method to determine lead in blood at concentrations up to 150 microg/L by electrothermal atomic absorption spectrometry with Zeeman background correction according to EURACHEM guidelines. Blood samples were diluted (1:1 by volume) with 2 mL/L Triton X-100. NH4H2PO4 (5 g/L) and Mg(NO3)2 (0.5 g/L) were used as modifiers. Matrix-matched standards were used for calibration. RESULTS: We determined the limits of detection (3.1 microg/L) and quantification (9.4 microg/L). Repeatability and intermediate imprecision within the range 35-150 microg/L were <5.5% and <6.0%, respectively. We assessed trueness by use of certified reference materials, by recovery tests, and by comparison with target values of other reference materials (candidate external quality assessment samples). The expanded uncertainty ranged from 20% to 16% (with a confidence level of 95%) depending on concentration. CONCLUSIONS: This study provides a working example of the estimate of uncertainty from method performance data according to the EURACHEM/CITAC guidelines. The estimated uncertainty is compatible with quality specifications for the analysis of lead in blood adopted in the US and the European Union.

Environmental Pollutants↗
PubMed2003

Advantages of using the net-benefit approach for analysing uncertainty in economic evaluation studies.

No consensus has yet been reached on how to analyse uncertainty in economic evaluation studies where individual patient data are available for costs and health effects. This paper summarises the available results regarding the analysis of uncertainty on the cost-effectiveness plane and argues for using the net-benefit approach when analysing uncertainty in cost-effectiveness studies. The net-benefit approach avoids the interpretation and statistical problems related to the incremental cost effectiveness ratio and implies several advantages. First, traditional statistical methods can be used for confidence-interval estimation and hypothesis testing. Second, calculation of the optimal sample size and the power of the study are facilitated allowing the correlation between costs and effects to vary within and between patient groups. Third, the use of a Bayesian approach to cost-effectiveness analysis is facilitated. Fourth, a formal relation between cost-effectiveness acceptability curves and statistical inference is provided. Finally, the net-benefit approach gives the Fieller's limits of the confidence interval for the incremental cost-effectiveness ratio in the cost-effectiveness plane. Based on these advantages the net-benefit approach should strongly be considered when analysing uncertainty in cost-effectiveness analyses.

Bayes Theorem↗
PubMed2005

Incorporation of uncertainty in health economic modelling studies.

In a recent leading article in PharmacoEconomics, Nuijten described some methods for incorporating uncertainty into health economic models and for utilising the information on uncertainty regarding the cost effectiveness of a therapy in resource allocation decision-making. His proposals are found to suffer from serious flaws in statistical and health economic reasoning.Nuijten's suggestions for incorporating uncertainty: (a) wrongly interpret the p-value as the probability that the null hypothesis is true; (b) represent this probability wrongly by truncating the input distribution; and (c) in the specific example of an antiparkinsonian drug uses a completely inappropriate p-value of 0.05 when the null hypothesis would, in reality, be emphatically disproved by the data.His suggestions regarding minimum important differences in cost effectiveness: (a) introduce areas of indifference that suggest inappropriate reliance on cost minimisation while failing to recognise that decisions should be based on expected costs versus benefits; and (b) offer no guidance on how the probabilities associated with these areas could be used in decision-making. Furthermore, Nuijten's model for Parkinson's disease is over-simplified to the point of providing a bad example of modelling practice, which may mislead the readers of PharmacoEconomics. The rationale for this paper is to ensure that readers do not apply inappropriate analyses as a result of following the proposals contained in Nuijten's paper. In addition to a detailed critique of Nuijten's proposals, we provide brief summaries of the currently accepted best practice in cost-effectiveness decision-making under uncertainty.

Antiparkinson Agents↗
PubMedDate not supplied

Is the NHS willing to help clinicians and patients reduce uncertainties about the effects of treatments?

Uncertainty is an inevitable component of clinical practice. Clinicians have a responsibility to minimise it by keeping up-to-date with current knowledge: but what is the responsibility of individual clinicians in reducing collective uncertainty? In all fields of medicine there are important questions relevant to both patients and clinicians, which can be answered only by clinical research. Unfortunately, much of the clinical research that attracts funding does not address the questions that both patients and clinicians regard as important. Furthermore, although the NHS has a proud record of innovation and clinical research, recent changes are jeopardising the ability and willingness of NHS clinicians to continue undertaking such work. A combination of increased bureaucracy in obtaining research ethics and local research and development (R&D) governance approval and the pressures on management to deliver service targets threaten to strangle research by NHS clinicians. Policy makers argue for informed patient choice, modernisation and improved quality. It is not in the interest of patients when research designed to address important therapeutic uncertainties is seen as an optional extra, rather than an intrinsic element of a health service interested in improving quality. The NHS needs to listen to its users, ie the patients, and to its clinical staff, and to encourage them to engage in research to help reduce those uncertainties.

Clinical Competence↗
PubMed1991

The effects of uncertainty on the physician-patient relationship in predictive genetic testing.

In this commentary, I wish to focus on the physician as teacher and communicator. How will physicians deal candidly with their patients in the face of multiple sources of uncertainty? Will physicians recognize the extent of uncertainty? Are they prepared to? Disposed to? Failure to take advantage of a test that may significantly affect the health of an individual or the health of future offspring is a source of one possible disservice to patients. Failure to appreciate the magnitude of uncertainty in clinical testing may lead to other harms. Physicians are also called on to convey information and to aid understanding; individuals are at a disadvantage when this process is flawed by physicians' failure to appreciate uncertainty.

Biomedical Technology↗
PubMedDate not supplied

Uncertainty estimation in chemical measurements: carbon dioxide determination at atmospheric concentration.

The present work deals with the evaluation of measurement uncertainty in the determination of carbon dioxide (CO2) concentration in atmosphere, given the high relevance of this greenhouse gas that influences earth climate. In order to carry out CO2 measurements, non dispersive infrared (NDIR) analysers are usually employed as they are stable and scarcely affected by interferences from other air components or pollutants. Typical uncertainty sources are the resolution of the analyser, its time drift and the contributions due to instrument calibration, which is required in order to produce traceable measurement results. The calibration uncertainty takes into account the uncertainty of the composition of the calibration gas mixtures, the instrument repeatability and the possible or residual lack of fit of the adopted mathematical model.

Atmosphere↗
PubMed2004

Understanding medical uncertainty: a primer for physicians.

Many decisions in General Medicine have to be made in the paucity of well-researched information. Despite the existence of evidence-based guidelines, physicians may perceive obstacles in implementing these in clinical practice. Intolerance to uncertainty may result in a tendency to perceive ambiguous situations as sources of threat. Variability in treatment, choice of medical specialty, increased personal anxiety, increased test ordering tendencies, decrease comfort with geriatric and psychological problems have been correlated with intolerance to uncertainty. Various Instruments and scales are currently available to measure physician's uncertainty. Quantitative and qualitative techniques of managing uncertainty include shared decision-making, meticulous history-taking and evaluation, exclusion of worrisome diagnosis, ability to critically appraise current literature and establishing trust with patient.

Attitude of Health Personnel↗
PubMed2005

Experiences with the NUSAP system for multidimensional uncertainty assessment.

This paper discusses recent experiences with the NUSAP system for multidimensional uncertainty assessment, based on case studies that vary in complexity. We show that the NUSAP method, and especially the pedigree analysis part of it, is useful to assess not only parameter uncertainty but also to systematically reflect upon (model) assumptions and problem frames. A diagnostic diagram can be used to synthesize results of quantitative and qualitative analysis. It provides an analytic tool to prioritize uncertainties according to quantitative and qualitative insights in the limitations of available knowledge. We further show that extension of the pedigree scheme to include societal dimensions of uncertainty, such as problem framing and value-laden assumptions, further promotes reflexivity and collective learning. When used in a deliberative setting, NUSAP pedigree assessment has the potential to foster a deeper social debate and a negotiated management of complex environmental problems.

Decision Support Techniques↗
PubMed2005

Resources and uncertainties in evaluation of chemicals: basic methodological developments.

Conscious handling of uncertainty is critical in the assessment of chemicals, where the demand of knowledge is high compared to the available amount of resources. Consequently weighing between the use of resources and the acceptance of uncertainty has to be a transparent process and this sets up a challenge in relation to the application of mathematical methods. The maximum entropy principle is a useful paradigm for setting up prior information that is as non-informative as possible. It is shown how the use of partial ordering for deriving ranking results can be considered as a maximum entropy strategy in relation to the model structure uncertainty. In this way it seems possible to solve central parts of the problem of resource optimising risk assessment by combining the precautionary principle and screening before more detailed risk assessment is undertaken. The non-parametric approach of partial order technique further appears to be more transparent than most other ranking methodologies for complex systems. Because in the partial order techniques, no more or less known uncertainty will be hidden in the application of specific weighting factors and functional relationships among the criteria.

Environmental Exposure↗