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Potential Outcomes (potential + outcome)
Selected AbstractsAnticipatory grieving among parents living with a child with cancerJOURNAL OF ADVANCED NURSING, Issue 9 2010Ekhlas Al-Gamal al-gamal e. & long t. (2010) Anticipatory grieving among parents living with a child with cancer. Journal of Advanced Nursing,66(9), 1980,1990. Abstract Aim., This paper is a report of a comparative study of anticipatory grief of parents of children newly diagnosed with cancer and those whose children were diagnosed 6,12 months earlier. Background., Public perceptions of cancer as a fatal illness persist despite improved prognosis for children. Parents may experience feelings of despair, hopelessness, and worthlessness , the most common psychological expressions of anticipatory grief. With a focus on developing more effective therapeutic intervention, healthcare professionals have developed greater interest in the concept of anticipatory grief. Method., One hundred and forty parents, divided between ,newly diagnosed' and ,6,12 months after diagnosis' groups, were recruited in 2006 from two hospitals representative of the healthcare sector in Jordan. Structured interviews were conducted to assess anticipatory grief, using the Marwit and Meuser Caregiver Inventory: Childhood Cancer. Analysis was performed using t -tests. Results., Fewer than half of the parents in both groups reported being at peace with themselves and their situation in life. Parents of newly diagnosed children reported more severe anticipatory grief responses than those in the second group. No statistically significant differences were found in responses between mothers and fathers. Conclusion., Healthcare professionals should encourage parents to discuss negative feelings related to their child's illness and potential outcome. Hospital policies need to include the provision and promotion of support group services for parents, and nurses should encourage parents to exploit such services. [source] KEYNOTE ADDRESS Ku80-deletion causes early ageing and suppresses cancerJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 2 2009P. Hasty Ageing is widespread cellular decline resulting in a loss of fitness that is both pleiotropic and stochastic and influenced by both genetics and environment. As a result the fundamental underling causes of ageing are diverse and controversial. One potential ageing target is nuclear DNA, as it is a permanent blueprint that controls cellular processes. Thus, DNA replication and genome maintenance are highly regulated events that ensure faithful reproduction and maintenance of the blueprint and these pathways assure sufficient longevity for reproduction and survival of the species. As a consequence, imperfections or defects in maintaining the genome may contribute to ageing. Therefore, genome maintenance pathways are longevity-assurance mechanisms that sustain an organism long enough to reproduce and propagate. Chief among these mechanisms are those that respond to damaged DNA. There are two basics responses to genomic damage: DNA repair and cell cycle checkpoints. Both are considered to be tumour suppressors and are categorized as either caretakers or gatekeepers, respectively. Interestingly, observations of human and mouse pre-mature ageing models suggest these anti-tumour pathways impact the ageing process. Caretakers suppress cancer by repairing DNA damage caused by defects in replication or by a variety of agents including endogenously produced reactive by-products of oxygen metabolism and exogenous agents naturally encountered in our environment. As a consequence DNA is subject to a variety of insults that cause a diverse range of lesions and phenotypic outcomes. There are many forms of DNA damage including base lesions and double-strand breaks (DSBs) with the latter being more toxic. Cancer-causing chromosomal rearrangements may result if DSBs are not repaired properly. Additionally, an accumulation of these rearrangements may contribute to ageing since they increase in some cell types as humans and mice age. Furthermore, early ageing models suggest that defects in repairing DSBs lead to early ageing in humans and mice. Non-homologous end joining (NHEJ) is an important pathway for repairing DNA DSBs and is considered a caretaker. The Ku heterodimer (composed of Ku70 and Ku80) binds to DNA ends to initiate NHEJ, and defects in either Ku70 or Ku80 lead to increased levels of DNA DSBs and chromosomal rearrangements, leading many to believe Ku is a caretaker. Ku-mutant mice display increased GCRs, but without increased cancer. Instead, these mice show early ageing and shortened life span. Thus, Ku's role as a caretaker is uncertain as the low cancer levels may be due to Ku80-deletion or, instead, the low cancer levels may simply be a consequence of the shortened life span that prohibits sufficient time for tumours to develop. Gatekeepers respond to DNA damage by halting the cell cycle long enough for the DNA to be repaired. If the damage is irreparable, gatekeepers induce either apoptosis or senescence. These responses are deleterious to the cell but protect the organism from cancer as one potential outcome of genetic mutations is uncontrolled proliferation. p53 is critical for checkpoints and is the best-known gatekeeper because it is mutated in over half of all cancers. In addition, p53 activity influences many aspects of the Ku-mutant phenotype suggesting that Ku-deletion leads to persistent p53-mediated responses and presenting the possibility that low cancer levels and early ageing are caused by elevated gatekeeper responses. Our hypothesis is that Ku-mutant mice exhibit low cancer levels and, perhaps, ageing due to persistent p53-mediated responses to inefficiently repaired DNA. To test this hypothesis, Ku80-mutant mice were crossed to cancer-prone mice with either non-functional or functional gatekeeper responses. Ku80-mutant mice were crossed to p53-mutant mice to determine if Ku80-deletion exacerbates oncogenesis when gatekeeper responses are diminished. Ku80-mutant mice deleted for p53 exhibit early onset and high levels of two forms of cancer: pro-B cell lymphoma and medulloblastoma, thus supporting the hypothesis. Ku80-mutant mice were also crossed to APCMIN mice to determine if Ku80-deletion ameliorates oncogenesis gatekeeper responses are intact. APCMIN mice exhibit high levels of intestinal adenomas and adenocarcinomas but have normal p53-mediated responses to DNA damage. APCMIN mice, deleted for Ku80, exhibit about 67% fewer tumours than APCMIN mice with Ku80. Thus, deletion of Ku80 suppresses tumour formation, again supporting the hypothesis. Ku80-mutant cells and tissues were tested for p53-mediated DNA damage responses, levels of DNA damage, and mutations. Ku80-mutant fibroblasts exhibit elevated levels of p53-mediated DNA damage responses that increase p21-mediated cellular senescence. In addition, there are elevated levels DNA damage as seen by increased 53BP1 foci and elevated levels of chromosomal rearrangements. Thus, these data support the hypothesis that Ku80-deletion reduces tumors by elevating DNA damage gatekeeper responses to inefficiently repaired DNA. These data also support the possibility that the Ku80-mutant ageing phenotype is also due to elevated gatekeeper responses. [source] Computer Imaging versus Conventional Esthetic Consultation: A Prospective Clinical StudyJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 2 2000OLGA S. PAPASOTIRIOU DMD ABSTRACT Computer imaging can be helpful in demonstrating to patients the potential outcome of esthetic dental procedures. The current clinical study assesses the effectiveness of computer imaging by comparing the reactions of patient and dentist to conventional consultations versus the use of computer imaging. The responses from 35 subjects show that computer imaging consultations are more effective in helping patients decide to accept treatment. Patient satisfaction was higher (93.75%) with computer consultations than with conventional methods (83.3%). Computer imaging consultations were easier to conduct but significantly (p < .05) more time consuming. CLINICAL SIGNIFICANCE This experiment confirms the role of computer imaging as an effective aid in esthetic dentistry consultations and treatment planning. Imaging facilitates communication between patient and practitioner and provides a more realistic view of anticipated treatment outcomes. [source] Information for inspiration: Understanding architects' information seeking and use behaviors to inform designJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 9 2010Stephann Makri Architectural design projects are heavily reliant on electronic information seeking. However, there have been few studies on how architects look for and use information on the Web. We examined the electronic information behavior of 9 postgraduate architectural design and urban design students. We observed them undertake a self-chosen, naturalistic information task related to one of their design projects and found that although the architectural students performed many similar interactive information behaviors to academics and practitioners in other disciplines, they also performed behaviors reflective of the nature of their domain. The included exploring and encountering information (in addition to searching and browsing for it) and visualizing/appropriating information. The observations also highlighted the importance of information use behaviors (such as editing and recording) and communication behaviors (such as sharing and distributing) as well as the importance of multimedia materials, particularly images, for architectural design projects. A key overarching theme was that inspiration was found to be both an important driver for and potential outcome of information work in the architecture domain, suggesting the need to design electronic information tools for architects that encourage and foster creativity. We make suggestions for the design of such tools based on our findings. [source] Influence of insulin resistance on hepatic fibrosis and steatosis in hepatitis C virus (HCV) mono-infected compared with HIV,HCV co-infected patientsALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 1 2009P. HALFON Summary Background, Insulin resistance (IR), the major feature of the metabolic syndrome, is also common in patients with chronic HCV infection. Liver fibrosis and steatosis are known potential outcome of chronic hepatitis B or C infection. Studies have shown that HIV positive individuals co-infected with HCV have more rapid live disease progression than those with HIV alone. Few data have reported the influence of IR on steatosis and fibrosis in the context of HIV-HCV coinfection. Aim, To test the association among insulin resistance (IR), liver fibrosis and liver steatosis in HIV,HCV and HCV-infected patients. Patients and methods, A total of 170 HIV,HCV-infected patients matched by age, gender and genotype with 170 HCV mono-infected patients were included. Patients were considered to be IR when the homeostasis model assessment of IR >2. Significant fibrosis was considered if METAVIR ,F2 and significant steatosis if ,10%. Results, Insulin resistance was independently associated in HCV patients with fibrosis [odds ratio (OR) = 2.04 (95% CI 1.02,4)], a body mass index (BMI) >25 kg/m² [OR = 3.33 (1.47,7.69)] and steatosis [OR = 3.33 (1.67,6.67)]. Fibrosis ,F2 was associated in HCV patients with high liver activity grade (,A2) [OR = 8.33 (3.85,16.67)], male gender [OR = 3.03 (1.33,7.14)] and IR [OR = 2.44 (1.15,5)]. In HIV,HCV patients, ,A2 [OR = 5.56 (1.64,20)] was associated with fibrosis. Steatosis ,10% was associated in HCV patients with IR [OR = 3.13 (1.59,6.25) and ,F2 (OR = 2.22 (1.15,4.17)]. In HIV,HCV, a BMI >25 kg/m² [OR = 3.85 (1.64,9.10)], ,A2 [OR = 2.16 (1.02,4.55); P = 0.044] and nucleoside reverse transcriptase inhibitor [OR = 3.61 (1.19,10.96); P = 0.023] were independently associated with significant liver steatosis. Conclusions, Insulin resistance is associated with liver fibrosis and steatosis in HCV mono-infected, but not in HIV,HCV co-infected patients. Significant liver fibrosis is associated with IR independent of liver steatosis only in HCV mono-infected patients. [source] Gender equality or patriarchal dividend: Structural change in Turkish nursingNURSING & HEALTH SCIENCES, Issue 2 2008Elizabeth Herdman rn, bsocsc Abstract Turkey is attempting to join the European Union and is facing pressure to eliminate many forms of discrimination, including discrimination based on gender. In keeping with these aims, in early 2007 the Turkish government changed the law to permit Turkish men to become nurses. Given that Turkey is a highly patriarchal society and that occupational segregation by sex is a persistent feature, it is important to examine the potential outcome of the legislative changes. The aim of this paper is to explore the paradoxical potential for Turkish female nurses to experience increased discrimination in a system that is restructured by legislation to be non-discriminatory. [source] Autoindexing the diffraction patterns from crystals with a pseudotranslationACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2009Nicholas K. Sauter Rotation photographs can be readily indexed if enough candidate Bragg spots are identified to properly sample the reciprocal lattice. However, while automatic indexing algorithms are widely used for macromolecular data processing, they can produce incorrect results in special situations where a subset of Bragg spots is systematically overlooked. This is a potential outcome in cases where a noncrystallographic translational symmetry operator closely mimics an exact crystallographic translation. In these cases, a visual inspection of the diffraction image will reveal alternating strong and weak reflections. However, reliable detection of the weak-intensity reflections by software requires a systematic search for a diffraction signal targeted at specific reciprocal-space locations calculated a priori by considering all possible pseudotranslations. Care must be exercised to distinguish between true lattice diffraction and spurious signals contributed by neighboring overlapping Bragg spots, non-Bragg diffraction and noise. Such procedures have been implemented within the autoindexing program LABELIT and applied to known cases from publicly available data sets. Routine use of this type of signal search adds only a few seconds to the typical run time for autoindexing. The program can be downloaded from http://cci.lbl.gov/labelit. [source] An intelligent logistics support system for enhancing the airfreight forwarding businessEXPERT SYSTEMS, Issue 5 2004H.C.W. Lau Abstract: Recent research related to the aircraft container loading and scheduling problem for airfreight forwarding business has seen significant advances in terms of load plan optimization, taking into account the cost and volume of packed boxes. In today's competitive industrial environment, it is essential that freight forwarders are able to collaborate with carriers (airline companies) to achieve the best possible selection of logistics workflow. However, study of contemporary research publications indicates that there is a dearth of articles related to the design and implementation of an intelligent logistics system to support decision-making on carrier selection, aircraft container loading plans as well as carrier benchmarking. This paper presents an intelligent logistics support system (ILSS) which is able to provide expert advice related to the airfreight forwarding business, enhancing the logistics operations in relevant activities within the value chain of tasks. ILSS comprises a heuristics-based intelligent expert system which supports carrier searching and cargo trading planning as well as load plan generation. The proposed approach is meant to enhance various operations in the airfreight forwarding business, adopting computational intelligence technologies such as rule-based reasoning to provide domain advice and heuristics to support the generation of load plans. After potential outcomes are generated by the heuristics-based intelligent expert system, a neural network engine is applied to support prediction of unexpected events. To validate the viability of this approach, a production system using the ILSS has been developed and subsequently applied in an emulated airfreight forwarding environment. The application results indicate that the operation time from searching for potential carriers to the execution of the order is greatly reduced. In this paper, details related to the structure, design and implementation of the ILSS are also covered with the inclusion of the actual program codes for building the prototype. [source] Quality of private personal care for elderly people with a disability living at home: correlates and potential outcomesHEALTH & SOCIAL CARE IN THE COMMUNITY, Issue 4 2008Claudio Bilotta MD Abstract To investigate correlates of the quality of private personal care for community-dwelling elderly people, this cross-sectional study enrolled 100 elderly outpatients living at home, along with their private aides and 88 informal caregivers, from May 2005 to January 2007. Cases were stratified according to the quality of private care as was described by both elderly participants and informal caregivers. In cases where the elderly person was suffering from overt cognitive impairment, only the opinions of the informal caregivers were taken into account. A comparison was made between the ,poor or fair care' group (n = 16), the ,intermediate care' group (n = 39) and the ,optimal care' group (n = 45). Considering the characteristics of private aides, there was a significant trend across the three groups in terms of language skills (P = 0.002) and level of distress with life conditions (P = 0.020). A statistical analysis performed on elderly participants without an overt cognitive impairment (n = 59) and informal caregivers showed an increase in the European Quality of Life Visual Analogue Scale score in the elderly group [mean ± standard deviation (SD) were, respectively, 45 ± 23.2, 63.7 ± 19.7 and 68.8 ± 21.6; P = 0.007], and a decrease in the Caregiver Burden Inventory score (mean ± SD were, respectively, 34.9 ± 25.3, 26 ± 17.7 and 17.6 ± 14.6; P = 0.020) across the three groups. We found no significant difference between elderly people in the three groups in terms of social variables, functional and cognitive status, prevalence of depressive disorders and morbidity. Therefore, good language skills and non-distressing life conditions of private aides appeared to be correlates of an optimal quality of care for community-dwelling elderly people with a disability, and also a better quality of life for them and less distress for their informal caregivers appeared to be potential outcomes of the quality of personal care. [source] Refining the stress-gradient hypothesis for competition and facilitation in plant communitiesJOURNAL OF ECOLOGY, Issue 2 2009Fernando T. Maestre Summary 1The stress-gradient hypothesis (SGH) predicts that the frequency of facilitative and competitive interactions will vary inversely across abiotic stress gradients, with facilitation being more common in conditions of high abiotic stress relative to more benign abiotic conditions. With notable exceptions, most tests of the SGH have studied the interaction between a single pair or a few pairs of species, and thus have evaluated shifts in the magnitude and direction of pair-wise interactions along stress gradients, rather than shifts in the general frequency of interactions. 2The SGH has been supported by numerous studies in many ecosystems, has provided a crucial foundation for studying the interplay between facilitation and competition in plant communities, and has a high heuristic value. However, recent empirical research indicates that factors like the variation among species and the nature of the stress gradient studied add complexity not considered in the SGH, creating an opportunity to extend the SGH's general conceptual framework. 3We suggest that one approach for extending the SGH framework is to differentiate between the original idea of how ,common' interactions might be along stress gradients and the ubiquitous empirical approach of studying shifts in the strength of pair-wise interactions. Furthermore, by explicitly considering the life history of the interacting species (relative tolerance to stress vs. competitive ability) and the characteristics of the stress factor (resource vs. non-resource) we may be able to greatly refine specific predictions relevant to the SGH. 4We propose that the general pattern predicted by the SGH would hold more frequently for some combinations of life histories and stress factor, particularly when the benefactor and beneficiary species are mostly competitive and stress-tolerant, respectively. However, we also predict that other combinations are likely to yield different results. For example, the effect of neighbours can be negative at both ends of the stress gradient when both interacting species have similar ,competitive' or ,stress-tolerant' life histories and the abiotic stress gradient is driven by a resource (e.g. water). 5Synthesis. The extension of the SGH presented here provides specific and testable hypotheses to foster research and helps to reconcile potential discrepancies among previous studies. It represents an important step in incorporating the complexity and species-specificity of potential outcomes into models and theories addressing how plant,plant interactions change along stress gradients. [source] A Unique Set of Interactions: The MSU Sustained Partnership Model of Nurse Practitioner Primary CareJOURNAL OF THE AMERICAN ACADEMY OF NURSE PRACTITIONERS, Issue 2 2004FNP Assistant Professor, Katherine Dontje MSN Purpose To present a unified conceptual model that identifies the integral processes of nurse practitioner (NP) care delivery and that integrates major structural influences and potential outcomes. The model is further characterized to delineate the unique and "value-added" nature of NP primary care and to describe how this nature may be correlated with specific clinical outcomes. Data Sources Extensive review of the literature, relevant conceptual models, clinical experiences of the authors, and two sets of qualitative data exploring differences between NP practice and other practices. Conclusions The basis of NP primary care is the unique provider-client relationship that develops within the primary care setting. This relationship is oriented toward (a) helping clients become empowered to more appropriately manage their own care in a way that will best meet their needs, (b) encouraging mutual decision making, (c) ensuring clients' continuity of care, and (d) providing a holistic approach to primary care. The major structural influences are NP role components, interdisciplinary practice relationships, budget resources and payer mix, and environmental characteristics. The potential outcomes are increased healthpromoting behaviors, improved utilization of care, higher client satisfaction levels, and improved health status. Implications for Practice NPs can use this model to articulate the unique contribution of NP practice and its interrelationships within the broader primary care setting. Practicing NPs can use this framework to better understand the complexities of their current and future primary care practices. Faculty can utilize the concepts to help guide students' understanding of their prospective roles as advanced practice nurses. Finally, this conceptual framework can inform research about specific NP processes and related outcomes. A clearly delineated model that accurately depicts structures, processes, and outcomes relevant to NP primary care can strengthen NP education, distinguish NP practice, and advance evidenced-based research linking NP practice and outcomes. [source] Models, Assumptions, and Stakeholders: Planning for Water Supply Variability in the Colorado River Basin,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2008Dustin Garrick Abstract:, Declining reservoir storage has raised the specter of the first water shortage on the Lower Colorado River since the completion of Glen Canyon and Hoover Dams. This focusing event spurred modeling efforts to frame alternatives for managing the reservoir system during prolonged droughts. This paper addresses the management challenges that arise when using modeling tools to manage water scarcity under variable hydroclimatology, shifting use patterns, and institutional complexity. Assumptions specified in modeling simulations are an integral feature of public processes. The policymaking and management implications of assumptions are examined by analyzing four interacting sources of physical and institutional uncertainty: inflow (runoff), depletion (water use), operating rules, and initial reservoir conditions. A review of planning documents and model reports generated during two recent processes to plan for surplus and shortage in the Colorado River demonstrates that modeling tools become useful to stakeholders by clarifying the impacts of modeling assumptions at several temporal and spatial scales. A high reservoir storage-to-runoff ratio elevates the importance of assumptions regarding initial reservoir conditions over the three-year outlook used to assess the likelihood of reaching surplus and shortage triggers. An ensemble of initial condition predictions can provide more robust initial conditions estimates. This paper concludes that water managers require model outputs that encompass a full range of future potential outcomes, including best and worst cases. Further research into methods of representing and communicating about hydrologic and institutional uncertainty in model outputs will help water managers and other stakeholders to assess tradeoffs when planning for water supply variability. [source] Optimal dynamic treatment regimesJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 2 2003S. A. Murphy Summary. A dynamic treatment regime is a list of decision rules, one per time interval, for how the level of treatment will be tailored through time to an individual's changing status. The goal of this paper is to use experimental or observational data to estimate decision regimes that result in a maximal mean response. To explicate our objective and to state the assumptions, we use the potential outcomes model. The method proposed makes smooth parametric assumptions only on quantities that are directly relevant to the goal of estimating the optimal rules. We illustrate the methodology proposed via a small simulation. [source] A hierarchical modelling approach to analysing longitudinal data with drop-out and non-compliance, with application to an equivalence trial in paediatric acquired immune deficiency syndromeJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2002Joseph W Hogan Longitudinal clinical trials with long follow-up periods almost invariably suffer from a loss to follow-up and non-compliance with the assigned therapy. An example is protocol 128 of the AIDS Clinical Trials Group, a 5-year equivalency trial comparing reduced dose zidovudine with the standard dose for treatment of paediatric acquired immune deficiency syndrome patients. This study compared responses to treatment by using both clinical and cognitive outcomes. The cognitive outcomes are of particular interest because the effects of human immunodeficiency virus infection of the central nervous system can be more acute in children than in adults. We formulate and apply a Bayesian hierarchical model to estimate both the intent-to-treat effect and the average causal effect of reducing the prescribed dose of zidovudine by 50%. The intent-to-treat effect quantifies the causal effect of assigning the lower dose, whereas the average causal effect represents the causal effect of actually taking the lower dose. We adopt a potential outcomes framework where, for each individual, we assume the existence of a different potential outcomes process at each level of time spent on treatment. The joint distribution of the potential outcomes and the time spent on assigned treatment is formulated using a hierarchical model: the potential outcomes distribution is given at the first level, and dependence between the outcomes and time on treatment is specified at the second level by linking the time on treatment to subject-specific effects that characterize the potential outcomes processes. Several distributional and structural assumptions are used to identify the model from observed data, and these are described in detail. A detailed analysis of AIDS Clinical Trials Group protocol 128 is given; inference about both the intent-to-treat effect and average causal effect indicate a high probability of dose equivalence with respect to cognitive functioning. [source] A scalar analysis of landscape connectivityOIKOS, Issue 2 2003Article first published online: 4 JUL 200 Landscape connectivity is critical to the maintenance of spatially-structured populations and consists of both a structural component, which describes the shape, size and location of landscape features; and a biological component, which consists of both the response of individuals to landscape features, and the patterns of gene flow that result from those individual responses. Traditional studies of landscape connectivity have attempted to discern individual behavioral responses to landscape features, but this methodology is intractable for many species. This paper is an attempt to relate the components of landscape connectivity through the explicit treatment of their spatial and temporal scales. Traditional measures of structural and biological components of connectivity are reviewed and more recently developed methods for the analysis of scale for each are introduced. I then present a framework for the comparison of scalar phenomena based on Watt's unit pattern, describe the potential outcomes of the comparison and discuss the implications of each. Several testable hypotheses emerge from the analysis that may serve as a useful framework for the investigation of landscape connectivity in the future. [source] The development of risk criteria for high severity low frequency events,PROCESS SAFETY PROGRESS, Issue 1 2009Fred Henselwood Abstract Quantitative risk assessments (QRAs) are used within the field of process safety to decide the allocation of resources and risk reduction investments. Typically risk assessments involve the evaluation of probabilistic measures that estimate the average expected value for the situation being considered across a range of potential outcomes. The resulting expected value is then used to determine if a situation represents an acceptable or unacceptable risk based on a threshold value allotted to the risk. This approach often gives guidance that is at odds with the thoughts and behaviors of some stakeholders as illustrated by the "but what if it does happen?" type of question. This inconsistency results from the inherent limitation associated with expected value approaches in that the methodology is based on whether or not a mean assessed risk represents an acceptable risk while overlooking the possibility that a single scenario could represent an intolerable event. This article looks at an adjustment to traditional QRAs so as to assess both the acceptability of risk and the tolerability of the associated consequences relative to risk criteria. These adjustments have been found to better represent stakeholder perceptions of risk, more closely relate risk tolerance to corporate values and resources, and to better justify the use of various risk transfer strategies. © 2008 American Institute of Chemical Engineers Process Saf Prog, 2009 [source] Computer-assisted implantology: historical background and potential outcomes,a reviewTHE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 2 2008Abbas Azari Abstract Background The accurate transfer of preoperatively determined implant positions to the patient mouth is very beneficial to the dental practitioner as well as patients. The objective of this paper was to review the gradual development of computer-assisted implant surgery. Methods All of the major data sources including unpublished data in the internet are considered Results and Conclusions Computer-assisted/-guided/-aided implantology has been founded to overcome the errors encountered during implant osteotomies and to position the implants more precisely. The protocols followed by this sophisticated technique are based upon the advocated concept of prosthetic-driven implantology and CT-scan analysis recently approved. Although several attempts have been made to improve this approach more and more, little has been done regarding the patient's demands, including cost. The inherent complexity of the techniques and materials utilized necessitates several degrees of training before attempting treatment and must be taken into account. Copyright © 2008 John Wiley & Sons, Ltd. [source] A Generalized Estimator of the Attributable Benefit of an Optimal Treatment RegimeBIOMETRICS, Issue 2 2010Jason Brinkley Summary For many diseases where there are several treatment options often there is no consensus on the best treatment to give individual patients. In such cases, it may be necessary to define a strategy for treatment assignment; that is, an algorithm that dictates the treatment an individual should receive based on their measured characteristics. Such a strategy or algorithm is also referred to as a treatment regime. The optimal treatment regime is the strategy that would provide the most public health benefit by minimizing as many poor outcomes as possible. Using a measure that is a generalization of attributable risk (AR) and notions of potential outcomes, we derive an estimator for the proportion of events that could have been prevented had the optimal treatment regime been implemented. Traditional AR studies look at the added risk that can be attributed to exposure of some contaminant; here we will instead study the benefit that can be attributed to using the optimal treatment strategy. We will show how regression models can be used to estimate the optimal treatment strategy and the attributable benefit of that strategy. We also derive the large sample properties of this estimator. As a motivating example, we will apply our methods to an observational study of 3856 patients treated at the Duke University Medical Center with prior coronary artery bypass graft surgery and further heart-related problems requiring a catheterization. The patients may be treated with either medical therapy alone or a combination of medical therapy and percutaneous coronary intervention without a general consensus on which is the best treatment for individual patients. [source] A Bayesian Approach to Surrogacy Assessment Using Principal Stratification in Clinical TrialsBIOMETRICS, Issue 2 2010Yun Li Summary A surrogate marker (S) is a variable that can be measured earlier and often more easily than the true endpoint (T) in a clinical trial. Most previous research has been devoted to developing surrogacy measures to quantify how well,S,can replace,T,or examining the use of,S,in predicting the effect of a treatment (Z). However, the research often requires one to fit models for the distribution of,T,given,S,and,Z. It is well known that such models do not have causal interpretations because the models condition on a postrandomization variable,S. In this article, we directly model the relationship among,T,,S, and,Z,using a potential outcomes framework introduced by Frangakis and Rubin (2002,,Biometrics,58, 21,29). We propose a Bayesian estimation method to evaluate the causal probabilities associated with the cross-classification of the potential outcomes of,S,and,T,when,S,and,T,are both binary. We use a log-linear model to directly model the association between the potential outcomes of,S,and,T,through the odds ratios. The quantities derived from this approach always have causal interpretations. However, this causal model is not identifiable from the data without additional assumptions. To reduce the nonidentifiability problem and increase the precision of statistical inferences, we assume monotonicity and incorporate prior belief that is plausible in the surrogate context by using prior distributions. We also explore the relationship among the surrogacy measures based on traditional models and this counterfactual model. The method is applied to the data from a glaucoma treatment study. [source] Multiple Imputation Methods for Treatment Noncompliance and Nonresponse in Randomized Clinical TrialsBIOMETRICS, Issue 1 2009L. Taylor Summary Randomized clinical trials are a powerful tool for investigating causal treatment effects, but in human trials there are oftentimes problems of noncompliance which standard analyses, such as the intention-to-treat or as-treated analysis, either ignore or incorporate in such a way that the resulting estimand is no longer a causal effect. One alternative to these analyses is the complier average causal effect (CACE) which estimates the average causal treatment effect among a subpopulation that would comply under any treatment assigned. We focus on the setting of a randomized clinical trial with crossover treatment noncompliance (e.g., control subjects could receive the intervention and intervention subjects could receive the control) and outcome nonresponse. In this article, we develop estimators for the CACE using multiple imputation methods, which have been successfully applied to a wide variety of missing data problems, but have not yet been applied to the potential outcomes setting of causal inference. Using simulated data we investigate the finite sample properties of these estimators as well as of competing procedures in a simple setting. Finally we illustrate our methods using a real randomized encouragement design study on the effectiveness of the influenza vaccine. [source] Principal Stratification Designs to Estimate Input Data Missing Due to DeathBIOMETRICS, Issue 3 2007Constantine E. Frangakis Summary We consider studies of cohorts of individuals after a critical event, such as an injury, with the following characteristics. First, the studies are designed to measure "input" variables, which describe the period before the critical event, and to characterize the distribution of the input variables in the cohort. Second, the studies are designed to measure "output" variables, primarily mortality after the critical event, and to characterize the predictive (conditional) distribution of mortality given the input variables in the cohort. Such studies often possess the complication that the input data are missing for those who die shortly after the critical event because the data collection takes place after the event. Standard methods of dealing with the missing inputs, such as imputation or weighting methods based on an assumption of ignorable missingness, are known to be generally invalid when the missingness of inputs is nonignorable, that is, when the distribution of the inputs is different between those who die and those who live. To address this issue, we propose a novel design that obtains and uses information on an additional key variable,a treatment or externally controlled variable, which if set at its "effective" level, could have prevented the death of those who died. We show that the new design can be used to draw valid inferences for the marginal distribution of inputs in the entire cohort, and for the conditional distribution of mortality given the inputs, also in the entire cohort, even under nonignorable missingness. The crucial framework that we use is principal stratification based on the potential outcomes, here mortality under both levels of treatment. We also show using illustrative preliminary injury data that our approach can reveal results that are more reasonable than the results of standard methods, in relatively dramatic ways. Thus, our approach suggests that the routine collection of data on variables that could be used as possible treatments in such studies of inputs and mortality should become common. [source] Estimating Mean Response as a Function of Treatment Duration in an Observational Study, Where Duration May Be Informatively CensoredBIOMETRICS, Issue 2 2004Brent A. Johnson Summary. After a treatment is found to be effective in a clinical study, attention often focuses on the effect of treatment duration on outcome. Such an analysis facilitates recommendations on the most beneficial treatment duration. In many studies, the treatment duration, within certain limits, is left to the discretion of the investigators. It is often the case that treatment must be terminated prematurely due to an adverse event, in which case a recommended treatment duration is part of a policy that treats patients for a specified length of time or until a treatment-censoring event occurs, whichever comes first. Evaluating mean response for a particular treatment-duration policy from observational data is difficult due to censoring and the fact that it may not be reasonable to assume patients are prognostically similar across all treatment strategies. We propose an estimator for mean response as a function of treatment-duration policy under these conditions. The method uses potential outcomes and embodies assumptions that allow consistent estimation of the mean response. The estimator is evaluated through simulation studies and demonstrated by application to the ESPRIT infusion trial coordinated at Duke University Medical Center. [source] Addressing an Idiosyncrasy in Estimating Survival Curves Using Double Sampling in the Presence of Self-Selected Right CensoringBIOMETRICS, Issue 2 2001Constantine E. Frangakis Summary. We investigate the use of follow-up samples of individuals to estimate survival curves from studies that are subject to right censoring from two sources: (i) early termination of the study, namely, administrative censoring, or (ii) censoring due to lost data prior to administrative censoring, so-called dropout. We assume that, for the full cohort of individuals, administrative censoring times are independent of the subjects' inherent characteristics, including survival time. To address the loss to censoring due to dropout, which we allow to be possibly selective, we consider an intensive second phase of the study where a representative sample of the originally lost subjects is subsequently followed and their data recorded. As with double-sampling designs in survey methodology, the objective is to provide data on a representative subset of the dropouts. Despite assumed full response from the follow-up sample, we show that, in general in our setting, administrative censoring times are not independent of survival times within the two subgroups, nondropouts and sampled dropouts. As a result, the stratified Kaplan,Meier estimator is not appropriate for the cohort survival curve. Moreover, using the concept of potential outcomes, as opposed to observed outcomes, and thereby explicitly formulating the problem as a missing data problem, reveals and addresses these complications. We present an estimation method based on the likelihood of an easily observed subset of the data and study its properties analytically for large samples. We evaluate our method in a realistic situation by simulating data that match published margins on survival and dropout from an actual hip-replacement study. Limitations and extensions of our design and analytic method are discussed. [source] The impact of exposure to domestic violence on children and young people: a review of the literatureCHILD: CARE, HEALTH AND DEVELOPMENT, Issue 6 2008Richard Reading The impact of exposure to domestic violence on children and young people: a review of the literature HoltS., BuckleyH. & WhelanS. ( 2008 ) Child Abuse & Neglect , 32 , 797 , 810 . Objective This article reviews the literature concerning the impact of exposure to domestic violence on the health and developmental well-being of children and young people. Impact is explored across four separate yet interrelated domains (domestic violence exposure and child abuse, impact on parental capacity, impact on child and adolescent development and exposure to additional adversities), with potential outcomes and key messages concerning best practice responses to children's needs highlighted. Method A comprehensive search of identified databases was conducted within an 11-year framework (1995,2006). This yielded a vast literature that was selectively organized and analysed according to the four domains identified above. Results This review finds that children and adolescents living with domestic violence are at increased risk of experiencing emotional, physical and sexual abuse, of developing emotional and behavioural problems and of increased exposure to the presence of other adversities in their lives. It also highlights a range of protective factors that can mitigate against this impact, in particular a strong relationship with and attachment to a caring adult, usually the mother. Conclusion Children and young people may be significantly affected by living with domestic violence, and impact can endure even after measures have been taken to secure their safety. It also concludes that there is rarely a direct causal pathway leading to a particular outcome and that children are active in constructing their own social world. Implications for interventions suggest that timely, appropriate and individually tailored responses need to build on the resilient blocks in the child's life. Practice implications This study illustrate the links between exposure to domestic violence, various forms of child abuse and other related adversities, concluding that such exposure may have a differential yet potentially deleterious impact for children and young people. From a resilient perspective this review also highlights range of protective factors that influence the extent of the impact of exposure and the subsequent outcomes for the child. This review advocates for a holistic and child-centred approach to service delivery, derived from an informed assessment, designed to capture a picture of the individual child's experience and responsive to their individual needs. [source] | |||||||||||||||||||||||||