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At least 487 records · Page 27Linked to original sources
PubMed2000

Neural network modeling of risk assessment in child protective services.

The advantages of using neural network methodology for the modeling of complex social science data are demonstrated, and neural network analysis is applied to Washington State Child Protective Services risk assessment data. Neural network modeling of the association between social worker overall assessment of risk and the 37 separate risk factors from the State of Washington Risk Assessment Matrix is shown to provide case classification results superior to linear or logistic multiple regression. The improvement in case prediction and classification accuracy is attributed to the superiority of neural networks for modeling nonlinear relationships between interacting variables; in this respect the mathematical framework of neural networks is a better approximation to the actual process of human decision making than linear, main effects regression. The implications of this modeling advantage for evaluating social science data within the framework of ecological theories are discussed.

Child↗
PubMed1998

Pravastatin. A pharmacoeconomic review of its use in primary and secondary prevention of coronary heart disease.

UNLABELLED: Coronary heart disease (CHD) is a major cause of death and illness in industrialised countries. Like other hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, pravastatin reduces total and low density lipoprotein (LDL)-cholesterol levels and increases high density lipoprotein (HDL)-cholesterol levels. Cholesterol modification with pravastatin in middle-aged hypercholesterolaemic men without CHD (i.e. primary prevention) was shown in the West of Scotland Coronary Prevention Study (WOSCOPS) to reduce the incidence of fatal and nonfatal coronary events. In several other large studies, pravastatin reduced the incidence of CHD events in patients with prior CHD (secondary prevention). Large, long term studies of the relationship between cholesterol modification and CHD event rate have been conducted for some, but not all, other HMG-CoA reductase inhibitors. A UK pharmacoeconomic analysis of the WOSCOPS data indicated that primary prevention with pravastatin was associated with a cost of 20,375 Pounds per year of life gained (YLG) [discounted]. Treatment of men at high risk for CHD resulted in a lower cost estimate (13,995 Pounds/YLG). A US economic analysis based on secondary prevention with pravastatin in large plaque regression studies suggested a net cost of drug therapy of $US7124 to $US12,665 per YLG. A number of projected-risk models have attempted to calculate the cost effectiveness of primary or secondary prevention with pravastatin compared with other lipid-modifying interventions. These comparisons indicated that pravastatin was economically superior to intensive lifestyle counselling without drug therapy. Pravastatin generally appeared to be less cost effective than other HMG-CoA reductase inhibitors, although the relative effectiveness of the various drugs depended on the model considered. Risk-projection economic models are subject to methodological limitations, principally the necessity of estimating clinical effectiveness from epidemiological data (often derived from the Framingham Heart Study). An increased absolute risk of CHD improves the cost effectiveness of lipid-lowering therapy. Thus, the cost per YLG of pravastatin in secondary prevention is, in general, lower than that of primary prevention, reflecting the higher absolute risk of second versus first CHD events. However, it is important to note that individual absolute risk rates may overlap between patients receiving primary and secondary prevention. Similarly, treatment of selected individual patients at high risk for CHD events is associated with a lower cost per YLG than unselected treatment. CONCLUSION: In large clinical studies, pravastatin effectively reduced the risk of primary and secondary CHD events. These benefits come at a substantial economic cost, but one that is in line with accepted costs for other medical interventions. Selective treatment of patients or populations at high risk of CHD events improves the cost effectiveness of pravastatin therapy.

Anticholesteremic Agents↗
PubMedDate not supplied

The developmental 'risk factor' model of schizophrenia.

There is no single cause for schizophrenia. We believe that, as with other common chronic diseases such as diabetes and coronary artery disease, the appropriate aetiological model is one involving multiple genes and environmental risk factors; the latter can be divided into (a) predisposing and (b) precipitating. Our model is that genetic and/or early environmental factors cause the development of anomalous neural networks. We postulate that these interact in the growing child with inherited schizotypal traits to establish a trajectory towards an increasingly solitary and deviant life style. This ultimately projects the individual across the threshold for expression of schizophrenia, sometimes by causing the drug abuse and social adversity that appear to precipitate the psychosis.

Environment↗
PubMed1989

Modelling the risk of adult T-cell leukemia/lymphoma in persons infected with human T-lymphotropic virus type I.

Adult T-cell leukemia/lymphoma (ATL), a malignancy of mature CD4-positive lymphocytes, has been etiologically linked to the human retrovirus HTLV-I. Although a long latent period is suggested from migrant studies, little prospective information on the risk of developing ATL among persons with HTLV-I infection is available. We present here a model for ATL risk based upon age- and sex-specific HTLV-I seroprevalence data from a cross-sectional survey of 13,000 Jamaicans and ATL incidence data from a 2 1/2-year case-control study. By examining the age-specific incidence of ATL relative to both adult and childhood-acquired seropositivity versus childhood-acquired seropositivity alone, we provide evidence in support of the hypothesis that childhood infection with HTLV-I is important to the development of ATL. Using this model, the cumulative lifetime risk of ATL for those infected before age 20 is estimated to be 4.0% for males and 4.2% for females. Under this hypothesis, HTLV-I-associated diseases with shorter latent periods, such as tropical spastic paraparesis, should have a higher incidence in adult females than in adult males.

Adolescent↗
PubMed2004

The graft-versus-leukaemia effect after allogeneic bone-marrow transplantation: assessment through competing risks approaches.

In failure time studies involving a chronic disease such as cancer, data often focus on one or more non-fatal events, in addition to survival, to describe the course of the disease. In the example of allogeneic bone marrow transplantation in leukaemic patients, acute graft-versus host disease (aGvHD), relapse and death were taken as the reported events, and we focused on testing the existence of graft-versus-leukaemia (GvL) effect, i.e. that the occurrence of aGvHD modifies the probability of relapse. One of the weaknesses of the standard competing risks models is their inability to model secondary relapses. We thus derived, from two competing risks models, two estimators of cumulative incidence functions of primary and secondary relapses, as well as statistics to test the GvL effect. The approach is illustrated by application to a data set from a cohort of 442 children with acute leukaemia who received an unrelated transplant.

Bone Marrow Transplantation↗
PubMed1998

[Models of preoperative risk stratification in cardiac surgery: the prediction of mortality or of survival?].

BACKGROUND: The need to assess the quality of heart surgery outcomes stimulated the development of pre-surgical risk stratification models in order to predict outcome on the basis of patient characteristics. The aim of the study was to compare the predictive accuracy of hospital mortality according to the following three models: Parsonnet (NBI Score), Higgins (CCF Score) and Roques (French Score), in a setting totally independent from the one in which the models were derived. METHODS: For each of the 516 patients undergoing heart surgery at our institution between January 1992 and December 1993, we calculated the pre-surgical risk according to the three models. Then we compared the predicted mortality against the observed mortality by means of the Shannon accuracy index, the ROC curve analysis and the overestimation histogram. RESULTS: Overall observed mortality (1.5%) was similar to the predicted mortality by the NBI Score (1.5 +/- 2.1%, p = ns), the CCF Score (1.7 +/- 2.0%, p = ns) and the French Score (1.9 +/- 2.5%, p = ns). The predictive accuracy of global mortality is very high and equal with the three models, and it is very low in the 8 patients who died (NBI Score = 0.06 +/- 0.06; CCF Score = 0.125 +/- 0.067; French Score = 0.102 +/- 0.07, p = ns). The area under the ROC curve is identical in the 3 models. CONCLUSIONS: The predicted mortality obtained by the three models is not significantly different from the observed mortality and therefore, the global accuracy is similar and very high, while it is very low for patients who will die. The models for pre-surgical risk stratification are useful for comparing the results among different institutions or different surgeons, or for monitoring the results over time in the same institution, but they cannot be used to accurately predict the individual risk of hospital mortality.

Aged↗
PubMed2001

In vitro human tissue models in risk assessment: report of a consensus-building workshop.

Advances in the technology of human cell and tissue culture and the increasing availability of human tissue for laboratory studies have led to the increased use of in vitro human tissue models in toxicology and pharmacodynamics studies and in quantitative modeling of metabolism, pharmacokinetic behavior, and transport. In recognition of the potential importance of such models in toxicological risk assessment, the Society of Toxicology sponsored a workshop to evaluate the current status of human cell and tissue models and to develop consensus recommendations on the use of such models to improve the scientific basis of risk assessment. This report summarizes the evaluation by invited experts and workshop attendees of the current status of such models for prediction of human metabolism and identification of drug-drug interactions, prediction of human toxicities, and quantitative modeling of pharmacokinetic and pharmaco-toxicodynamic behavior. Consensus recommendations for the application and improvement of current models are presented.

Cell Culture Techniques↗
PubMed2003

Modeling risk-adjusted capitation rates for Umbria, Italy.

We studied the potential effect of refining per capita financing in Italy by risk adjustment using severity of illness as well as age and gender. Data were drawn from hospital, pharmaceutical, and demographic files for the entire population of the Umbrian region of Italy in 1997 and 1998. Hospitalization data from 1997 were used to classify patients into severity of illness categories which were hypothesized to be at risk for higher health services costs in 1998. Data on costs in 1998 were developed from hospital and pharmaceutical administrative data. Coefficients from 1997 models were used to develop predicted 1998 costs. Predicted costs in 1998 were compared to observed costs. Disease Staging models identified 155 unique clinical risk adjustment categories. These categories included 5.3% of the Umbrian population in 1997, who accounted for 21.6% of costs in the next year. In prediction models of future year costs using Umbrian data, R(2) values for Disease Staging models were 0.16, compared to values of 0.07 for a risk adjustment model used by Medicare. By identifying groups within the overall population who were more severely ill and who used more resources, these models can be used to assist health care planners estimate health care resources such as facilities, manpower, and programs.

Journal Article↗
PubMed1997

Predictors of survival in HIV-infected persons with 50 or fewer CD4 cells/mm3.

The objective of this study was to identify prognostic factors for survival in patients with pretreatment CD4 < or =50 cells/mm3 treated with nucleoside analogs, and to develop and validate a mortality risk model based on these factors. The design of the study consisted of retrospective analysis of AIDS Clinical Trials Group (ACTG) protocols 116a, 116b/117, 155, and 118. The setting was the multicenter AIDS Clinical Trials Group. The patients were HIV-infected with pretreatment CD4 < or =50 cells/mm3 and various degrees of prior zidovudine (ZDV) use. Double-blind, three-arm randomized control trials ACTG 116a and ACTG 116b/117 compared ZDV with didanosine (ddI). ACTG 155 compared ZDV with zalcitabine or combination therapy. Our validation study, ACTG 118, compared the effects of three different doses of ddI on survival. The main outcome measures were survival and mortality. The three studies combined enrolled 699 patients with entry CD4 T-lymphocyte counts of < or =50 cells/mm3. Forty percent of patients died during follow-up, with a median survival of 19.7 months. Multivariate analysis showed shorter survival at p < 0.0001 with lower CD4 count (relative hazard [RH] = 0.98) and lower hemoglobin level (RH = 0.81). Other factors included older age (RH = 1.03), male gender (RH = 1.70), Hispanic ethnicity (RH = 1.68), and symptomatic disease stage (RH = 2.06). Our predictive mortality risk model differentiated well patients with differing risks of mortality. When the risk model was applied to ACTG 118, the validation data set, the identified prognostic factors could distinguish patients with varying risks of death (p < 0.001, stratified log-rank test). These results demonstrate that CD4 T-lymphocytes counts < or =50 cells/mm3 should not be considered a precursor of imminent death; considerable variability in survival exists in severely immunocompromised patients. Our identification of prognostic indicators for survival can aid clinicians and patients in management of their disease and researchers in design of future clinical trials.

Adolescent↗
PubMed1981

Structural differences in pericentric inversions. Application to a model of risk of recombinants.

The potential chromosomal imbalance in offspring of pericentric inversion heterozygotes can be evaluated by measuring (% of haploid autosomal length, % HAL) the chromosomal segments distal to the breakpoints in the inversion. These distal segments were measured in presently reported and published cases of pericentric inversions, divided into two ascertainment groups: (I) those ascertained through recombinant offspring and (II) those ascertained through balanced heterozygotes. The distal segments in group II inversions were significantly larger than those of group I, i.e., the potentially larger chromosomal imbalances were not observed in full-term offspring. These results are discussed in relation to the model of risk of abnormal offspring in the progeny of heterozygotes for structural rearrangements (the chromosome imbalance size--viability model). The mean distal segment sizes for group I and group II pericentric inversions were respectively not significantly different from the mean interchange segment size for a sample of reciprocal translocations divided into the same two ascertainment groups. It was concluded that the restrictions on the size (% HAL) of chromosomal imbalance in offspring surviving until term are similar whether this imbalance arises from reciprocal translocations or pericentric inversions.

Chromosome Aberrations↗
PubMed1994

Psychosocial, behavioral, and medical outcomes in children with epilepsy: a developmental risk factor model using longitudinal data.

OBJECTIVE: We studied factors predicting the risk of adverse long-term psychosocial, behavioral, and medical outcomes in children with epilepsy. METHODS: Children (N = 157, 4.5 to 13 years) were enrolled in a prospective longitudinal study when first seen. Potential subjects were excluded if they were moderately or severely mentally retarded, had motor or sensory handicaps interfering with testing, or did not speak either English or Spanish. MEASURES: To develop risk predictors, we collected information regarding the child's medical and seizure history, cognitive functioning, and behavior problems, and family functioning. Children and their families were followed for a minimum of 18 months, then underwent reassessment of medical status, parent's attitudes toward epilepsy, and the child's behavioral and cognitive functioning. Data were analyzed by confirmatory factor analysis to develop baseline factors (Sociocultural Risk, Seizure Risk, and Behavior Problems) and outcome factors (Medical/Seizure Problems, Parent's Negative Attitudes Toward Epilepsy, and Behavior Problems), followed by structural equation modeling to determine across-time causal effects. Eighty-eight subjects completed all baseline and outcome measures. RESULTS: Among significant across-time effects, Medical Outcome was predicted by Seizure Risk. An increased number of stressful life events predicted better Medical Outcome. Low acculturation increased Parent's Negative Attitudes and was associated with increased Behavior Problems at baseline. Behavior Problems were stable across time. It is interesting that IQ did not affect any of the outcomes, although its effect may have been mediated through other baseline measures. CONCLUSIONS: Seizure history was the best predictor of ongoing medical difficulties, whereas the most important causes of ongoing parental anxiety and negative attitudes toward epilepsy were sociocultural. Variation in medical or attitudinal outcomes was not influenced by either the child's IQ or reported behavioral problems. These findings suggest that to alter attitudes toward epilepsy, programs should be tailored to the sociocultural background of the family. Studies of quality of life of children with epilepsy should include appropriate sociocultural measures.

Acculturation↗
PubMed1996

Creating an integrated health care system: the health and human risk management model.

This article critiques the current health care system and presents a new conceptual model that offers the potential for an integrated health care system in the future. Health care currently consists of parallel care systems based on the competing conceptual frameworks of the medical model and the psychosocial model. It is argued that psychosocial factors must be included in an integrated system. Research literature is reviewed that documents the need for, the therapeutic effectiveness of, and the medical cost-offset benefits of mental and behavioral health interventions. The Health and Human Risk Management Model is described and illustrated with a case example as well as research outcomes from its implementation at United HealthCare Corporation.

Delivery of Health Care, Integrated↗
PubMed2004

MORM--a Petri net based model for assessing OH&S risks in industrial processes: modeling qualitative aspects.

Because of the increase in workplace automation and the diversification of industrial processes, workplaces have become more and more complex. The classical approaches used to address workplace hazard concerns, such as checklists or sequence models, are, therefore, of limited use in such complex systems. Moreover, because of the multifaceted nature of workplaces, the use of single-oriented methods, such as AEA (man oriented), FMEA (system oriented), or HAZOP (process oriented), is not satisfactory. The use of a dynamic modeling approach in order to allow multiple-oriented analyses may constitute an alternative to overcome this limitation. The qualitative modeling aspects of the MORM (man-machine occupational risk modeling) model are discussed in this article. The model, realized on an object-oriented Petri net tool (CO-OPN), has been developed to simulate and analyze industrial processes in an OH&S perspective. The industrial process is modeled as a set of interconnected subnets (state spaces), which describe its constitutive machines. Process-related factors are introduced, in an explicit way, through machine interconnections and flow properties. While man-machine interactions are modeled as triggering events for the state spaces of the machines, the CREAM cognitive behavior model is used in order to establish the relevant triggering events. In the CO-OPN formalism, the model is expressed as a set of interconnected CO-OPN objects defined over data types expressing the measure attached to the flow of entities transiting through the machines. Constraints on the measures assigned to these entities are used to determine the state changes in each machine. Interconnecting machines implies the composition of such flow and consequently the interconnection of the measure constraints. This is reflected by the construction of constraint enrichment hierarchies, which can be used for simulation and analysis optimization in a clear mathematical framework. The use of Petri nets to perform multiple-oriented analysis opens perspectives in the field of industrial risk management. It may significantly reduce the duration of the assessment process. But, most of all, it opens perspectives in the field of risk comparisons and integrated risk management. Moreover, because of the generic nature of the model and tool used, the same concepts and patterns may be used to model a wide range of systems and application fields.

Journal Article↗
PubMedDate not supplied

Re-examination of the ED01 study. Review of statistics: the need for realistic statistical models for risk assessment.

The statistical analyses of the ED01 study leave us with the following conclusions: 1) To be realistic, risk assessment using chronic animal studies should be based on time-to-response data and models. 2) Simple standards such as a virtual safe dose and simple models such as the one-hit model or linear extrapolation seem ill-suited as scientific means for risk assessment for such extensive data sets as the ED01 study. 3) The development of new methods for analysis, modeling and risk assessment should be encouraged if future decisions are to be realistically based on chronic animal studies.

2-Acetylaminofluorene↗