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Support from health care providers and parental uncertainty during the diagnosis phase of perinatally acquired HIV infection.

Support from health care providers (HCPs) can reduce parental uncertainty during the diagnosis of serious childhood conditions, but the effect may change when the parent is chronically ill. The purpose of this study was to learn whether a mother's uncertainty about her HIV diminished the effect of support from HCPs on parental uncertainty during the diagnosis of perinatally acquired HIV infection. Participants were 25 women who accompanied their biological children to pediatric HIV screening clinics at two urban sites. Questionnaires were read to participants in a private area of clinic. To test for mediation, three models for parental uncertainty were examined using regression procedures. The results suggest that when a mother has HIV infection, HCPs can maximize the effect of their support on parental uncertainty by also addressing mother's uncertainty about her HIV during the baby's screening visits.

AIDS Serodiagnosis↗

PubMed2001

Chronic and temporarily activated causal uncertainty beliefs and stereotype usage.

In 3 studies, we examined the hypothesis that the effects of stereotype usage on target judgments are moderated by causal uncertainty beliefs and related accuracy goal structures. In Study 1, we focused on the role of chronically accessible causal uncertainty beliefs as predictors of a target's level of guilt for an alleged academic misconduct offense. In Study 2, we examined the role of chronic causal uncertainty reduction goals and a manipulated accuracy goal; in Study 3, we investigated the role of primed causal uncertainty beliefs on guilt judgments. In all 3 studies, we found that activation of causal uncertainty beliefs and accuracy concerns was related to a reduced usage of stereotypes. Moreover, this reduction was not associated with participants' levels of perceived control, depression, state affect, need for cognition, or personal need for structure. Results are discussed in terms of their implications for the model of causal uncertainty and, more generally, in terms of the motivational processes underlying stereotype usage.

Adult↗

PubMed2000

Estimation of precision and efficiency mass transfer steps for the determination of pesticides in vegetables aiming at the expression of results with reliable uncertainty.

A 'bottom-up' approach for the expression of results obtained from analytical methods that include analytical steps with recovery inherently different from 100% [mass transfer steps (MTS): extraction, evaporation, clean-up procedures, digestion, etc.] is presented. The estimation of the combination of all MTS uncertainty involves the comparison of the experimental dispersion of replicated analyses of spiked samples with the estimation of the uncertainty obtained for the combination of all uncertainty sources except MTS ones ('incomplete' estimation). The estimation of MTS uncertainty by difference is performed after evaluating the statistical difference between the 'incomplete' estimation and the experimental dispersion (F-test). When the two estimations are statistically equivalent, the MTS uncertainty is considered to be negligible in relation to the other sources budget. The assumption of constancy of MTS performance within the analytical range is tested through single analyses at several concentration levels and is evaluated by the inclusion of the expected values at the intervals resulting from the combination of the MTS uncertainty estimation performed at one concentration level and the 'incomplete' estimation. The developed methodology can also be useful for method optimisation and validation and for the detection of small trends in results. The determination of pesticides in sweet peppers by GC-NPD was used to explore the above concepts.

Chromatography, Gas↗

PubMed2001

Optimised uncertainty at minimum overall cost to achieve fitness-for-purpose in food analysis.

An optimised uncertainty (OU) methodology is described, that balances the uncertainty of measurements on food against the cost of the measurements and the other expenditure that may arise as a consequence of the possible misclassification of the food. Measurement uncertainty from the sources of primary sampling and chemical analysis is estimated using an existing technique, which is based on the taking of duplicated samples and duplicated analyses. The input information required for the OU method is the actual costs of sampling and analysis, and the expected costs that could arise from either the 'false positive' or 'false negative' classification of batches of food. A loss function is then constructed that calculates the 'expectation of loss' which will arise for a given uncertainty of measurement. This function has a minimum value of cost at an optimal value of uncertainty, which can be estimated numerically. Application of this OU method to a case study on the determination of aflatoxin levels in pistachio nuts has demonstrated this minimum value. Below the optimum value of uncertainty, the costs increased due to higher measurement costs. Above the optimum value, the costs increased due to increasing probability of expenditure on consequences such as unnecessary rejection of the batch, potential litigation or loss of corporate reputation because of undetected contamination. A second stage of the OU method optimises the division of the expenditure on the measurement between that on sampling and that on analysis. The technique is demonstrated as a useful new approach for judging the fitness-for-purpose of chemical measurements in the food industry. Several areas for further development of the technique are identified. By matching the expenditure on the measurement against that caused by the misclassification of the food, the OU method has the potential to reduce overall expenditure whilst ensuring an appropriate reliability of measurement.

Aflatoxins↗

PubMed2002

From experimental design to uncertainty estimation for the European Pharmacopoeia HPLC analysis of human insulin.

In this paper the process from experimental design (e.g. ruggedness test) to uncertainty estimation is described. The uncertainty estimate was calculated for the peak area of insulin plus A21 desamido insulin resulting from an HPLC analysis of a sample of an injectable human insulin preparation, Actrapid HM 100 IU ml(-1) (Novo Nordisk A/S). The analytical method used was the European Pharmacopoeia assay. (4) An expanded uncertainty (1) of 1.8% (of the area from the HPLC analysis) at an approximately 95% confidence level was found and confirmed by a validation study. This uncertainty refers to the peak area of the analyte from a single injection of the sample. The input parameters to the uncertainty estimate were found from a factorial experimental design (e.g. ruggedness test) consisting of 9 factors applied to the HPLC analysis. The input parameters were chosen to cover the probable contributors to the variability of the measured area of the HPLC analysis, including the sample preparation, but excluding uncertainty deriving from the reference material(s).

Chromatography, High Pressure Liquid↗

PubMed1996

Quantification of the uncertainties in resultant joint moments computed in a dynamic activity.

Resultant joint moments are an important variable with which to examine human movement, but the uncertainty with which resultant joint moments are calculated is often ignored. This paper presents a procedure for examining the uncertainty with which resultant joint moments are calculated. The uncertainty was calculated by changing the parameters and variables required to compute the resultant joint moments, by amounts relating to their estimated uncertainties, and then quantifying the resulting change in the resultant joint moments. The procedure was applied to the elbow joint during loaded elbow flexion executed at maximum volitional speed. For this activity, the estimated moments were most sensitive to uncertainties in the derivatives of the position data. A number of other sources of error and uncertainty were identified which warrant further investigation. The protocols outlined in this study are applicable to other activities.

Biomechanical Phenomena↗

PubMed2002

Intake estimation of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in salmon: the inclusion of uncertainty.

Dioxins and dioxin-like PCBs are given toxic equivalency factors (TEFs) in order to calculate the combined toxic equivalence (TEQ) of these contaminants in a sample of food. This study calculates the probability of an average consumer exceeding the recommended tolerable daily intake of 1-4 pg WHO-TEQ kg(-1) bw day(-1) as the amount of salmon in the diet is increased. Probabilistic risk analysis is used to account for the known uncertainties in this calculation. When the TEF uncertainty was excluded with no salmon consumption, the background dietary intake ranged from 1.36 to 1.78 pg TEQ kg(-1) bw day(-1). A weekly consumption of three standard salmon portions resulted in a 36% chance of exceeding the upper limit of the TDI. Inclusion of the TEF uncertainty increased the background dietary intake range from 2.1 to 4.4 pg TEQ kg(-1) bw day(-1), and the weekly consumption of one salmon portion resulted in a 79% chance of the average consumer exceeding the upper TDI. The most important factors contributing to the uncertainty in these results were, in order of magnitude, the TEF for PCB 126 and the sampling uncertainty (sample size) followed by the measurement uncertainty of PCB 126. We recommend that it is more important to increase sample size and produce more precise estimates in the TEF than to improve analytical accuracy.

Animals↗

PubMed2003

Methods for quantifying variability and uncertainty in AP-42 emission factors: case studies for natural gas-fueled engines.

Quantitative methods for characterizing variability and uncertainty were applied to case studies of oxides of nitrogen and total organic carbon emission factors for lean-burn natural gas-fueled internal combustion engines. Parametric probability distributions were fit to represent inter-engine variability in specific emission factors. Bootstrap simulation was used to quantify uncertainty in the fitted cumulative distribution function and in the mean emission factor. Some methodological challenges were encountered in analyzing the data. For example, in one instance, five data points were available, with each data point representing a different market share. Therefore, an approach was developed in which parametric distributions were fitted to population-weighted data. The uncertainty in mean emission factors ranges from as little as approximately +/-10% to as much as -90 to +180%. The wide range of uncertainty in some emission factors emphasizes the importance of recognizing and accounting for uncertainty in emissions estimates. The skewness in some uncertainty estimates illustrates the importance of using numerical simulation approaches that do not impose restrictive symmetry assumptions on the confidence interval for the mean. In this paper, the quantitative method, the analysis results, and key findings are presented.

Air Pollutants↗

PubMed1999

Uncertainty analysis in polymer gel dosimetry.

Verification of advanced radiotherapy treatment modalities requires measurement of three-dimensional absorbed dose distributions with high spatial resolution and precision. Polymer gel dosimeters combined with magnetic resonance imaging may be able to fulfil this requirement. However, verification requires that the uncertainty in the dosimeter is well known. One method of estimating the overall uncertainty in polymer gel dosimeters involves the propagation of the uncertainty in the R2 (nuclear magnetic resonance relaxation rate) map and the uncertainties in the calibration data. This work shows that using this method with current data suggests that the lowest uncertainty currently obtainable is about 3% at 8 Gy and 7% at 2 Gy. Furthermore, the most significant reductions in overall uncertainty will be achieved by reducing the noise in the R2 map.

Acrylic Resins↗

PubMed2004

Study of the uncertainty in estimation of the exposure of non-human biota to ionising radiation.

Uncertainty in estimations of the exposure of non-human biota to ionising radiation may arise from a number of sources including values of the model parameters, empirical data, measurement errors and biases in the sampling. The significance of the overall uncertainty of an exposure assessment will depend on how the estimated dose compares with reference doses used for risk characterisation. In this paper, we present the results of a study of the uncertainty in estimation of the exposure of non-human biota using some of the models and parameters recommended in the FASSET methodology. The study was carried out for semi-natural terrestrial, agricultural and marine ecosystems, and for four radionuclides (137Cs, 239Pu, 129I and 237Np). The parameters of the radionuclide transfer models showed the highest sensitivity and contributed the most to the uncertainty in the predictions of doses to biota. The most important ones were related to the bioavailability and mobility of radionuclides in the environment, for example soil-to-plant transfer factors, the bioaccumulation factors for marine biota and the gut uptake fraction for terrestrial mammals. In contrast, the dose conversion coefficients showed low sensitivity and contributed little to the overall uncertainty. Radiobiological effectiveness contributed to the overall uncertainty of the dose estimations for alpha emitters although to a lesser degree than a number of transfer model parameters.

Agriculture↗

PubMed1999

Women's uncertainties, coping, and moods regarding abnormal papanicolaou results.

The overall purpose of this study was to understand the process of coping with the news of abnormal cervical cancer screening results. The specific aims were (1) to compare women's uncertainty about the implications of abnormal Papanicolaou (Pap) tests and women's psychological distress over time and (2) to describe relationships among uncertainty, perceived coping ability, coping strategies that were used and helpful, and psychological distress. Seventy-five women were interviewed using standardized measures after hearing the news of their abnormal Paps tests; 40 completed similar questionnaires before follow-up colposcopy, and 35 of these also completed questionnaires after colposcopy. Women's uncertainty about abnormal Pap test results decreased over time. Negative mood scores, reflecting psychological distress, did not change over time. Uncertainty about Pap tests, ambiguity about cancer, and perceived inability to deal with Pap test results were related positively. Uncertainty was related positively to the coping strategy of catharsis as well as to negative mood scores both after receiving the news and precolposcopy. Catharsis was associated with higher negative mood scores, but acceptance was associated with lower negative mood scores. The helpfulness of relaxation and diversion was associated with lower negative mood scores. Clinical interventions can address women's uncertainty and promote coping strategies to reduce psychological distress among women with abnormal cervical cancer screening results.

Adaptation, Psychological↗

PubMed2002

Uncertainty analysis of the weighted equivalent lung dose per unit exposure to radon progeny in the home.

A parameter uncertainty analysis has been performed to derive the probability distribution of the weighted equivalent dose to lung for an adult (w(lung) H(lung)) per unit exposure to radon progeny in the home. The analysis was performed using the ICRP Publication 66 human respiratory tract model (HRTM) with tissue weighting factor for the lung, w(lung) = 0.12 and the radiation weighting factor for alpha particles, wR = 20. It is assumed that the HRTM is a realistic representation of the physical and biological processes, and that the parameter values are uncertain. The parameter probability distributions used in the analysis were based on a combination of experimental results and expert judgement from several prominent European scientists. The assignment of the probability distributions describing the uncertainty in the values of the assigned fractions (ABB, Abb, AAI) of the tissue weighting factor proved difficult in practice due to lack of quantitative data. Because of this several distributions were considered. The results of the analysis give a mean value of w(lung) H(lung) per unit exposure to radon progeny in the home of 15 mSv per working level month (WLM) for a population. For a given radon gas concentration, the mean value of w(lung) H(lung) per unit exposure is 13 mSv per 200 Bq.m(-3).y of 222Rn. Parameters characterising the distributions of w(lung) H(lung) per unit exposure are given. If the ICRP weighting factors are fixed at their default values (ABB, Abb, AAI = 0.333, 0.333, 0.333; w(lung) = 0.12; and wr = 20) then on the basis of this uncertainty analysis it is extremely unlikely (P approximately 0.0007) that a value of Hw/Pp for exposure in the home is as low as 4 mSv per WLM, the value determined with the epidemiological approach. Even when the uncertainties in the ABB, Abb, AAI, values are included then this probability is predicted to be between 0.01 to 0.08 depending upon the distribution assumed for describing the uncertainties in the ABB, Abb, AAI, values. Thus, it is concluded that the uncertainties in the HRTM parameters considered in this study cannot totally account for the discrepancy between the dosimetric and epidemiological approaches.

Administration, Inhalation↗

PubMed2006

Uncertainty in radiation dosimetry: basic concepts and methods.

Principally, uncertainty is associated with measured and computed values. The basic concepts of uncertainty are outlined, an overview on methods for its determination is given and the application of uncertainties in quality assurance is discussed. Based on the Guide to the expression of uncertainty in measurement and a forthcoming supplement to it, the paper identifies modelling of measurement or computation and the use of a probability distribution functions (PDFs) for expressing the degree of belief in possible values as basic concepts. All presently used proper methods for determining uncertainty can be derived from the Markov formula. Optimisation of measurements and computations as well as the acceptance of results by others are identified as the two major tasks of quality assurance based on analysing and stating uncertainty.

Bayes Theorem↗

PubMed1994

Propagation of variance uncertainty calculation for an autopsy tissue analysis.

An assay value is almost useless unless it is accompanied by a measure of the uncertainty associated with that value. The uncertainty value should reflect all the major sources of variation and bias affecting the assay and should provide a specified level of confidence (for example, 95%). An approach to uncertainty calculation that includes the uncertainty due to instrument calibration, values of the standards, and intermediate measurements as well as counting statistics is presented and applied to the analysis of an autopsy tissue. This approach, usually called propagation of variance, attempts to clearly distinguish between errors that have systematic (bias) effects and those that have random effects on the assays. The effects of these different types of errors are then propagated to the assay using formal statistical techniques. The result is an uncertainty on the assay that has a defensible level of confidence and which can be traced to individual major contributors. However, since only measurement steps are readily quantified and since all models are approximations, it is emphasized that without empirical verification, a propagation of uncertainty model may be just a fancy model with no connection to reality.

Autopsy↗

PubMed1996

Uncertainty of historical measurements of 131I in Hanford-area vegetation.

The Hanford Environmental Dose Reconstruction (HEDR) Project was conducted to estimate the radiation dose that individuals could have received as a result of emissions to the air and water from Hanford Site operations since 1944. The largest doses were to the human thyroid gland from 131I released into the atmosphere from Hanford facilities in the 1945-1947 time period. In support of the dose reconstruction effort, a database of historical environmental radioactivity measurements was constructed. This database includes measurements of total radioactivity for vegetation samples collected from 1945-1948 and counted using a Geiger-Mueller (GM) detector system. Because the factors used at that time to convert the GM counts to 131I activity did not take all parameters into account, and because some parameter values were inaccurate, more accurate conversion factors were developed as part of the HEDR Project. These factors can be used to estimate the actual historical activity levels. This paper summarizes the Monte Carlo uncertainty and sensitivity analysis methods used to assess the uncertainty of the newly reconstructed historical vegetation 131I activities and to identify the parameters that contributed the most uncertainty to these reconstructed activities. Based on the study of two vegetation (sagebrush) samples collected in the mid-1940's, it appears that the true 131I activity of the historical vegetation samples should be within a factor of three of the reconstructed activity. Also, the uncertainty in the parameter Icf (the fraction of the background-corrected GM measurement of a vegetation sample that resulted from 131I) was found to contribute the most uncertainty to the reconstructed 131I activities when the uncertainty in Icf was large.

Air Pollutants, Radioactive↗

PubMed1996

Struggling to gain meaning: living with the uncertainty of breast cancer.

Uncertainty is a common experience for women living with breast cancer, particularly when treatment cannot assure disease cure. The study described in this article sought to provide insight into uncertainty experiences for women living with breast cancer. Hermeneutic phenomenology and photographic hermeneutics were used to describe and interpret uncertainty for nine women between 2 and 6 years posttreatment for breast cancer. Data were collected using interviews and interpretations of photographs. Five themes of uncertainty among women were uncovered. Major study findings included support for a reconceptualization of Mishel's Uncertainty in Illness Theory and the explication of growth-producing aspects of uncertainty.

Adaptation, Psychological↗

PubMed1993

Congruence in uncertainty between individuals with multiple sclerosis and their spouses.

The purpose of this study was to examine differences in the perception of illness uncertainty between husband and wife and to explore how these differences influence emotional well-being. Mood and family satisfaction were used as indicators of emotional well-being. The sample consisted of sixty-one married couples in which one spouse had multiple sclerosis. Results supported that both individual perceptions of illness uncertainty and congruence in perceived uncertainty between spouses may have negative effects on marital partners. For both spouses, those who reported higher levels of uncertainty were more likely to have lower moods and feel more dissatisfied with family life. However, the most crucial factor in determining family satisfaction for spouses with multiple sclerosis was their own perception of illness uncertainty, while for well spouses, it was the congruence between each partner's perception of the illness uncertainty.

Activities of Daily Living↗

PubMed1992

Assessing the effect of uncertainty in intracavitary electrode position on endocardial potential estimates.

The aim of this simulation study is to determine the effect of uncertainty in intracavitary probe electrode position on the accuracy of estimated endocardial potentials. Intracavitary probe position uncertainty is simulated by randomly moving an idealized probe surface about the center of an idealized left ventricular endocardial surface. These random deviations represent possible probe locations that are incorporated as correlated noise. An optimum inverse transfer coefficient matrix, relating intracavitary potentials to endocardial potentials, is computed and subsequently used to calculate the best linear estimate of the true endocardial potentials. For uncorrelated endocardial potentials and probe position uncertainty within 1.5 mm of the coordinates of the exact probe electrode locations, a root-mean-square (rms) error of 34.0% is obtained. Increasing probe position uncertainties to 3.0 and 6.0 mm results in rms errors of 60.8 and 88.3%, respectively. For endocardial potentials that are 90% dipolar, the rms errors for probe position uncertainties of 1.5, 3.0, and 6.0 mm are 11.3, 19.6, and 28.5%, respectively. These simulation results imply that position uncertainty of a multielectrode, intracavitary probe can be a major source of error in estimating endocardial potentials from intracavitary potentials.

Action Potentials↗