Home About us Contact
|
Home About us Contact | ||
|
|
||
Probability Assessment (probability + assessment)
Selected AbstractsEmergency Medicine Practitioner Knowledge and Use of Decision Rules for the Evaluation of Patients with Suspected Pulmonary Embolism: Variations by Practice Setting and Training LevelACADEMIC EMERGENCY MEDICINE, Issue 1 2007Michael S. Runyon MD Abstract Background Several clinical decision rules (CDRs) have been validated for pretest probability assessment of pulmonary embolism (PE), but the authors are unaware of any data quantifying and characterizing their use in emergency departments. Objectives To characterize clinicians' knowledge of and attitudes toward two commonly used CDRs for PE. Methods By using a modified Delphi approach, the authors developed a two-page paper survey including 15 multiple-choice questions. The questions were designed to determine the respondents' familiarity, frequency of use, and comprehension of the Canadian and Charlotte rules. The survey also queried the frequency of use of unstructured (gestalt) pretest probability assessment and reasons why physicians choose not to use decision rules. The surveys were sent to physicians, physician assistants, and medical students at 32 academic and community hospitals in the United States and the United Kingdom. Results Respondents included 555 clinicians; 443 (80%) work in academic practice, and 112 (20%) are community based. Significantly more academic practitioners (73%) than community practitioners (49%) indicated familiarity with at least one of the two decision rules. Among all respondents familiar with a rule, 50% reported using it in more than half of applicable cases. A significant number of these respondents could not correctly identify a key component of the rule (23% for the Charlotte rule and 43% for the Canadian rule). Fifty-seven percent of all respondents indicated use of gestalt rather than a decision rule in more than half of cases. Conclusions Academic clinicians were more likely to report familiarity with either of these two specific decision rules. Only one half of all clinicians reporting familiarity with the rules use them in more than 50% of applicable cases. Spontaneous recall of the specific elements of the rules was low to moderate. Future work should consider clinical gestalt in the evaluation of patients with possible PE. [source] Rapid risk assessment using probability of fracture nomographsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2009R. PENMETSA ABSTRACT Traditional risk-based design process involves designing the structure based on risk estimates obtained during several iterations of an optimization routine. This approach is computationally expensive for large-scale aircraft structural systems. Therefore, this paper introduces the concept of risk-based design plots that can be used for both structural sizing and risk assessment for fracture strength when maximum allowable crack length is available. In situations when crack length is defined as a probability distribution the presented approach can only be applied for various percentiles of crack lengths. These plots are obtained using normalized probability density models of load and material properties and are applicable for any arbitrary load and strength values. Risk-based design plots serve as a tool for failure probability assessment given geometry and applied load or they can determine geometric constraints to be used in sizing given allowable failure probability. This approach would transform a reliability-based optimization problem into a deterministic optimization problem with geometric constraints that implicitly incorporate risk into the design. In this paper, cracked flat plate and stiffened plate are used to demonstrate the methodology and its applicability. [source] Contemporary management of pulmonary embolism: the answers to ten questionsJOURNAL OF INTERNAL MEDICINE, Issue 3 2010H. Bounameaux Abstract., Bounameaux H (Division of Angiology and Hemostasis, Department of Internal Medicine, University Hospitals of Geneva and Faculty of Medicine, Geneva, Switzerland). Contemporary management of pulmonary embolism: the answers to ten questions (Review). J Intern Med 2010; 268: 218,231. Pulmonary embolism (PE) cannot be diagnosed solely on a clinical basis, because of the lack of sensitivity and specificity of clinical signs and symptoms. Pulmonary angiography is invasive and resource demanding. Because the prevalence of PE is relatively low (20% or less) amongst individuals who are clinically suspected of having the disease, submitting all of them to imaging (multi-detector CT angiography or ventilation/perfusion lung scintigraphy) would not be cost-effective. Therefore, diagnostic algorithms have been developed that include clinical probability assessment and D-dimer measurement to select the patients who require noninvasive imaging. Once the diagnosis is suspected or confirmed, therapy must be started to avoid potentially fatal recurrence. Treatment starts for an initial 3-month period with a 5-day course of parenteral unfractionated or low-molecular-weight heparin or fondaparinux overlapping with and followed by oral vitamin K antagonists monitored to maintain an international normalized ratio of 2,3. This initial period of 3 months may then be followed by a long-term secondary prevention period in patients who experience an idiopathic thromboembolic event and are at low risk of bleeding. New oral anticoagulants that do require patient monitoring and might exhibit a more favourable benefit,risk balance are currently under extensive clinical testing and might change the situation in the near future. A critical appraisal of the contemporary management of suspected PE is given in this overview with the discussion of 10 practical questions. [source] The ,heuristics and biases' bias in expert elicitationJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2008Mary Kynn Summary., In the early 1970s Tversky and Kahneman published a series of papers on ,heuristics and biases' describing human inadequacies in assessing probabilities, culminating in a highly popular article in Science. This seminal research has been heavily cited in many fields, including statistics, as the definitive research on probability assessment. Curiously, although this work was debated at the time and more recent work has largely refuted many of the claims, this apparent heuristics and biases bias in elicitation research has gone unremarked. Over a decade of research into the frequency effect, the importance of framing, and cognitive models more generally, has been almost completely ignored by the statistical literature on expert elicitation. To remedy this situation, this review offers a guide to the psychological research on assessing probabilities, both old and new, and gives concrete guidelines for eliciting expert knowledge. [source] Differences in clinical presentation of deep vein thrombosis in men and womenJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2008E. ROSEANN ANDREOU Summary.,Background:,As assessment of clinical pretest probability is the first step in the diagnostic evaluation of deep vein thrombosis (DVT), it is important to know if the clinical features of DVT are the same in men and women. Objectives:,To compare the prevalence and clinical characteristics of DVT, and the accuracy of clinical pretest probability assessment, between men and women with suspected DVT. Methods:,A retrospective analysis of individual patient data from three prospective studies by our group that evaluated diagnostic tests for a suspected first episode of DVT. Clinical characteristics, clinical pretest probability for DVT, and prevalence and extent of DVT was assessed in a total of 1838 outpatients. Results:,The overall prevalence of DVT was higher in men than in women (14.4% vs. 9.4%) (P = 0.001). The prevalence of DVT was higher in men than in women who were categorized as having a clinical pretest probability that was low (6.9% vs. 3.5%; P = 0.025) or moderate (16.9% vs. 8.7%; P = 0.04), but similar in patients in the high category (40.2% vs. 44.0%; P = 0.6). In patients diagnosed with DVT, swelling of the entire leg occurred more often (41.5% vs. 15.7%; P < 0.001), and thrombosis was more extensive (involvement of both popliteal and common femoral veins in 47.9% vs. 21.6%), in women than in men. Conclusions:,In outpatients with suspected DVT, the overall prevalence of thrombosis and the prevalence of thrombosis in those with a low or a moderate clinical pretest probability were higher in men than in women. [source] Clinical probability and alveolar dead space measurement for suspected pulmonary embolism in patients with an abnormal D-dimer test resultJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 7 2006O. SANCHEZ Summary.,Background: Most patients with suspected pulmonary embolism (PE) have a positive D-dimer test and undergo diagnostic imaging. Additional non-invasive bedside tests are required to reduce the need for further diagnostic tests. Objectives: We aimed to determine whether a combination of clinical probability assessment and alveolar dead space fraction measurement can confirm or exclude PE in patients with an abnormal D-dimer test. Methods: We assessed clinical probability of PE and alveolar dead space fraction in 270 consecutive in- and outpatients with suspected PE and positive D-dimer. An alveolar dead space fraction < 0.15 was considered normal. PE was subsequently excluded or confirmed by venous compression ultrasonography, spiral computed tomography and a 3-month follow-up. Radiologists were unaware of the results of clinical probability and capnography. Results: PE was confirmed in 108 patients (40%). Capnography had a sensitivity of 68.5% (95% confidence interval [CI]: 58.9,77.1%) and a specificity of 81.5% (95% CI: 74.6,87.1%) for PE. Forty-five patients (16.6%) had both a low clinical probability and normal capnography (sensitivity: 99.1%, 95% CI: 94.9,100%) and 34 patients (12.6%) had both a high clinical probability and abnormal capnography (specificity: 100%, 95% CI: 97.7,100%). Conclusion: Capnography alone does not exclude PE accurately. The combination of clinical probability and capnography accurately excludes or confirms PE and avoids further testing in up to 30% of patients. [source] The utility of pretest probability assessment in patients with clinically suspected venous thromboembolismJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 9 2003J. Kelly Summary. ,The assessment of pretest probability (PTP), with stratification into low-, intermediate- and high-risk groups is an essential initial step in the current diagnostic management of patients with suspected venous thromboembolism (VTE). In combination with additional information, it reduces the need for initial and supplementary imaging, and allows considerable refinement of the posterior probability of VTE following non-invasive imaging. PTP may be assessed either empirically or by using various decision rules or scoring systems, the best known of which are the simplified Wells scores for suspected deep vein thrombosis (DVT) and pulmonary embolism (PE), and the Geneva score for suspected PE. Each of these approaches shows similar directional and categorical accuracy, and has been validated as facilitating clinically useful classification of the PTP, although an overview of data suggests that fewer patients tend to be classified as low PTP when assessed empirically. This group is the most important to identify, as several outcome studies have shown that imaging and treatment are safely obviated in outpatients with suspected DVT or PE who have a low PTP in combination with negative d -dimer testing, a subgroup accounting for up to half of all patients studied. Hence, while probably not of critical importance, the explicit approach offered by scoring systems might be preferred over empirical assessment, particularly when used by more junior staff. [source] Theory Comparison: Uncertainty Reduction, Problematic Integration, Uncertainty Management, and Other Curious ConstructsJOURNAL OF COMMUNICATION, Issue 3 2001James J. Bradac This paper compares 3 theories examining the role of communication in producing and coping with subjective uncertainty. Uncertainty reduction theory offers axioms and derived theorems that describe communicative and noncommunicative causes and consequences of uncertainty. The narrow scope of the theory and its axiomatic form are both advantageous and disadvantageous. Problematic integration and uncertainty management theories are comparatively broad, and they exhibit an open, web-like structure. The former theory scrutinizes the complex intersection of probability assessments and evaluations of the objects of these assessments, whereas the latter examines the various ways in which people cope with uncertainty, including sometimes attempting to increase it. The paper also compares meanings of "uncertainty" in the 3 theories as well as the roles played by natural language in the communication-uncertainty interface. [source] PROBabilities from EXemplars (PROBEX): a "lazy" algorithm for probabilistic inference from generic knowledgeCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 5 2002Peter Juslin Abstract PROBEX (PROBabilities from EXemplars), a model of probabilistic inference and probability judgment based on generic knowledge is presented. Its properties are that: (a) it provides an exemplar model satisfying bounded rationality; (b) it is a "lazy" algorithm that presumes no pre-computed abstractions; (c) it implements a hybrid-representation, similarity-graded probability. We investigate the ecological rationality of PROBEX and find that it compares favorably with Take-The-Best and multiple regression (Gigerenzer, Todd, & the ABC Research Group, 1999). PROBEX is fitted to the point estimates, decisions, and probability assessments by human participants. The best fit is obtained for a version that weights frequency heavily and retrieves only two exemplars. It is proposed that PROBEX implements speed and frugality in a psychologically plausible way. [source] | ||||||||||