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PubMed2002

Cholesterol control, medication adherence and illness cognition.

OBJECTIVE: To examine the relation between illness cognitions and two measures of adherence in patients with hypercholesterolaemia, a disease marked by chronically high cholesterol. DESIGN: Cross-sectional. Based on the self-regulation model (Leventhal, Diefenbach, & Leventhal, 1992), patients' illness cognitions were predicted to be related to cholesterol control and medication adherence. Patients with illness cognitions consonant with an experts' mental model of hypercholesterolaemia were expected to show better control and adherence. METHOD: Hypercholesterolaemic patients (N = 169) were recruited at a university-based general medicine clinic. Patients completed a survey that assessed beliefs about hypercholesterolaemia and medication-taking behaviour. Cholesterol levels were obtained from patients' medical charts. RESULTS: Low-density lipoprotein (LDL) cholesterol control was related to believing that hypercholesterolaemia is a stable, asymptomatic disease with severe coronary consequences, and self-report of medication adherence was related to believing that the disease has severe coronary consequences (ps <.05). LDL cholesterol differences between groups low and high in various illness beliefs ranged between 0.04 and 0.24 mmol/l (2 and 9 mg/dl) which translated to between 1% and 18% lower LDL cholesterol levels. CONCLUSION: The present study shows several relations that have not been previously demonstrated between better LDL cholesterol control and illness cognition, cognitions that were similar to an expert or physician's mental model of hypercholesterolaemia. The magnitude of differences in patient cholesterol levels was small but may be clinically important.

Journal Article↗

PubMed2003

A new mathematical model based on clinical and laboratory variables for the diagnosis of Sjögren's syndrome.

Sjögren's syndrome (SS) is a systemic autoimmune disease that mainly affects exocrine glands. A diagnosis of SS in its early stages has a potential clinical relevance, but it is difficult and cannot be made solely on clinical grounds. Several sets of diagnostic criteria have been proposed, but none has met with a general consensus. Minor salivary gland has been judged to be the "gold standard" for the diagnosis of SS. However, it is a painful procedure and has a small but significant proportion of both false positive and false negative results. The aim of our study was to develop a simple mathematical score that uses clinical and laboratory variables for diagnosing SS, thereby reducing the need of minor salivary gland. The following variables were included in the model: ANA, SS-A/SS-B, Schirmer's Test/BUT, C3/C4, serum gammaglobulin levels. One hundred consecutive individuals reporting clinical syndromes consistent with a sicca syndrome were included in the study. The application of our multifactorial mathematical model has shown a high predictive value for SS vs controls or vs patients with other autoimmune disorders (Sensitivity 93%, Specificity 100%), with an estimated minor salivary gland reduction of 77%. We conclude that our mathematical model can be considered a useful non-invasive approach for diagnosing Sjogren's Syndrome and recommend its validation on a larger scale.

Adult↗

PubMed2005

Acute knee trauma: value of a short dedicated extremity MR imaging examination for prediction of subsequent treatment.

PURPOSE: To assess the predictive value of a short magnetic resonance (MR) imaging examination, in addition to or instead of radiography, performed in patients with acute knee trauma to identify those who require additional treatment versus those who do not and can be discharged without further follow-up. MATERIALS AND METHODS: The randomized controlled trial and use of collected data for prediction modeling were approved by the institutional review board; informed consent was obtained. Patients with recent knee injury were included in the trial if radiography was ordered. They were randomized into a group undergoing only radiography and a group undergoing radiography plus immediate MR imaging. A 0.2-T dedicated extremity MR imager and four short pulse sequences were used. Univariable and multivariable logistic regression analysis was used to evaluate patient characteristics, trauma mechanism, and findings at radiography and MR imaging for their value in prediction of need for subsequent treatment within the 6-month follow-up. RESULTS: Data in 189 patients (123 male patients, 66 female patients; mean age, 33.4 years), 109 of whom underwent treatment after their initial visit, were analyzed. Age of 30 years or older, indirect trauma mechanism, radiographic results, and MR imaging results were significant predictors of need for treatment in univariable and multivariable analyses (P < .05). In the multivariable analysis, only abnormal MR imaging results were significantly predictive of need for treatment, and only when MR imaging replaced radiography (odds ratio, 2.61; 95% confidence interval: 1.12, 6.06). CONCLUSION: Implementation of a dedicated extremity MR imaging examination, in addition to or instead of radiography, performed in patients with traumatic knee injury improves prediction of the need for additional treatment but does not significantly aid in identification of patients who can be discharged without further follow-up. Value of a short MR imaging examination in the initial stage after knee trauma is limited.

Adult↗

PubMed1990

Prospective evaluation of onchocerciasis control strategies.

After more than 13 years of aerial larviciding, the Onchocerciasis Control Programme in West-Africa (OCP) is considering the future of its control activities. In the original OCP-area the prevalence of infection has been brought down to very low levels and cessation of larviciding is being contemplated. The introduction of ivermectin has broadened the spectrum of available control measures. Countries outside the OCP are also planning chemotherapy-based onchocerciasis control. The prediction of the epidemiological impact of the different control options is difficult in view of the many factors which affect the dynamics of a chronic infectious disease like onchocerciasis. We developed the computer simulation model ONCHOSIM, which takes these many factors and their interrelationships into account. The program has a broad spectrum of uses of which some examples are given. It is explained how the model is used to simulate endemic situations and epidemiological trends during vector control. These trends can be explained in terms of longevity of the parasite and other model parameters. Secondly, predictions are made about the risk of recrudescence after stopping larviciding. Finally, the possible role of ivermectin to control recrudescence after interruption of vector control and to reduce disease symptoms in an endemic situation is explored. The latter application is also important outside the OCP-area. This shows the usefulness of ONCHOSIM as a means for transferring the OCP-knowledge about onchocerciasis control to other countries. From our experience with ONCHOSIM, it is concluded that model based prospective evaluation of control measures is useful in synthesizing existing knowledge, in steering applied research, in interpreting the results of experimental studies, and last but not least, in aiding the policy-making process.

Africa, Western↗

PubMed2005

A hierarchical perspective of plant diversity.

Predictive models of plant diversity have typically focused on either a landscape's capacity for richness (equilibrium models), or on the processes that regulate competitive exclusion, and thus allow species to coexist (nonequilibrium models). Here, we review the concepts and purposes of a hierarchical, multiscale model of the controls of plant diversity that incorporates the equilibrium model of climatic favorability at macroscales, nonequilibrium models of competition at microscales, and a mixed model emphasizing environmental heterogeneity at mesoscales. We evaluate the conceptual model using published data from three spatially nested datasets: (1) a macroscale analysis of ecoregions in the continental and western U.S.; (2) a mesoscale study in California; and (3) a microscale study in the Siskiyou Mountains of Oregon and California. At the macroscale (areas from 3889 km2 to 638,300 km2), climate (actual evaporation) was a strong predictor of tree diversity (R2 = 0.80), as predicted by the conceptual model, but area was a better predictor for vascular plant diversity overall (R2 = 0.38), which suggests different types of plants differ in their sensitivity to climatic controls. At mesoscales (areas from 1111 km2 to 15,833 km2), climate was still an important predictor of richness (R2 = 0.52), but, as expected, topographic heterogeneity explained an important share of the variance (R2 = 0.19) showed positive correlations with diversity of trees, shrubs, and annual and perennial herbs, and was the primary predictor of shrub and annual plant species richness. At microscales (0.1 ha plots), spatial patterns of diversity showed a clear unimodal pattern along a climate-driven productivity gradient and a negative relationship with soil fertility. The strong decline in understory and total diversity at the most productive sites suggests that competitive controls, as predicted, can override climatic controls at this scale. We conclude that this hierarchical, multiscale model provides a sound basis to understand and analyze plant species diversity. Specifically, future research should employ the principles in this paper to explore climatic controls on species richness of different life forms, better quantify environmental heterogeneity in landscapes, and analyze how these large-scale factors interact with local nonequilibrium dynamics to maintain plant diversity.

Biodiversity↗

PubMed2000

Use of artificial neural networks to predict drug dissolution profiles and evaluation of network performance using similarity factor.

PURPOSE: To use artificial neural networks for predicting dissolution profiles of matrix-controlled release theophylline pellet preparation, and to evaluate the network performance by comparing the predicted dissolution profiles with those obtained from physical experiments using similarity factor. METHODS: The Multi-Layered Perceptron (MLP) neural network was used to predict the dissolution profiles of theophylline pellets containing different ratios of microcrystalline cellulose (MCC) and glyceryl monostearate (GMS). The concepts of leave-one-out as well as a time-point by time-point estimation basis were used to predict the rate of drug release for each matrix ratio. All the data were used for training, except for one set which was selected to compare with the predicted output. The closeness between the predicted and the reference dissolution profiles was investigated using similarity factor (f2). RESULTS: The f2 values were all above 60, indicating that the predicted dissolution profiles were closely similar to the dissolution profiles obtained from physical experiments. CONCLUSION: The MLP network could be used as a model for predicting the dissolution profiles of matrix-controlled release theophylline pellet preparation in product development.

Cellulose↗

PubMed1998

The cerebellum, predictive control and motor coordination.

I argue that the cerebellum has at least two related roles, both sub-served by its operation as a 'forward model' of the motor system. First, it provides an internal state estimate or sensory prediction that is used for online control of movements; second, these predictive state estimates are used to coordinate actions by different effectors in the normal coordination of eye and hand, reach and grasp, etc. Preliminary electrophysiological data from cerebellar cortical neurons in the monkey supports the hypothesis that a proportion of cells code for the sensory consequences of movement. In a contrast between normal visually guided movement of a cursor and mirror reversed movement, approximately half the sample of 47 directionally sensitive cells were found to code for the movement of the cursor controlled by the monkey's limb, and not the limb movement itself. Functional imaging of the human cerebellum further supports the hypothesis that the cerebellum is involved in motor coordination. Subjects were tested performing ocular tracking, manual tracking without eye movement, or combined eye and hand tracking. Activation of cerebellar areas related to movement of eyes or hand alone was significantly enhanced when the subjects performed coordinated eye and hand tracking of a visual target.

Animals↗

PubMed2001

Active noise control in a free field with virtual sensors.

The zone of local control around a "virtual energy density sensor" is compared with that offered by an actual energy density sensor, a single microphone, and a virtual microphone. Intended as an introduction to the concept of forward difference prediction and a precursor to evaluating the virtual sensor control algorithms in damped enclosures, this paper investigates an idealized scenario of a single primary sound source in a free-field environment. An analytical model is used to predict the performance of the virtual error sensors and compare their control performance with their physical counterparts. The model is then experimentally validated. The model shows that in general the virtual energy density sensor outperforms the actual energy density sensor, the actual microphone, and the virtual microphone in terms of centering a practically sized zone of local control around an observer who is remotely located from any physical sensors. However, in practice, the virtual sensor algorithms are shown to be sensitive (by varying degrees) to short wavelength spatial pressure variations of the primary and secondary sound fields.

Acoustics↗

PubMed2002

Predictive accuracy of a model of volatile anesthetic uptake.

UNLABELLED: A computer program that models anesthetic uptake and distribution has been in use in our department for 20 yr as a teaching tool. New anesthesia machines that electronically measure fresh gas flow rates and vaporizer settings allowed us to assess the performance of this model during clinical anesthesia. Gas flow, vaporizer settings, and end-tidal concentrations were collected from the anesthesia machine (Datex S/5 ADU) at 10-s intervals during 30 elective anesthetics. These were entered into the uptake model. Expired anesthetic vapor concentrations were calculated and compared with actual values as measured by the patient monitor (Datex AS/3). Sevoflurane was used in 16 patients and isoflurane in 14 patients. For all patients, the median performance error was -0.24%, the median absolute performance error was 13.7%, divergence was 2.3%/h, and wobble was 3.1%. There was no significant difference between sevoflurane and isoflurane. This model predicted expired concentrations well in these patients. These results are similar to those seen when comparing calculated and actual propofol concentrations in propofol infusion systems and meet published guidelines for the accuracy of models used in target-controlled anesthesia systems. This model may be useful for predicting responses to changes in fresh gas and vapor settings. IMPLICATIONS: We compared measured inhaled anesthetic concentrations with those predicted by a model. The method used for comparison has been used to study models of propofol administration. Our model predicts expired isoflurane and sevoflurane concentrations at least as well as common propofol models predict arterial propofol concentrations.

Adolescent↗

PubMed2006

Narcissism and childhood recollections: a quantitative test of psychoanalytic predictions.

Different psychotherapeutic theories provide contradictory accounts of adult narcissism as the product of either parental coldness or excessive parental admiration during childhood. Yet, none of these theories has been tested systematically in a nonclinical sample. The authors compared four structural equation models predicting overt and covert narcissism among 120 United Kingdom adults. Both forms of narcissism were predicted by both recollections of parental coldness and recollections of excessive parental admiration. Moreover, a suppression relationship was detected between these predictors: The effects of each were stronger when modeled together than separately. These effects were found after controlling for working models of attachment; covert narcissism was predicted also by attachment anxiety. This combination of childhood experiences may help to explain the paradoxical combination of grandiosity and fragility in adult narcissism.

Adolescent↗

PubMed1992

Staff attitudes towards patients: the influence of causal attributions for illness.

The aim of this study is to determine whether staff attitudes towards patients are affected by staff causal attributions. Forty-eight nurses and doctors were presented with five case histories of patients suffering from lung cancer, liver cirrhosis myocardial infarction, breast lump and cervical cancer. There were two versions of each case: one patient had followed and the other had ignored a relevant health action (e.g. not smoking in the lung cancer patients). Subjects responded to just one version of each case. For all five conditions, staff had significantly more negative attitudes towards patients who had not undertaken a relevant health behaviour compared with patients who had undertaken a relevant health behaviour. A second group of nurses rated it as more likely that this latter group of patients could have prevented their illnesses. The results suggest that information about a patient's health habits prior to illness influence staff attitudes to that patient. Evidence is presented suggesting that the effect of this information is mediated by perceived controllability of the illness, as predicted by an attributional model of helping behaviour.

Attitude of Health Personnel↗

PubMed2006

A randomised controlled trial evaluating the effects of two workstation interventions on upper body pain and incident musculoskeletal disorders among computer operators.

BACKGROUND: Call centre work with computers is associated with increased rates of upper body pain and musculoskeletal disorders. METHODS: This one year, randomised controlled intervention trial evaluated the effects of a wide forearm support surface and a trackball on upper body pain severity and incident musculoskeletal disorders among 182 call centre operators at a large healthcare company. Participants were randomised to receive (1) ergonomics training only, (2) training plus a trackball, (3) training plus a forearm support, or (4) training plus a trackball and forearm support. Outcome measures were weekly pain severity scores and diagnosis of incident musculoskeletal disorder in the upper extremities or the neck/shoulder region based on physical examination performed by a physician blinded to intervention. Analyses using Cox proportional hazard models and linear regression models adjusted for demographic factors, baseline pain levels, and psychosocial job factors. RESULTS: Post-intervention, 63 participants were diagnosed with one or more incident musculoskeletal disorders. Hazard rate ratios showed a protective effect of the armboard for neck/shoulder disorders (HR = 0.49, 95% CI 0.24 to 0.97) after adjusting for baseline pain levels and demographic and psychosocial factors. The armboard also significantly reduced neck/shoulder pain (p = 0.01) and right upper extremity pain (p = 0.002) in comparison to the control group. A return-on-investment model predicted a full return of armboard and installation costs within 10.6 months. CONCLUSION: Providing a large forearm support combined with ergonomic training is an effective intervention to prevent upper body musculoskeletal disorders and reduce upper body pain associated with computer work among call centre employees.

Adult↗

PubMed1983

Evaluation of "in feed" vaccination of piglets and sows against enteropathogenic "E. coli" using environmental production parameters.

Current approaches to the immunological control of enteric E. coli infections in pig herds concentrate on the provision of passive immunity for the neonate by multiple parenteral vaccination of the sow to stimulate colostral antibody production. Little account is taken of the kinetics of the animals' natural immune response. In particular the potential of the gut as a target organ for immunization has largely been ignored in practical disease control. A new approach to the problem, which combines oral with parenteral vaccination, stimulates a colostral antibody response closely mimicking a sow's natural response to infections and comparison between this and classical parenteral vaccination, using an acute E. coli infection model, demonstrated the greater protective efficacy conferred by the new protocol. The widespread use of this method of vaccination has been continuously monitored, using production parameters most relevant to the farming industry. From this evaluation of user experience and results of trials conducted in various locations, a new perspective is emerging which indicates the vaccine has a wider spectrum of biological activity than was expected. Production, health and environmental benefits are arising which could not have been predicted from a model merely concerned with the control of alimentary E. coli infection.

Age Factors↗

PubMed2004

Optimality principles in sensorimotor control.

The sensorimotor system is a product of evolution, development, learning and adaptation-which work on different time scales to improve behavioral performance. Consequently, many theories of motor function are based on 'optimal performance': they quantify task goals as cost functions, and apply the sophisticated tools of optimal control theory to obtain detailed behavioral predictions. The resulting models, although not without limitations, have explained more empirical phenomena than any other class. Traditional emphasis has been on optimizing desired movement trajectories while ignoring sensory feedback. Recent work has redefined optimality in terms of feedback control laws, and focused on the mechanisms that generate behavior online. This approach has allowed researchers to fit previously unrelated concepts and observations into what may become a unified theoretical framework for interpreting motor function. At the heart of the framework is the relationship between high-level goals, and the real-time sensorimotor control strategies most suitable for accomplishing those goals.

Adaptation, Physiological↗

PubMed1976

Learned helplessness, depression, and the attribution of failure.

Depressed and nondepressed college students received experience with solvable, unsolvable, or no discrimination problems. When later tested on a series of patterned anagrams, depressed groups performed worse than nondepressed groups, and unsolvable groups performed worse than solvable and control groups. As predicted by the learned helplessness model of depression, nondepressed subjects given unsolvable problems showed anagram deficits parallel to those found in naturally occurring depression. When depressed subjects attributed their failure to the difficulty of the problems rather than to their own incompetence, performance improved strikingly. So, failure in itself is apparently not sufficient to produce helplessness deficits in man, but failure that leads to a decreased belief in personal competence is sufficient.

Achievement↗

PubMed2005

[Comparison of multiple prediction models for hypertension (Neural networks, logistic regression and flexible discriminant analyses)].

OBJECTIVE: In this study, we compared performances of logistic regression analysis (LR), flexible discriminant analysis (EAA) and neural networks (SA) in prediction of primary hypertension. METHODS: Predictor variables were family history, lipoprotein A, triglyceride, smoking and body mass index. The data were collected from Cardiology Clinic of Trakya University Medical Faculty in Turkey, 2001. Logistic regression analysis, flexible discriminant analysis and neural networks were used for prediction of control and hypertension groups. Comparison of the performance of all models was done using receiver operating characteristic (ROC) curve analysis. RESULTS: All models had areas under the ROC curve in the range of 0.793-0.984 and SA had sensitivity, specificity, and accuracy greater than 90% at ideal threshold. ROC curve areas of SA and LR, and SA and EAA were statistically different (p<0.001 and p<0.001 respectively), while ROC curve areas of EAA and LR did not differ (p>0.05). CONCLUSION: We concluded that family history, lipoprotein A, triglyceride, smoking and body mass index variables can be used for prediction of control and hypertension groups with statistically better performance of SA over LR and EAA.

Body Mass Index↗

PubMed2001

Comparing apples and oranges--model-based assessment of different tsetse-transmitted trypanosomosis control strategies.

The current control strategies for tsetse-transmitted trypanosomosis in cattle (trypanocidal drugs, tsetse control and trypanotolerant cattle) are briefly reviewed and their adoption rates in different geographic regions of sub-Saharan Africa are presented. The impact of these control strategies and the potential use of vaccines, should they be developed, on trypanosomosis transmission were compared using a mathematical model. The relative trypanosomosis prevalence compared with no control was estimated across a range of control coverages (from none to complete control coverage) by varying the change in specific model parameters influenced by individual control measures. Based on this comparison, the relative rankings of the effect of control strategies on reducing disease prevalence were: vector control, vaccination, and drug use, in that order. In this model, trypanotolerance was assumed to decrease disease prevalence, but not to influence transmission. Differences in the predicted impact of control measures on the transmission of human sleeping sickness are discussed. Finally, the role of transmission model outputs as inputs for economic models to guide investment decisions for trypanosomosis control is emphasised.

Africa South of the Sahara↗

PubMed2001

Risk adjustment alternatives in paying for behavioral health care under Medicaid.

OBJECTIVE: To compare the performance of various risk adjustment models in behavioral health applications such as setting mental health and substance abuse (MH/SA) capitation payments or overall capitation payments for populations including MH/SA users. DATA SOURCES/STUDY DESIGN: The 1991-93 administrative data from the Michigan Medicaid program were used. We compared mean absolute prediction error for several risk adjustment models and simulated the profits and losses that behavioral health care carve outs and integrated health plans would experience under risk adjustment if they enrolled beneficiaries with a history of MH/SA problems. Models included basic demographic adjustment, Adjusted Diagnostic Groups, Hierarchical Condition Categories, and specifications designed for behavioral health. PRINCIPAL FINDINGS: Differences in predictive ability among risk adjustment models were small and generally insignificant. Specifications based on relatively few MH/SA diagnostic categories did as well as or better than models controlling for additional variables such as medical diagnoses at predicting MH/SA expenditures among adults. Simulation analyses revealed that among both adults and minors considerable scope remained for behavioral health care carve outs to make profits or losses after risk adjustment based on differential enrollment of severely ill patients. Similarly, integrated health plans have strong financial incentives to avoid MH/SA users even after adjustment. CONCLUSIONS: Current risk adjustment methodologies do not eliminate the financial incentives for integrated health plans and behavioral health care carve-out plans to avoid high-utilizing patients with psychiatric disorders.

Adult↗