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PubMedDate not supplied

On uncertainty in medical testing.

There is confusion in the medical decision-making literature about how to handle uncertainty in medical tests. In this article, the authors consider the situation in which there is uncertainty about the pretest probability of a disease in a patient as well as uncertainty about the sensitivity and specificity of a diagnostic test for that disease. They discuss how to calculate posttest probabilities of a disease under such uncertainty and how to calculate a distribution for a posttest probability. They show that given certain independence assumptions, uncertainty about these parameters need not complicate the calculation of patient positive predictive values: One can simply use the expected values of the parameters in the standard Bayesian formula for posttest probabilities. The discussion on how to calculate distributions for positive predictive values corrects a common and potentially important error.

Confidence Intervals↗

PubMedDate not supplied

Impact of model, methodological, and parameter uncertainty in the economic analysis of vaccination programs.

Guidelines for economic evaluations insist that the sensitivity of model results to alternative parameter values should be thoroughly explored. However, differences in model construction and analytical choices (such as the choice of a cost-effectiveness or cost-benefit framework) also introduce uncertainty in results, though these are rarely subjected to a thorough sensitivity analysis. In this article, the authors quantify the effect of model, methodological, and parameter uncertainty, taking varicella vaccination as an example. They used 3 different models (a static model, a dynamic model that only looks at the effect of vaccination on varicella, and a dynamic model that also assesses the implications of vaccination for zoster epidemiology) and 2 forms of analysis (cost-benefit and cost-utility). They also varied the discount rate and time frame of analysis. Probabilistic sensitivity analyses were performed to estimate the impact of parameter uncertainty. In their example, model and methodological choice had a profound effect on estimated cost-effectiveness, but parameter uncertainty played a relatively minor role. Under cost-utility analysis, the probabilistic sensitivity analysis suggested that there was a near certainty that vaccination dominates no vaccination, or the other way around, depending on model choice and perspective. Under cost-benefit analysis, vaccination always appeared to be attractive. Thus, the authors clearly show that model and methodological assumptions can have greater impact on results than parameter estimates, although sensitivity analyses are rarely performed on these sources of uncertainty.

Adolescent↗

PubMedDate not supplied

More than just menstrual cramps: symptoms and uncertainty among women with endometriosis.

OBJECTIVE: To examine the frequency, severity, interference with daily life, and symptom distress associated with endometriosis and to explore the relationships among symptoms, emotional distress, uncertainty, and preference for and adequacy of information. DESIGN: A descriptive, cross-sectional correlational study. SETTING: Data were collected at a conference of the Endometriosis Association in Milwaukee, Wisconsin. PARTICIPANTS: A convenience sample of 298 women attending an educational program. MAIN OUTCOME MEASURES: Endometriosis symptoms and symptom distress, emotional distress, and adequacy of information were assessed using author-developed scales. Preference for information was measured by a revision of the Krantz Health Opinion Survey Information Subscale. Uncertainty was assessed using the Mishel Uncertainty in Illness Scale-Community Form. RESULTS: Women experienced multiple symptoms associated with varying levels of distress, including symptoms not typically associated with endometriosis. Participants sought out information but were undecided about whether they had sufficient information about the disease. Uncertainty about endometriosis was relatively high and associated with emotional distress and lack of information about the disease. CONCLUSIONS: Reported symptoms demonstrate the complexity and impact of endometriosis. Women's preference for information and experience of emotional distress and uncertainty suggest the need for information and support. Prospective, controlled studies on the impact of endometriosis and interventions to inform and support patients are needed.

Activities of Daily Living↗

PubMed2004

Triggers of uncertainty about recurrence and long-term treatment side effects in older African American and Caucasian breast cancer survivors.

PURPOSE/OBJECTIVES: To examine the sources of uncertainty in older African American and Caucasian long-term breast cancer survivors by focusing on frequency of triggers of uncertainty about cancer recurrence and physical symptoms linked to long-term treatment side effects. DESIGN: In the context of a larger randomized, controlled treatment-outcome study, data were gathered from 10 monthly follow-up telephone calls by nurses. SETTING: Rural and urban regions of North Carolina. SAMPLE: 244 older women (mean age = 64 years); 73 African American women and 171 Caucasian women who were five to nine years after breast cancer diagnosis. FINDINGS: The most frequent triggers were hearing about someone else's cancer and new aches and pains. The most frequent symptoms were fatigue, joint stiffness, and pain. Although no ethnic differences occurred in the experience of symptoms, Caucasian women were more likely than African American women to report that their fears of recurrence were triggered by hearing about someone else's cancer, environmental triggers, and information or controversy about breast cancer discussed in the media. CONCLUSIONS: Illness uncertainty persisted long after cancer diagnosis and treatment, with most women experiencing multiple triggers of uncertainty about recurrence and a range of symptoms and treatment side effects. IMPLICATIONS FOR NURSING: Nurses can help cancer survivors to identify, monitor, and manage illness uncertainty and emotional distress.

Black or African American↗

PubMed2006

What healthcare students do with what they don't know: the socializing power of 'uncertainty' in the case presentation.

Healthcare students learn to manage clinical uncertainty amid the tensions that emerge between clinical omniscience and the 'truth for now' realities of the knowledge explosion in healthcare. The case presentation provides a portal to viewing the practitioner's ability to manage uncertainty. We examined the communicative features of uncertainty in 31 novice optometry case presentations and considered how these features contributed to the development of professional identity in optometry students. We also reflected on how these features compared with our earlier study of medical students' case presentations. Optometry students, like their counterparts in medicine, displayed a novice rhetoric of uncertainty that focused on personal deficits in knowledge. While optometry and medical students shared aspects of this rhetoric (seeking guidance and deflecting criticism), optometry students displayed instances of owning limits while medical students displayed instances of proving competence. We found that the nature of this novice rhetoric was shaped by professional identity (a tendency to assume an attitude of moral authority or defer to a higher authority) and the clinical setting (inpatient versus outpatient settings). More explicit discussions regarding uncertainty may help the novice unlock the code of contextual forces that cue the savvy member of the community to sanctioned discursive strategies.

Clinical Competence↗

PubMed2002

Illness uncertainty, perceived control, and psychological distress among adolescents with type 1 diabetes.

This study examined the relationship between illness uncertainty, perceived control, and psychological distress among adolescents with type 1 diabetes. Sixty-eight adolescents age 13 to 18 years with type 1 diabetes completed the Children's Uncertainty in Illness Scale, the Perceived Control Scale Media Relations, and the Brief Symptom Inventory. Increased uncertainty was significantly associated with both decreased perceived control and increased psychological distress. Further analyses indicated that the relationship between illness uncertainty and psychological distress was direct and was not mediated or moderated by perceived control. These findings suggest that interventions aimed at managing uncertainty may help decrease psychological distress among adolescents with diabetes.

Adolescent↗

PubMed2004

Incorporation of statistical uncertainty in health economic modelling studies using second-order Monte Carlo simulations.

Health economic modelling studies are of interest to many parties with different responsibilities and diverging interests. Therefore, it is obvious that recognising the relevance of statistical uncertainty and dealing with it appropriately are required to obtain unbiased results from health economic modelling studies, especially when those data are being used for reimbursement decisions. In this manuscript we explore the relevance of the incorporation of statistical uncertainty in a health economic model and identify various types of statistical uncertainty. The concepts were applied to a hypothetical Markov model for a hypothetical antiparkinsonian (AP) product. The method was based on the incorporation of probability distributions in the input variables using a second-order Monte Carlo simulation and the definition of minimum relevant differences for clinical and economic input variables and outcomes. Our paper shows that the outcomes of a health economic model might be severely biased when statistical uncertainty is not taken into account, which justifies the need for the incorporation of statistical uncertainty in a health economic model.

Antiparkinson Agents↗

PubMedDate not supplied

Measurement uncertainty in microbiology.

Testing laboratories wishing to comply with the requirements of ISO/IEC 17025:1999 need to estimate uncertainty of measurement for their quantitative methods. Many microbiological laboratories have had procedures available for monitoring variability in duplicate results generated by laboratory analysts for some time. These procedures, however, do not necessarily include all possible contributions to uncertainty in the calculations. Procedures for estimating microbiological method uncertainty, based on the Poisson distribution, have been published but, at times, the procedures can either underestimate uncertainty or require laboratories to undertake considerable experimental studies and more complex statistical calculations. This paper proposes procedures for estimating uncertainty of measurement in microbiology, whereby routine laboratory quality control data can be analyzed with simple statistical equations. The approaches used in these procedures are also applied to published data and examples, demonstrating that essentially equivalent results can be obtained with these procedures.

Colony Count, Microbial↗

PubMed2005

A qualitative analysis of the experience of uncertainty while awaiting coronary artery bypass surgery.

The aim of this article is to present a qualitative examination of the phenomenon of uncertainty in patients awaiting CABG surgery. Cardiac symptoms are presented as an antecedent to uncertainty and both positive and negative outcomes of uncertainty are discussed. Semi-structured interview questions, based on Mishel's Uncertainty in Illness Theory, were developed to investigate the experience of waiting for CABG surgery and identify what patients were doing: to make their cardiac symptoms more manageable, to relieve their own anxiety while waiting, and to identify why patients felt having CABG surgery would benefit them. Telephone interviews were conducted with a self-selected sample of 25 participants. The qualitative results presented are part of a larger multimethod study examining the psychosomatic experience of waiting for CABG surgery. Data collected from telephone interviews were analyzed using content analysis and constant comparison techniques. Content analysis identified three conceptual categories: i) taking responsibility; ii) getting my life back; and iii) getting it over with. Strategies associated with each of these categories, the consequences of the strategies, and factors that facilitate or constrain their use were also identified. Participants were actively trying to lessen the impact of their cardiac symptoms and were very aware of their own bodies and what actions would exacerbate symptoms or relieve symptoms if they occurred. Participants envisioned physical and psychological improvements for post-CABG surgery. Participants also identified actions they took to limit their anxiety while waiting. Anxiety levels were influenced by family members as well as stories they had heard from friends, family, or acquaintances who had also experienced CABG. This study concluded that the lengthy waits experienced by some patients can create significant psychological disturbance including anxiety and uncertainty about the future. In addition, patient symptom status requires attentive monitoring.

Adaptation, Psychological↗

PubMedDate not supplied

[Uncertainty of measurement as an integral part of the result and a tool of quality of work improvement for the chemical-toxicology laboratory].

An uncertainty in measurements is a numerical defined range that is supposed to find a true value with a given level of probability. The purpose of this study was to estimate a type A and B of uncertainty in the analysis of ethanol using the ADH method and prove it to be useful in lab practice. A large percentage of uncertainty was shown for pipetting of the ADH and perchloric acid solutions. This result formed the basis to make an effort in order to improve the procedure. The results of uncertainty of measurements given by method B are similar to the empiric method A results. The reduction of expenses and time saving of the analysis is an important advantage of the described way of uncertainty.

Alcohol Dehydrogenase↗

PubMed2005

Predicting missing values in a home care database using an adaptive uncertainty rule method.

OBJECTIVES: Contemporary literature illustrates an abundance of adaptive algorithms for mining association rules. However, most literature is unable to deal with the peculiarities, such as missing values and dynamic data creation, that are frequently encountered in fields like medicine. This paper proposes an uncertainty rule method that uses an adaptive threshold for filling missing values in newly added records. A new approach for mining uncertainty rules and filling missing values is proposed, which is in turn particularly suitable for dynamic databases, like the ones used in home care systems. METHODS: In this study, a new data mining method named FiMV (Filling Missing Values) is illustrated based on the mined uncertainty rules. Uncertainty rules have quite a similar structure to association rules and are extracted by an algorithm proposed in previous work, namely AURG (Adaptive Uncertainty Rule Generation). The main target was to implement an appropriate method for recovering missing values in a dynamic database, where new records are continuously added, without needing to specify any kind of thresholds beforehand. RESULTS: The method was applied to a home care monitoring system database. Randomly, multiple missing values for each record's attributes (rate 5-20% by 5% increments) were introduced in the initial dataset. FiMV demonstrated 100% completion rates with over 90% success in each case, while usual approaches, where all records with missing values are ignored or thresholds are required, experienced significantly reduced completion and success rates. CONCLUSIONS: It is concluded that the proposed method is appropriate for the data-cleaning step of the Knowledge Discovery process in databases. The latter, containing much significance for the output efficiency of any data mining technique, can improve the quality of the mined information.

Algorithms↗

PubMed1996

Sources of uncertainty in estimating HIV infection rates by back-calculation: an application to Italian data.

The effects on back-calculated HIV diffusion estimates of the uncertainties in a number of factors that may potentially influence the estimation process are examined and compared. More specifically, the effect on HIV infection estimates of uncertainties in: (i) the sequence of periodical AIDS incidence cases; (ii) the estimation of the AIDS incubation period, including the influence of therapeutic treatment on the same; and (iii) the choice of a particular back-calculation method, including the stochastic uncertainty associated with each method, are examined. The choice of one particular back-calculation model over another, among three different methods considered, seems to be a minor component of the uncertainty, when compared to the uncertainty, due to all other sources. HIV incidence and prevalence in Italy for different risk categories are estimated.

Algorithms↗

PubMed1979

Genetic counseling--the postcounseling period: I. Parents' perceptions of uncertainty.

To investigate how parents who have had genetic counseling perceive the problems created by being at risk, transcripts of open-ended, semistructured follow-up interviews with 53 counselees were analyzed qualitatively. Rate information, though recalled accurately by parents considering further childbearing, was discounted as impersonal, and subjects overwhelmingly perceived the chance of recurrence in binary form -- it either will or will not happen. By processing rates this way, they simplified probabilistic information and shifted their focus to the implications of being at risk and the potential impact of that which might or might not occur. The many uncertainties they faced, the "consequences" of being at risk that parents felt had to be resolved during the decision-making process, fell into 3 major categories: uncertainty that arose because of the ambiguous impact and meaning of having an affected child; uncertainty about how to make a choice and how others would view it, the burden of decision-making; and uncertainty about their ability to fulfill their roles as parents. These issues were perceived as part of the problem to be resolved and were consolidated into "scenarios" in which the parents "tried out the worst." This analysis of counselees' perceptions of the problems created by being at genetic risk suggests that parents may process the disparate facts of their situation in common ways that emphasize their uncertainty, and it indicates that how parents perceive factual information may be more important in orienting their deliberations than what these facts (diagnosis, prognosis, risks) actually are.

Decision Making↗

PubMed2005

Tolerance of uncertainty, extroversion, neuroticism and attitudes to randomized controlled trials among surgeons and physicians.

BACKGROUND: Surgeons have a reputation for decisiveness and self-confidence, which suggests that they may tolerate uncertainty poorly and therefore be less capable than other doctors of experiencing clinical equipoise. Their 'typical' behaviour is characteristic of the stable extrovert personality and so they may prefer spontaneous clinical judgement over randomized trials. The aim of this study was to compare personality dimensions and tolerance of uncertainty among surgeons and hospital physicians, to determine whether differences in either property might help to explain the apparently poor performance of surgeons in conducting randomized controlled trials. METHODS: This was a postal questionnaire study of 1000 consultant general surgeons and 1000 consultant physicians. Respondents completed a short self-assessment of Eysenck personality dimensions, Budner's Intolerance of Ambiguity scale and a short questionnaire about attitudes to randomized trials. Correlation and multiple regression analyses were performed. RESULTS: The response rate was 36.5 per cent. Physicians were more likely to be women (P < 0.001) and had spent 1 more year in academic posts than surgeons (P < 0.030). Surgeons were significantly more extrovert (P < 0.001) and less neurotic (P < 0.001) than physicians. Surgeons were significantly more intolerant of uncertainty than physicians (P = 0.007). Multivariate analysis identified age (P < 0.030) and sex (P = 0.015) as independent predictors of intolerance of uncertainty. The attitudes of surgeons and physicians to randomized trials were no different. CONCLUSION: Surgeons are not prejudiced against randomized trials, but their intolerance of uncertainty may inhibit them from deciding that an individual patient is suitable for trial entry. If more surgeons were female, this difference between surgeons and physicians might disappear.

Attitude of Health Personnel↗

PubMedDate not supplied

Uncertainty in the economic evaluation of health care technologies: the role of sensitivity analysis.

Given the increased use of economic evaluation to inform decision making in the health service, it is particularly important that the research methods used are critically assessed and, where possible, improved. The systematic handling of uncertainty in economic evaluation is an important area that remains methodologically underdeveloped. With the increased use of the clinical trial as a vehicle for economic evaluation, there has been recent interest in how the statistical methods routinely employed to handle uncertainty in clinical research might be applied to economic evaluation. This paper reviews the types of uncertainty that exist in economic evaluation and argues that some forms of uncertainty are not amenable to statistical methods. Sensitivity analysis is not a single approach but can take a number of different forms. The different types of sensitivity analysis are reviewed, with an indication of their strengths and weaknesses in relation to the different types of uncertainty in economic evaluation.

Cost-Benefit Analysis↗

PubMed2003

Determining and visualizing uncertainty in estimates of fiber orientation from diffusion tensor MRI.

Diffusion tensor MRI (DT-MRI) permits determination of the dominant orientation of structured tissue within an image voxel. This has led to the development of 2D graphical methods for representing fiber orientation and DT-MRI "tractography," which aims to reconstruct the 3D trajectories of white matter fasciculi. Most contemporary fiber orientation mapping schemes and tractography algorithms employ the directional information contained in the eigenvectors of the diffusion tensor to approximate white matter fiber orientation. However, while the uncertainty associated with every estimate of an eigenvector has long been recognized, no attempts to quantify this uncertainty in vivo have been reported. Here, a method is proposed for determining confidence intervals in fiber orientation from real DT-MRI data using the bootstrap method. This is used to construct maps of the "cone of uncertainty," allowing simultaneous viewing of fiber orientation and its uncertainty, and to examine the relationship between orientation uncertainty and tissue anisotropy.

Anisotropy↗

PubMed2004

The impact of an informational self-management intervention on the association between control and illness uncertainty before and psychological distress after radiotherapy.

Many studies have reported that cancer patients who show difficulties maintaining perceptions of control report more psychological distress than patients who are higher in control. Besides perceptions of control, feelings of illness uncertainty have also been regarded as a predictor of psychological distress. Given these strong relationships between perceptions of low control and high illness uncertainty and psychological distress, the present study examined whether an informational self-management intervention (booklet) could moderate this relationship. The booklet contained general and specific information about cancer and cancer treatment, information about possible coping strategies, and social comparison information, which consisted of short stories of other patients. Prior to radiotherapy, 209 patients with cancer completed baseline measures, including control and illness uncertainty. After completing radiotherapy, patients were randomly allocated to receive either a booklet (experimental group; N=103) or no booklet (control group; N=106). Three months after the intervention, aspects of psychological distress were assessed, including tension, anger, depression, fatigue and vigour. The results supported our hypotheses and suggested that a self-management intervention is relevant in reducing the relationship between control and illness uncertainty before radiotherapy and psychological distress after radiotherapy. This seems important, especially for high-risk patients who perceive little control and much illness uncertainty.

Adaptation, Psychological↗

PubMed2005

Benefits from an uncertainty management intervention for African-American and Caucasian older long-term breast cancer survivors.

In a randomized controlled design, this study tested the efficacy of a theoretically based uncertainty management intervention delivered to older long-term breast cancer survivors. The sample included 509 recurrence-free women (360 Caucasian, 149 African-American women) with a mean age of 64 years (S.D.=8.9 years) who were 5-9 years post-treated for breast cancer. Women were randomly assigned to either the intervention or usual care control condition. The intervention was delivered during four weekly telephone sessions, in which study nurses guided cancer survivors in the use of audiotaped cognitive-behavioral strategies to manage uncertainty about recurrence, and a self-help manual designed to help women understand and manage long-term treatment side effects and other symptoms. Treatment outcome data on uncertainty management were gathered at pre-intervention and 10-months afterward. Repeated measures MANOVA evaluating treatment group, ethnic group, and treatment by ethnic interaction effects indicated that training in uncertainty management resulted in improvements in cognitive reframing, cancer knowledge, patient-health care provider communication, and a variety of coping skills. Results are discussed in terms of the importance of theory-based interventions for cancer survivors that target triggers of uncertainty about recurrence and in terms of ethnic differences in response to the intervention.

Adaptation, Psychological↗