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PubMed2004

[A correlative study of the uncertainty in the climacteric women].

The purpose of this study was to explore the relationship between climacteric symptoms, knowledge, and uncertainty in climacteric women. A cross-sectional correlational research design was used. Data were collected by face-to-face interview. The Greene Climacteric Scale, Health Knowledge about Menopause Scale, and Perceived Uncertainty Scale were used to assess data. A convenience sampling approach was used to enlist 70 female subjects who were mothers of students in a nursing college located in southern Taiwan and were in perimenopause or post-menopause. The results of the study indicated that levels of uncertainty on the part of the subjects toward the climacteric state were moderate. Subjects in the perimenopause period had significantly higher levels of uncertainty about the climacteric state than those in the post-menopause period. The levels of uncertainty were significantly negatively correlated with socio-economic status. The frequency and disturbance levels of climacteric symptoms among subjects were between "not at all" and "a little". The levels of uncertainty were significantly positively correlated with frequency of and disturbance caused by the symptoms. The score on the knowledge about menopause was below average and was significantly negatively correlated with uncertainty. The degree of disturbance caused by the symptoms, menopause status, and knowledge explain 34% of the variance in uncertainty. The findings of the study support the view that climacteric women who had fewer symptoms and more knowledge had lower levels of uncertainty. Nurses can develop interventions to reduce uncertainty in climacteric women.

Climacteric↗

PubMed2005

Uncertainty analysis of (99m)Tc-HEPIDA liver clearance determination.

BACKGROUND: The aim of the study was to obtain information on the accuracy and precision of (99m)Tc-HEPIDA hepatic (Cl(Hp)) and plasma (Cl(Pl)) clearances and selection of an appropriate estimator of the measurement uncertainty of a single determination of these quantities. MATERIAL AND METHODS: In a simulation (Monte Carlo) experiment, it was assumed that the recorded results of plasma and hepatic clearances, as obtained from 185 patients, provided authentic information about (99m)Tc-HEPIDA behaviour in the body over a wide range of the clearances studied. The time course (99m)Tc-HEPIDA concentration in blood plasma has been described by means of biexponential function with parameter values derived for each patient. For each patient, using these data and urinary excretion data, there had been 5000 simulations performed; in each of the latter, the directly measured numbers have been substituted by simulated ones, obtained by means of varying the real ones, using random generated values. These reflected errors of plasma and radioactive standard pipetting (from 1 to 5%) and stochasticity of counting radioactive decay (1%). The time of blood sampling and urine voiding was also varied, assuming realistic uncertainty. The varied values were then used for computation of the simulated clearances. From the 5,000 calculated clearances for each patient, mean-values were calculated, as well as mean standard errors, standard deviations and mean uncertainty of measurements using a widely accepted rule of partial error propagation, and, in addition, a modified rule of the latter. Accuracy of clearance (Cl(Pl), Cl(Hp), Cl(Ur)) determination was assessed on the basis of comparison of mean values from simulations with those from directly recorded values. Precision was identified with standard deviation of each of the 5000 simulations. The uncertainty thus obtained was compared with results of calculated traditional and modified uncertainty. There was good agreement between standard deviation of the simulations with results of the modified calculation of total differential. Therefore, a coefficient of variation from simulation computations and a modified means of calculation of the propagated errors was accepted as a measure of uncertainty of a single determination. RESULTS/CONCLUSIONS: There was a very high correlation between the mean values from simulations and those from direct determinations (r > 0.98 in each case). The regression lines practically corresponded to the lines of identity. These correlations were not affected by the assumed range of pipetting uncertainty. In conclusion, the methods of (99m)Tc-HEPIDA clearance determination are satisfactory. Precision of clearance measurements depends substantially upon uncertainty of pipetting. For plasma clearance, the coefficients of variations at Cl(Pl) > 350 ml/min and at ab.80 ml/min amounted to 2 and 11% respectively, at pipetting uncertainty of 2%. Similarly, for hepatic clearances of (99m)Tc-HEPIDA of 300 ml/min and 30 ml/min, CV was 2.5 and 25%, respectively (at the same uncertainty of pipetting).

Algorithms↗

PubMed2006

Investigating the construct validity of intolerance of uncertainty and its unique relationship with worry.

Although recent findings suggest that intolerance of uncertainty is a fundamental construct involved in excessive worry, additional research is required to further establish the construct validity of intolerance of uncertainty and demonstrate its unique contribution to the understanding of worry. The present study examined the relationships among measures of worry, intolerance of uncertainty, intolerance of ambiguity, perfectionism, and perceived control in a sample of 197 university students. The findings indicated that intolerance of uncertainty moderately overlaps with earlier conceptualizations of intolerance of ambiguity; however, worry was more highly related to intolerance of uncertainty than to intolerance of ambiguity. Intolerance of uncertainty also emerged as the most salient predictor of worry compared to other cognitive processes such as perfectionism and perceived control. Worry and intolerance of uncertainty continued to be significantly related after controlling for intolerance of ambiguity, perfectionism, and perceived control, which implies that intolerance of uncertainty shares a unique association with worry that is not accounted for by these other cognitive factors. Overall, the findings provide evidence of construct validity and underscore the role of intolerance of uncertainty in the conceptualization of worry.

Adaptation, Psychological↗

PubMed2006

A comparison of intolerance of uncertainty in analogue obsessive-compulsive disorder and generalized anxiety disorder.

Intolerance of uncertainty has been defined as the unwillingness to tolerate the possibility that negative events may occur in the future, no matter how low the probability [Personality Individual Differences 17 (1994), 791-802]. Previous research suggests that intolerance of uncertainty may be more specific to worry and generalized anxiety disorder (GAD) than to other anxiety disorders [e.g., Dugas, M. J., Buhr, K., & Ladouceur, R. (2004). The role of intolerance of uncertainty in the etiology and maintenance of generalized anxiety disorder. In R. G. Heimberg, C. L. Turk, & D. S. Mennin (Eds.), Generalized anxiety disorder: Advances in research and practice (pp. 143-163). New York: Guilford Press]. However, Tolin et al. [J. Anxiety Disorders 17 (2003), 233-242] argued that intolerance of uncertainty may also play a central role in obsessive-compulsive disorder (OCD). Therefore, the current study compared intolerance of uncertainty in individuals with analogue GAD and/or OCD. Intolerance of uncertainty was strongly related to pathological worry, GAD symptoms, and OCD symptoms; however, neither worry nor GAD was found to be more strongly associated with intolerance of uncertainty than OCD. Further, individuals with analogue GAD or OCD reported more intolerance of uncertainty than controls, but they did not differ significantly from each other. These findings suggest that intolerance of uncertainty may be a central theme in a number of the anxiety disorders.

Adaptation, Psychological↗

PubMed2006

Uncertainty evaluation in the chloroquine phosphate potentiometric titration: application of three different approaches.

A measurement result cannot be properly interpreted if not accompanied by its uncertainty. Several methods to estimate uncertainty have been developed. From those methods three in particular were chosen in this work to estimate the uncertainty of the Eu. Ph. chloroquine phosphate assay, a potentiometric titration commonly used in medicinal control laboratories. The famous error-budget approach (also called bottom-up or step-by-step) described by the ISO Guide to the expression of Uncertainty in Measurement (GUM) was the first method chosen. It is based on the combination of uncertainty contributions that have to be directly derived from the measurement process. The second method employed was the Analytical Method Committee top-down which estimates uncertainty through reproducibility obtained during inter-laboratory studies. Data for its application were collected in a proficiency testing study carried out by over 50 laboratories throughout Europe. The last method chosen was the one proposed by Barwick and Ellison. It uses a combination of precision, trueness and ruggedness data to estimate uncertainty. These data were collected from a validation process specifically designed for uncertainty estimation. All the three approaches presented a distinctive set of advantages and drawbacks in their implementation. An expanded uncertainty of about 1% was assessed for the assay investigated.

Chloroquine↗

PubMed2003

Uncertainty in toxicological risk assessment for non-carcinogenic health effects.

Uncertainty in risk assessment results from the lack of knowledge on toxicity to the target population for a substance. Currently used deterministic risk assessment methods yield human limit values or margins of safety (MOS) without quantitative measurements of uncertainty. Qualitative and quantitative uncertainty analysis would enable risk managers to better judge the consequences of different management options. This article discusses sources of uncertainty and possibilities for quantification of uncertainty associated with different steps in the risk assessment of non-carcinogenic health effects. Knowledge gaps causing uncertainty in risk assessment are overcome by extrapolation. Distribution functions for extrapolation factors are based on empirical data and provide information about the extent of uncertainty introduced by these factors. Whereas deterministic methods can account only qualitatively for uncertainty of the resulting human limit value, probabilistic risk assessment methods are able to quantify several aspects of uncertainty. However, there is only limited experience with these methods in practice. Their acceptance and future application will depend on the establishment of evidence based distribution functions, flexibility and practicability of the methods, and the unambiguity of the results.

Animals↗

PubMed2003

Risk analysis under uncertainty, the precautionary principle, and the new EU chemicals strategy.

Three categories of uncertainty in relation to risk assessment are defined; uncertainty in effect, uncertainty in cause, and uncertainty in the relationship between a hypothesised cause and effect. The Precautionary Principle (PP) relates to the third type of uncertainty. Three broad descriptions of the PP are set out, uncertainty justifies action, uncertainty requires action, and uncertainty requires a reversal of the burden of proof for risk assessments. The application of the PP is controversial but what matters in practise is the precautionary action (PA) that follows. The criteria by which the PAs should be judged are detailed. This framework for risk assessment and management under uncertainty is then applied to the envisaged European system for the regulation of chemicals. A new EU regulatory system has been proposed which shifts the burden of proof concerning risk assessments from the regulator to the producer, and embodies the PP in all three of its main regulatory stages. The proposals are critically discussed in relation to three chemicals, namely, atrazine (an endocrine disrupter), cadmium (toxic and possibly carcinogenic), and hydrogen fluoride (a toxic, high-production-volume chemical). Reversing the burden of proof will speed up the regulatory process but the examples demonstrate that applying the PP appropriately, and balancing the countervailing risks and the socio-economic benefits, will continue to be a difficult task for the regulator. The paper concludes with a discussion of the role of precaution in the management of change and of the importance of trust in the effective regulation of uncertain risks.

Chemical Industry↗

PubMed2006

Uncertainty in predictions of disease spread and public health responses to bioterrorism and emerging diseases.

Concerns over bioterrorism and emerging diseases have led to the widespread use of epidemic models for evaluating public health strategies. Partly because epidemic models often capture the dynamics of prior epidemics remarkably well, little attention has been paid to how uncertainty in parameter estimates might affect model predictions. To understand such effects, we used Bayesian statistics to rigorously estimate the uncertainty in the parameters of an epidemic model, focusing on smallpox bioterrorism. We then used a vaccination model to translate the uncertainty in the model parameters into uncertainty in which of two vaccination strategies would provide a better response to bioterrorism, mass vaccination, or vaccination of social contacts, so-called "trace vaccination." Our results show that the uncertainty in the model parameters is remarkably high and that this uncertainty has important implications for vaccination strategies. For example, under one plausible scenario, the most likely outcome is that mass vaccination would save approximately 100,000 more lives than trace vaccination. Because of the high uncertainty in the parameters, however, there is also a substantial probability that mass vaccination would save 200,000 or more lives than trace vaccination. In addition to providing the best response to the most likely outcome, mass vaccination thus has the advantage of preventing outcomes that are only slightly less likely but that are substantially more horrific. Rigorous estimates of uncertainty thus can reveal hidden advantages of public health strategies, suggesting that formal uncertainty estimation should play a key role in planning for epidemics.

Bayes Theorem↗

PubMed2006

A probabilistic arsenic exposure assessment for children who contact chromated copper arsenate (CCA)-treated playsets and decks, Part 2: Sensitivity and uncertainty analyses.

A probabilistic model (SHEDS-Wood) was developed to examine children's exposure and dose to chromated copper arsenate (CCA)-treated wood, as described in Part 1 of this two-part article. This Part 2 article discusses sensitivity and uncertainty analyses conducted to assess the key model inputs and areas of needed research for children's exposure to CCA-treated playsets and decks. The following types of analyses were conducted: (1) sensitivity analyses using a percentile scaling approach and multiple stepwise regression; and (2) uncertainty analyses using the bootstrap and two-stage Monte Carlo techniques. The five most important variables, based on both sensitivity and uncertainty analyses, were: wood surface residue-to-skin transfer efficiency; wood surface residue levels; fraction of hand surface area mouthed per mouthing event; average fraction of nonresidential outdoor time a child plays on/around CCA-treated public playsets; and frequency of hand washing. In general, there was a factor of 8 for the 5th and 95th percentiles and a factor of 4 for the 50th percentile in the uncertainty of predicted population dose estimates due to parameter uncertainty. Data were available for most of the key model inputs identified with sensitivity and uncertainty analyses; however, there were few or no data for some key inputs. To evaluate and improve the accuracy of model results, future measurement studies should obtain longitudinal time-activity diary information on children, spatial and temporal measurements of residue and soil concentrations on or near CCA-treated playsets and decks, and key exposure factors. Future studies should also address other sources of uncertainty in addition to parameter uncertainty, such as scenario and model uncertainty.

Arsenates↗

PubMed2007

Perceptions of veterinarians and clients to expressions of clinical uncertainty.

OBJECTIVES: The aim of this study was to explore the attitudes of veterinarians and clients towards expressions of clinical uncertainty. METHODS: Questionnaires that assessed the respondent's attitudes towards expressions of clinical uncertainty were completed by clients at six small animal practices. In addition, questionnaires that evaluated what veterinarians thought their client's attitudes would be towards expressions of clinical uncertainty were completed by veterinarians. The responses from clients and veterinarians were statistically compared. RESULTS: Veterinarians significantly underestimated the desire of clients to be told about uncertainties in treatment and significantly overestimated how the expression of uncertainty would generally reduce client confidence. Veterinarians significantly overestimated the loss of client confidence resulting from saying "I am not sure about this" and from asking a nurse for advice. Both clients and veterinarians considered that verbal expressions of uncertainty would lead to a greater reduction in client confidence than behavioural expressions of uncertainty. CLINICAL SIGNIFICANCE: This study suggests that most clients want to be told about their veterinarian's clinical uncertainties, and how this uncertainty is expressed can markedly influence client confidence.

Attitude of Health Personnel↗

PubMed2004

Social support and the management of uncertainty for people living with HIV or AIDS.

People with chronic and acute illnesses experience uncertainty about their prognoses, potential treatments, social relationships, and identity concerns. In a focus group study of people living with HIV or AIDS, we examined how social support may facilitate or interfere with the management of uncertainty about health, identity, and relationships. We found that support from others helps people with HIV or AIDS to manage uncertainty by (a) assisting with information seeking and avoiding, (b) providing instrumental support, (c) facilitating skill development, (d) giving acceptance or validation, (e) allowing ventilation, and (f) encouraging perspective shifts. Respondents also reported a variety of ways in which supportive others interfered with uncertainty management or in which seeking support imposed costs. Problems associated with social support and uncertainty management included a lack of coordination in uncertainty management assistance, the addition of relational uncertainty to illness uncertainty, and the burden of others' uncertainty management. Our study reveals strategies respondents used to manage costs and complications of receiving support, including developing an active or self-advocating orientation, reframing supportive interactions, withdrawing from nonproductive social situations, selectively allowing others to be support persons, and maintaining boundaries.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Evaluation of uncertainty of measurement in routine clinical chemistry--applications to determination of the substance concentration of calcium and glucose in serum.

We studied the uncertainty of measurement for the calcium and glucose (amount of) substance concentrations in serum. The evaluation follows a four-step procedure, which complies with the ISO document Guide to the Expression of Uncertainty in Measurement (GUM). The applications were chosen to represent commonly used measuring systems in medical laboratories. The uncertainty components are quantified using observations of the measuring system, and information from calibration certificates, instrument specifications and literature. The evaluation focuses on the measurement step but empirical terms are used to illustrate how the pre-analytical phase and patient-related issues can be accounted for. The software GUM Workbench was used to facilitate calculations and to visualize the importance of each uncertainty component. The combined standard uncertainties (u(c)) for the measurands were < or =2% including the pre-analytical uncertainty sources. The patient-related source is discussed in relation to clinician's diagnosis and decision-making. The evaluation, as carried out here for calcium and glucose substance concentration measurements, can easily be applied to many other measurands in clinical chemistry. This work emphasizes that the internal quality control can provide much of the information needed in the uncertainty evaluation, and that external quality assessment (EQA) schemes are important in the control of the uncertainty evaluated by the individual laboratories. Due to statistical and metrological limitations routine EQA schemes should themselves not be used as a means of uncertainty evaluation.

Bias↗

PubMed2005

Sources of uncertainty in economic analysis of the Water Framework Directive.

The Water Framework Directive (WFD) imposes a new approach to water resource management in the EU states. Uncertainty surrounding its implementation, however, could badly affect the achievement of the objectives set by the Directive. Although not directly linked to a set of techniques to deal with it, the WFD and accompanying guidance documents mention uncertainty as a relevant factor in implementing the WFD and especially in the context of economic analysis of water uses. In this paper we review several sources of uncertainty surrounding economic analysis focusing on uncertainty related to socioeconomic descriptors of river basins and water uses and uncertainty surrounding the selection of measures (WFD article 11). While a number of sources of uncertainty in socioeconomic descriptors of river basins and water uses are discussed, we argue that the transformation of this information into hydrological spatial units may turn out to be a real challenge for uncertainty assessment. For the choice of the most appropriate measures, we distinguish between uncertainty being 'internalised' in decisions (by using stochastic decision methods) and uncertainty stemming from the application of these methods.

Conservation of Natural Resources↗

PubMed2004

Production of certified reference materials for mycotoxins: IRMM's view on the assessment of uncertainties.

Analytical difficulty and the economic importance of controlling mycotoxin levels in food and feed led the Community Bureau of Reference (BCR) to prepare a series of certified reference materials (CRM) for various mycotoxins. Because of the wide acceptance of these CRM and the need to ensure the comparability and traceability of measurements in the future it is necessary to prepare and certify new batches of mycotoxin reference materials (RM). In the following text two different approaches for evaluation of the characterisation uncertainty of CRM will be compared using the certification of aflatoxin M(1) (AfM(1)) in milk powder as an example. The conventional approach is based on evaluation of characterisation exercise data; the alternative approach is based on measurement uncertainties of the employed analytical methods. Because laboratories are using totally different approaches to estimate the measurement uncertainties, combination of the uncertainties obtained from the participating laboratories was not recommended. Therefore, a new integrated approach for assessment of the measurement uncertainties of the analytical methods on the basis of additional data collected during the characterisation exercise will be described. The conventional approach was found to be the most appropriate and economical approach to evaluate the characterisation uncertainty as a characterisation exercise must be performed anyway to establish the property values of candidate (C)RM, irrespective of whether or not reliable measurement uncertainties can be provided by the laboratories. An integrated approach for assessment of measurement uncertainties based on additional characterisation data as applied here to enable use of an uncertainty-based approach provides more information but is too time-consuming and cost-intensive to become common practice.

Aflatoxin M1↗

PubMed2004

Estimation of uncertainty in pKa values determined by potentiometric titration.

A procedure is presented for estimation of uncertainty in measurement of the pK(a) of a weak acid by potentiometric titration. The procedure is based on the ISO GUM. The core of the procedure is a mathematical model that involves 40 input parameters. A novel approach is used for taking into account the purity of the acid, the impurities are not treated as inert compounds only, their possible acidic dissociation is also taken into account. Application to an example of practical pK(a) determination is presented. Altogether 67 different sources of uncertainty are identified and quantified within the example. The relative importance of different uncertainty sources is discussed. The most important source of uncertainty (with the experimental set-up of the example) is the uncertainty of pH measurement followed by the accuracy of the burette and the uncertainty of weighing. The procedure gives uncertainty separately for each point of the titration curve. The uncertainty depends on the amount of titrant added, being lowest in the central part of the titration curve. The possibilities of reducing the uncertainty and interpreting the drift of the pK(a) values obtained from the same curve are discussed.

Acids↗

PubMed1993

Physician uncertainty and the art of persuasion.

Incomplete information is a chronic feature of medica markets. Much attention has focused on information asymmetries between physicians and their patients. In contrast, physician uncertainty has received far less attention. This is a significant omission. Physician uncertainty may be an even more important reason than consumer uncertainty for the high cost of health care. This paper reviews and evaluates major approaches for managing physician uncertainty. We argue that quantitative approaches alone, such as scientific advancement and the application of decision analysis to clinical reasoning, are insufficient for dealing with uncertainty. Qualitative approaches, such as forging consensus through expert panels, and teaching physicians to accept and cope with uncertainty, will play a valuable role in promoting more effective clinical decision-making under conditions of uncertainty. The current tensions between those who would eradicate physician uncertainty through quantitative approaches and those who favor qualitative methods has parallels in many other fields, including economics and mathematics. These tensions are unfortunate, since the most promising initiative to promote better clinical decision-making will likely need to draw upon both approaches. The recent initiative to implement medical practice guidelines is one example of a broad-based approach to improve clinical decision-making. Guidelines draw upon available scientific evidence, but typically involve consensus-building as well. They seek to persuade and educate physicians about appropriate treatments, without mandating changes in physician treatment patterns. Given the persistent uncertainties physicians will undoubtedly confront regarding appropriate clinical decision-making, this flexible approach may be the best way to mitigate market failures resulting from inappropriate clinical decisions.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Competence↗

PubMed1991

The role of uncertainty analysis in treatment planning.

The role of uncertainty analysis in 3-D treatment planning systems was addressed by four institutions which contracted with NCI to evaluate high energy photon external beam treatment planning. Treatment plans were developed at eight disease sites and the effects of uncertainties assessed in a number of experiments. Uncertainties which are patient-site specific included variations in the delineation of target volumes and normal tissues and the effects of positional uncertainties due to physiological motion and setup nonreproducibility. These were found to have a potentially major impact on the doses to the target volumes and to critical normal tissues which could result in significantly altered probabilities of tumor control and normal tissue complications. Other uncertainties, such as the conversion of CT data to electron densities, heterogeneities and dose calculation algorithms' weaknesses, are related to physical processes. The latter was noted to have the greatest potential contribution to uncertainty in some sites. A third category of uncertainty related to the treatment machine, the consequences of compensator misregistration, are exclusive to the site and the treatment portal. Because conventional treatment planning systems have not incorporated uncertainty analysis, tools and techniques had to be devised for this work; further development in this area is needed. Many of the analyses could not have been done without full 3-D capabilities of the planning systems, and it can be anticipated that the availability of uncertainty analysis in these systems which allow nontraditional beam arrangements will be of great value.

Humans↗

PubMed2003

Sources of uncertainty in pesticide fate modelling.

There is worldwide interest in the application of probabilistic approaches to pesticide fate models to account for uncertainty in exposure assessments. The first steps in conducting a probabilistic analysis of any system are: (i) to identify where the uncertainties come from; and (ii) to pinpoint those uncertainties that are likely to affect most of the predictions made. This article aims at addressing those two points within the context of exposure assessment for pesticides through a review of the different sources of uncertainty in pesticide fate modelling. The extensive listing of sources of uncertainty clearly demonstrates that pesticide fate modelling is laced with uncertainty. More importantly, the review suggests that the probabilistic approaches, which are typically being deployed to account for uncertainty in the pesticide fate modelling, such as Monte Carlo modelling, ignore a number of key sources of uncertainty, which are likely to have a significant effect on the prediction of environmental concentrations for pesticides (e.g. model error, modeller subjectivity). Future research should concentrate on quantifying the impact these uncertainties have on exposure assessments and on developing procedures that enable their integration within probabilistic assessments.

Animals↗