bluuebunny/crossref_metadata_2025 huggingface dataset:
Is craving the source of compulsive drug use?
Authors: Tiffany Stephen T. , Carter Brian L.
Published: March 2007

Compulsive drug use, which is typically portrayed as a defining quality of addictive behavior, has been described as a pattern of drug consumption that is stimulus bound, stereotyped, difficult to regulate and identified by a loss of control over intake. It is widely assumed that compulsive drug use is caused by drug craving. This assumption is supported by numerous findings of a general correspondence between measures of craving and drug-use behavior. A more focussed analysis of the available data, however, reveals that craving and drug use are not coupled to the degree required by the hypothesis that craving is the source of all drug use in the addict. As an alternative to this craving-based view, compulsive drug use could be characterized as a form of automatized behavior. Automatic performance is assumed to develop over the course of repeated practice of motor and cognitive skills. Automatized behavior, like compulsive drug use, tends to be stimulus bound, stereotyped, effortless, difficult to control and regulated largely outside of awareness. The formulation of drug compulsion as a manifestation of automaticity rather than craving allows addiction researchers to apply methods and measures derived from cognitive sciences to investigate the fundamental organization of compulsive drug-use behavior.
A naturalistic study of home detoxification from opiates using lofexidine
Authors: Brown A.S. , Fleming P.M.
Published: March 2007

The study describes the outcome of home detoxification from opiates using lofexidine, a centrally-acting α 2 adrenergic agonist, in a consecutive series of 28 unselected individuals. Eleven detoxifications (39%) were successful and 17 (61%) unsuccessful. No major medical or psychological problems were reported. Successful outcome was associated with not using heroin, good compliance with a methadone programme and prediction of success by the key worker. Home detoxification using lofexidine appears to be a useful treatment for some opiate-dependent individuals, and is most likely to be successful in those individuals whose drug use is already well-controlled.
The effects of clonidine on the fear-inhibited light reflex
Authors: Bitsios P. , Szabadi E. , Bradshaw C.M.
Published: March 2007

We have shown previously that pupil diameter increases and the amplitude of the pupillary light reflex is reduced when subjects are under threat of an aversive event (electric shock), and that light reflex amplitude correlates negatively with subjective anxiety. Furthermore, we have shown that the threat-induced reduction in light reflex amplitude is sensitive to the effect of the anxiolytic drug diazepam. We have suggested that the 'fear-inhibited light reflex' paradigm could be used as a laboratory model of human anxiety. In the present study, we examined whether a single oral dose (200 μg) of the sedative-sympatholytic drug clonidine would antagonize the effects of threat on the pupillary light reflex. Twelve healthy male volunteers participated in two sessions separated by seven days in which they ingested clonidine 200 mg or placebo in a double-blind, balanced, cross- over design. Light stimuli (0.43 mW/cm2, 200 msec) were generated by a green (peak wavelength 565 nm) light- emitting diode, and pupil diameter was monitored by computerized binocular infrared television pupillometry in the dark. The light reflex response was recorded during either the anticipation of a shock ('threat' blocks) or periods in which no shocks were anticipated ('safe' blocks). The shock was a single square wave current pulse (1.5 mA, 50 msec) applied to the median nerve at the end of the experiment. Following each 'threat' or 'safe' block, subjects rated their anxiety using visual analogue scales. Two-factor ANOVA (treatment x condition) showed that clonidine treatment antagonized both the threat-induced increase in pupil diameter and the threat- induced reduction in light reflex amplitude. These effects, however, were not threat-specific since clonidine also reduced pupil diameter and enhanced light reflex amplitude in the 'safe' condition. Clonidine also reduced subjective alertness but not subjective anxiety in the 'threat' condition. These findings suggest that the mutual antagonism between clonidine and threat is likely to reflect the opposite effects of the two variables on the central noradrenergic control of pupillary functions, rather than a specific anxiolytic effect.
SSRI-Induced extrapyramidal side-effects and akathisia: implications for treatment
Authors: Lane Roger M.
Published: March 2007

The selective serotonin reuptake inhibitors (SSRIs) may occasionally induce extrapyramidal side-effects (EPS) and/or akathisia.This maybe a consequence of serotonergically-mediated inhibition of the dopaminergic system. Manifestations of these effects in patients may depend on predisposing factors such as the presence of psychomotor disturbance, a previous history of drug-induced akathisia and/or EPS, concurrent antidopaminergic and/or serotonergic therapy, recent monoamine oxidase inhibitor discontinuation, comorbid Parkinson's disease and possibly deficient cytochrome P450 (CYP) isoenzyme status. There is increasing awareness that there may be a distinct form of melancholic or endogenous depression with neurobiological underpinnings similar to those of disorders of the basal ganglia such as Parkinson's disease. Thus, it is not surprising that some individuals with depressive disorders appear to be susceptible to developing drug-induced EPS and/or akathisia. In addition, the propensity for the SSRIs to induce these effects in individual patients may vary within the drug class depending, for example, on their selectivity for serotonin relative to other monoamines, affinity for the 5-HT2C receptor, pharmacokinetic drug interaction potential with concomitantly administered neuroleptics and potential for accumulation due to a long half-life. The relative risk of EPS and akathisia associated with SSRIs have yet to be clearly established. The potential risks may be reduced by avoiding rapid and unnecessary dose titration. Furthermore, early recognition and appropriate management of EPS and/or akathisia is required to prevent the impact of these effects on patient compliance and subjective well-being. It is important that the rare occurrence of EPS in patients receiving SSRIs does not preclude their use in Parkinson's disease where their potentially significant role requires more systematic evaluation.
Dopamine release in the nucleus accumbens and latent inhibition in the rat following microinjections of a 5 -HT1B agonist into the dorsal subiculum: implications for schizophrenia
Authors: Boulenguez P. , Peters S.L. , Mitchell S.N. , Chauveau J. , Gray J.A. , Joseph M.H.
Published: March 2007

Microinjection of a serotonergic 5-HT1B agonist (S-CM-GTNH2, 3μg/l) into the dorsal subiculum (DS) induced long-lasting increases in dopamine (DA; +58%), dihydroxyphenylacetic acid (DOPAC; +15%) and homovanillic acid (HVA; +31%), without changing extracellular levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA), measured by microdialysis in freely moving rats in the shell area of the nucleus accumbens (n. acc). Perfusion of a glutamate-N-methyl-D-aspartate (NMDA) receptor antagonist (MK 801, dizocilpine, 10μM) through the dialysis probe in the n. acc induced similar long-lasting increases in DA and DOPAC, whereas the glutamate-quisqualate/kainate receptor antagonist (CNQX, 50 μM) had no effect. In the presence of dizocilpine in the n. acc, microinjection of S-CM-GTNH2 into the DS could still increase DOPAC and HVA, but DA levels were not further changed, whereas in the presence of CNQX, microinjection of S-CM-GTNH2 into the DS still increased not only DOPAC and HVA, but also DA levels in a way similar to that in the absence of glutamate antagonist. Therefore, activation of 5-HT1B receptors located in the DS increases the release of DA in the n. acc, presumably via the glutamatergic projection to this structure and acting through NMDA receptors in it. This implies either the suppression of a tonic indirect inhibitory influence and/or stimulation of a phasic excitatory effect of glutamate.

Disruption of latent inhibition (LI) has been suggested as a model for a cognitive deficit in schizophrenia (hyperattention to irrelevant stimuli) and is usually associated with an increase in DA release in the n. acc. However, s.c. injection of RU 24 969 (0.5 mg/kg), a mixed 5-HT1A-5-HT1B agonist, which was previously shown to increase DA release in the n. acc, left LI unchanged. Moreover, bilateral microinjections of S-CM-GTNH2 into the rat DS tended to potentiate LI, in spite of the increase in DA in n. acc demonstrated here. It is concluded that not all increases in DA release in the n. acc are functionally equivalent. Sensitization of receptors or impulse- dependent increase in DA release might be necessary to disrupt LI. The possible role of altered serotonergic transmission, through h5-HT1B receptors (human homologue of the rat 5-HT 1B receptors) located in the DS, in acute schizophrenia needs to be further investigated.
Acute and longer-term effects of risperidone in a case of first-episode catatonic schizophrenia
Authors: Kopala Lili C. , Caudle Christopher
Published: March 2007

This case report documents the response of a young, first-episode, neuroleptic naive male with severe catatonic schizophrenia to the novel antipsychotic, risperidone. Initial assessments included the Positive and Negative Syndrome Scales, Global Assessment of Function and the Extrapyramidal Symptom Rating Scale. These were repeated at discharge from hospital and during a 3.5 year outpatient follow-up. Neuroimaging (computed tomography, magnetic resonance imaging and single photon emission tomography) along with electro encephalogram and laboratory examinations were completed. Response to risperidone was prompt, dramatic and sustained over the follow-up period. Possible neurochemical brain mechanisms resulting in catatonia and the role of serotonin/dopamine antagonists such as risperidone are discussed. No other literature on the effect of risperidone in the treatment of severe catatonic schizophrenia in a first-episode patient has been reported.
Neuroleptic discontinuation syndromes
Authors: Tranter Richard , Healy David
Published: March 2007

The existence of discontinuation syndromes following treatment with neuroleptic (antipsychotic) drugs was first outlined in the mid-1960s but the effects of such syndromes have been neglected since then. We have pursued evidence for the existence and nature of discontinuation syndromes following neuroleptics through reports of difficulties following the use of dopamine blocking anti-emetics, the use of chlorpromazine to treat tuberculosis, the use of antidepressant-neuroleptic combinations in affective disorders, the occurrence of tardive syndromes and studies designed to establish the existence of discontinuation syndromes in schizophrenia. Combined these bodies of data point strongly to the existence of discontinuation syndromes after cessation of treatment with neuroleptics which may involve features other than motor dyskinesias. There is at present little evidence on the relative frequency of such syndromes or predisposing factors. The area needs research input to establish the nature of the syndromes that may result, their frequency, predisposing factors and best methods of treatment.
A Dialysis Need-Forecasting Model
Authors: Pliskin Joseph S. , Tell Eileen J.
Published: March 2007

A model to forecast the need for dialysis beds, currently used by the Massachusetts Department of Public Health (DPH), is evaluated after ten years of availability and two years of formal use. The model was originally developed in 1972 to accommo date some informal planning needs of dialysis providers in Massachusetts. In 1978 the model was formally adopted by the DPH for its end stage renal disease planning. The model was designed to be and proved to be flexible in accommodating parameters and inputs specific to a given region, changes due to medical and techno logical innovations, and the acquisition of new data.

This paper evaluates the model in terms of its accuracy, its financial impact, and the impact it has had on the allocation of dialysis resources in Massachusetts. The usefulness of the model as a planning tool is evaluated along several criteria. Two case studies are presented to illustrate how the model has been used to evaluate requests for dialysis facility development or expansion. (Med Decis Making 3:489-500, 1983)
How Physicians Use Clinical Information in Diagnosing Pulmonary Embolism
Authors: Wigton Robert S. , Hoellerich Vincent L. , Patil Kashinath D.
Published: March 2007

To investigate what diagnostic strategies physicians adopt when the literature is unclear about the best use of diagnostic information, the authors examined how physicians weighted eight items of clinical information in diagnosing pulmonary embolism. Thirteen faculty mem bers, 23 house officers, and 19 students estimated the likelihood of pulmonary embolism and predicted whether they would begin treatment in 27 simulated cases. The vignettes were constructed using a fractional factorial design and analyzed using conjoint analysis. Overall the lung scan results (34.7%) and leg examination (19.0%) were weighted most heavily in making the diagnosis, whereas the leg examination (35.7%) was given the greatest weight when deciding about therapy. Weights given by groups at different levels of training were similar, but there was considerable variation within groups. Heterogeneity of diagnostic strategies did not appear to decrease in groups with more training and experience. Multi variate analysis of predictors of pulmonary embolism in 102 actual cases showed that al though lung scan results were important in both actual and simulated cases, heart rate accounted for the most variance in the actual cases but was hardly used in the physicians' strategies. There is considerable variation among physicians in how clinical information is used in diagnosing pulmonary embolism, and the variation may not decrease with increased experience. Key words: conjoint analysis, clinical diagnosis, diagnostic strategies, pulmonary embolism. (Med Decis Making 6:2-11, 1986)
Feasibility of Physician -developed Expert systems
Authors: Tuhrim Stanley , Reggia James A.
Published: March 2007

The authors developed an experimental domain-independent "expert system generator" intended for direct use by physicians. They then undertook a four-year study to determine whether physicians could use such a system effectively. During this period they taught the use of the expert system generator to 70 medical students, who utilized it to build two small medical expert systems. At the conclusion of the course, students were examined on de cision-making concepts and completed anonymous questionnaires. Performance scores, a composite of test and project grades, were calculated for each student. There was no significant association between previous computer experience and performance score. Thirty- two of 47 students responding felt the expert system generator was easy to use; 15 felt it was of moderate difficulty. Forty-three of 47 thought it a useful teaching aid. These data support the conclusion that physicians can learn to use domain-independent software to implement medical expert systems directly, without a knowledge engineer as an intermediary. Key words: expert systems; decision making; diagnostic aids; knowledge engineering; knowl edge base. (Med Decis Making 6:23-26, 1986)
A Decision Theoretic Methodology for Seventy Index Development
Authors: Gustafson David H. , Fryback Dennis G. , Rose Jerry H. , Yick Victor , Prokop Constance T. , Detmer Don E. , Moore Jennifer
Published: March 2007

Severity indices are a key element in evaluation of health programs. But the methodologies used in development of such indices are rarely clearly defined. Moreover, there have been no tests of transportability of the index development methodologies that do exist, so there is no guarantee that panels of physicians convened by different facilitators would produce indices with similar performance characteristics. This paper describes a replicable index development strategy, a heart disease severity index developed by using that methodology, and a test of that methodology's transportability. Key words: severity; utility theory; emer gency medical services; evaluation; multi-attribute utility models. (Med Decis Making 6:27- 35, 1986)
Upper Gastrointestinal Tract Bleeding: Assessing the Diagnostic Contributions of the History and Clinical Findings
Authors: Ohmann Christian , Thon Klaus , Stöltzing Hartmut , Qin Yang  , Lorenz Wilfried
Published: March 2007

Various strategies can be used in the diagnosis of upper gastrointestinal tract bleeding. This study investigates the relevance of anamnestic and clinical findings for the diagnosis of the bleeding source. The authors introduced a computer-aided diagnostic system using Bayes' theorem and compared it with clinicians' predictions using anamnestic and clinical findings only. There was no difference in the overall accuracy rates, but a difference was observed in the diagnostic behaviors of the two "systems." In addition, the discriminatory ability of the computer-aided system, the sharpness of the predictions obtained, and the reliability of the posterior probabilities were analyzed. It is concluded that the clinician and the computer- aided system are not able to discriminate well between the disease categories. Derived classification matrices and probability-based measures show the reasons for the inadequacy of diagnostic information obtainable from the clinical history and physical findings. Key words: computer-aided diagnosis; Bayes' theorem; probabilistic diagnosis; discriminatory ability; reliability; clinical accuracy; upper gastrointestinal tract bleeding. (Med Decis Making 6:208- 215, 1986)
The Effects of Disease Verification and Referral on the Relationship Between Symptoms and Diseases
Authors: Knottnerus J.A.
Published: March 2007

Reference symptoms of individual diseases, which are usually gleaned from hospital-based observations, may not be pertinent to primary health care. Observed relationships between symptoms and diseases can be biased by consultation, disease verification, and referral patterns. These biases are shown to affect sensitivity, specificity, predictive values, the likelihood ratio, and the odds ratio. On the assumption that consultation and disease veri fication rates are positively influenced by symptoms, but not directly by the yet unknown disease status of the patient, the general practitioner will observe a higher sensitivity and a lower specificity than in an unselected population. A positive correlation between symptom and disease will decrease the likelihood ratio, while the predictive values and the odds ratio are not changed after consultation. Referral is influenced by both symptom status and disease verification status. In general, the disease verification and referral patterns of general prac titioners have not been quantified. While the influence of referral cannot easily be corrected for, the likely magnitude and direction of selection bias can be evaluated using simple formulas. A possible way to make unbiased estimations from populations preselected by referral is to compute the predictive values and the odds ratio from the category of patients referred without pre-existing knowledge of the disease status.
Prediction of Fracture in Patients with Acute MusculosKeletal Ankle Trauma
Authors: Diehr Paula , Highley Robert , Dehkordi Farideh , Wood Robert , Krueger Leigh , Teitz Carol , Hermanson Bonnie
Published: March 2007

X-rays taken for ankle trauma contribute significantly to the cost of health care in this country. In an attempt to find clinical correlates of ankle fracture 36 detailed historical and physical examination variables were collected from 587 consecutive patients with ankle trauma, and ankle x-rays were taken of all patients. The association of each variable with the final diagnosis of fracture, rupture, or sprain was tested; 21 variables were significant predictors of fracture (vs. sprain and rupture) and 15 were not significantly associated with final di agnosis. The variables were used in a linear discriminant analysis to develop a rule which would predict the final diagnosis. If only those patients predicted by the rule to have fractures had been x-rayed, all patients with fracture would have been identified but more than a fourth of all ankle trauma patients would have been spared x-rays. This compares favorably with a recently published rule that did not assess sensitivity. A simulated prospective evaluation suggests that these results are stable, but that up to 10% of the fractures could be missed on the first visit. Although current practice is not well documented, it appears that use of this rule could yield substantial cost savings. Key words: linear discriminant analysis; diagnosis; ankle trauma; fractures. (Med Decis Making 8:40-47, 1988)
Sequential Analysis in a Bayesian Model of Diastolic Blood Pressure Measurement
Authors: Schechter Clyde B.
Published: March 2007

A sequential method for diagnosing or excluding hypertension based on the Bayesian model of diastolic blood pressure presented in a companion article is presented. The likelihood ratio method of Wald is modified to include the effects of a prior probability distribution and to constrain the strategy to achieve specified positive and negative predictive values. The resulting formulas for upper and lower limits to diagnose and exclude diastolic hypertension can be evaluated using a hand calculator and a table of areas of the standard normal distribution. The strategy is illustrated for a population having a blood pressure distribution similar to that of the cohort screened for participation in the Hypertension Detection and Follow-up Program, with 90 mm Hg as the cutoff defining hypertension and required positive and negative predictive values of 95%. The performance of the strategy was simulated using Monte Carlo methods. The median number of readings required for diagnosis is three, and 80% of subjects are diagnosed in 11 or fewer readings. In contrast to the strategy's 95% predictive values, a fixed-number-of-measurements strategy requiring the same mean num ber of measurements has a positive predictive value of only 83% and a negative predictive value of 96%. When the parameters of the model have been properly measured or estimated, this method is practical, efficient, and accurate for diagnosing hypertension in a known population. Key words: Bayes' theorem; sequential analysis; hypertension diagnosis. (Med Decis Making 8:191-196, 1988)
Cost-Effectiveness of Screening Strategies for Left Main Coronary Artery Disease in Patients with Stable Angina
Authors: Lee Thomas H. , Fukui Tsuguya , Weinstein Milton C. , Tosteson Anna N.A. , Goldman Lee
Published: March 2007

To define optimal strategies for screening for left main coronary artery disease (LMCAD), the authors evaluated the cost-effectiveness of exercise tolerance testing and cardiac cath eterization in patients with mild stable chest pain, such as patients with definite or probable angina in the Coronary Artery Surgery Study registry (prevalence of LMCAD = 9%). Per formance characteristics of the exercise test, operative mortality, long- term survival rates, and rates of crossing over to surgical therapy for patients initially managed with medical therapy were derived from pooled literature data; cost estimates were based on local charge data. Strategies using the exercise test to identify candidates for catheterization were as sociated with longer life expectancies than either the conservative strategy in which patients would be observed or the more aggressive strategy in which all patients would undergo coronary angiography. The most cost-effective option was to screen patients with an exercise test and to perform catheterization in patients with ≥ 2 mm of ST-segment change. Compared with a strategy of catheterization for ≥ 3 mm of ST-segment change only, this strategy increased life expectancy at marginal costs per year of life saved ranging from $11,263 to $18,100 for 40- to 70-year-old patients, respectively, while, compared with a strategy of observation unless symptoms worsened, its incremental cost-effectiveness was $6,510 to $12,428 per year of life saved. Thus, screening patients with stable chest pain syndromes with exercise tests and performing catheterization for patients with ≥ 2 mm of ST-segment change has cost-effectiveness comparable to that of the treatment of moderate diastolic hypertension. Key words: cost-effectiveness; chest pain; angina; exercise testing; coronary artery surgery; screening. (Med Decis Making 8:268-278, 1988)
Efficient Scheduling of Cystoscopies in Monitoring for Recurrent Bladder Cancer
Authors: Kent Daniel L. , Shachter Ross , Sox Harold C. , Ng Seok Hui  , Shortliffe Linda D. , Moynihan Susan , Torti Frank M.
Published: March 2007

Proper timing for repeated evaluations is difficult to assess. The authors analyzed scheduling of cystoscopy to monitor patients for detection of recurrent bladder cancer assuming that 1) minimizing tumor detection delay helps prevent cancer morbidities; 2) only limited numbers of cystoscopies are available; 3) prediction of recurrence or progression to invasive cancer is uncertain; 4) future tumors recur according to a Poisson process. Assumptions 3 and 4 permit estimation of each patient's recurrence rate. Thus, patients may be compared ac cording to their relative risks of future tumors. With these assumptions, nonlinear optimization theory was used to calculate monitoring schedules for a model practice. Given 5.4 available visits per week per 100 patients, cystoscopy was recommended in 9-11 weeks for high-risk patients and in 30-40 weeks for low-risk patients, depending on stages, grades, and numbers of previous tumors. In contrast, standard cystoscopy was recommended in 13, 26, or 52 weeks, depending only on time elapsed since last recurrence. The calculated schedule implied an average detection delay for potentially invasive tumors of eight weeks, while standard practice led to detection delays of 11 weeks (38% worse). These results suggest that inclusion of each patient's tumor history in an optimization approach may improve follow-up care for patients who have superficial bladder cancers. This approach is being evaluated in a larger clinical setting.
The Analytic Hierarchy Process in Medical Decision Making
Authors: Dolan James G. , Isselhardt Bernard J. , Cappuccio Joseph D.
Published: March 2007

The analytic hierarchy process (AHP) is a quantitative decision making technique created es pecially for complicated, multicriteria decision problems. This report reviews the theoretical foundations of the AHP and shows how to use it in a step-by-step fashion.
A Mathematical Representation of the Expert Panel's Guidelines for Nigh Blood Cholesterol Case-finding and Treatment
Authors: Weissfeld Joel L. , Weissfeld Lisa A. , Holloway James J. , Bernard Annette M.
Published: March 2007

The National Cholesterol Education Program (NCEP) for high blood cholesterol case-finding and treatment recommended discrete treatments according to the results of sequential mea surements of continuous variables (total and low-density lipoprotein cholesterol [LDL-C]). These measurements are subject to intra- and interindividual variability. The authors describe a computer simulation of the NCEP that acknowledges these complexities. The simulation reduces the NCEP into steps, which are represented in a decision tree. The calculation of probabilities at chance nodes takes into account the conditional nature of sequential mea surements of blood cholesterol. The simulation tracks medical resource use and estimates LDL-C reductions within 20 strata, each defining 5% of population distribution for LDL-C. This approach enables a detailed representation of the case-finding process—the sequence of blood cholesterol tests and associated cut-off values that identify individuals needing more intensive evaluation and treatment. Key words: mathematical modeling; screening programs; hypercholesterolemia. (Med Decis Making 1990;10:135-146)
Physicians' Risk Attitudes, Laboratory Usage, and Referral Decisions
Authors: Holtgrave David R. , Lawler Frank , Spann Stephen J.
Published: March 2007

Individual differences in physicians' laboratory use and referral rates are important aspects of practice variation that have real financial and health consequences. A way to explain these differences is needed. In this empirical study, physicians' risk attitudes (measured on a multidimensional scale) are shown to be good predictors of use rates for certain specific laboratory procedures, but not good predictors of physicians' referral rates. A 15-item survey form that measured risk-taking attitudes in the financial, health, social, and ethical domains was administered to all clinical faculty at an academic family practice center ( n = 14). Each physician's utilization rates for the 17 most frequently ordered laboratory procedures were calculated for all patient visits for one calendar year. Overall referral rates were calculated for the same period. Physicians' risk attitudes (12 completed the survey) accounted for over 50% of the variance for several of the laboratory procedures. For example, the rank-order correlation between the complete blood count utilization rate and a Likert-scale item meas uring physicians' propensity to take physical risks was 0.91 (p < 0.001). The details of these findings help to explain an important component of practice variation.
Modeling Time in Medical Decision-support Programs
Authors: Kahn Michael G.
Published: March 2007

To derive meaningful conclusions in a changing medical setting, medical decision-support systems must represent and reason about the temporal nature of the clinical environments they attempt to model. Because all difficult medical problems have significant temporal features, designers of medical decision support systems must recognize the unique problems caused by representing and reasoning with temporal concepts. This report has three goals. 1) to describe a set of fundamental issues in creating and reasoning with computer models of a changing clinical environment, 2) to present a taxonomy for characterizing the temporal characteristics of computer models of temporal reasoning, and 3) to use this taxonomy to compare the models of time used in some implemented medical decision-support programs. From this examination, it is argued that computational models of time based on a single uniform representational or inferential method are limited by the expressive power of that method. Multiple modeling formalisms that express different temporal properties of the do main task and that work cooperatively are required to capture the subtlety and diversity of temporal features used in expert clinical problem solving. As an example of this approach, the author describes a program called TOPAZ that contains two temporal models that represent different temporal features of the clinical domain. Key words: temporal reasoning and rep resentation; computer-based problem solving; physiologic models and simulation. (Med Decis Making 1991;11:249-264)
A Randomized Comparison of Alternative Formats for Clinical Simulations
Authors: Friedman Charles P. , France Cynthia L. , Drossman Douglas D.
Published: March 2007

Computer-based clinical simulations for medical education vary widely in structure and for mat, yet few studies have examined which formats are optimal for particular educational settings. This study is a randomized comparison of the same simulated case in three formats: a "pedagogic" format offering explicit educational support, a "high-fidelity" format attempting to model clinical reasoning in the real world, and a "problem-solving" format that requires students to express specific diagnostic hypotheses Data were collected from rising third- year medical students using a posttest, attitudinal questionnaire, students' writeups of the case, and log files of students' progress through the simulation. Student performances on all measures differed significantly by format. In general, students using the pedagogic format were more proficient but less efficient. They acquired more information but were able to do proportionately less with it. The results suggest that the format of computer-based simulations is an important educational variable. Key words. medical education, undergraduate; clinical reasoning; computer-assisted instruction. (Med Decis Making 1991;11:265-272)
Filtering Strategies in Mass Population Screening for Colorectal Cancer
Authors: Walker Andrew , Whynes David K.
Published: March 2007

On the basis of clinical trial data, 13 strategies for initial screening (filtering) for colorectal cancer are modeled for the purpose of economic evaluation. A wide range of detection cost estimates are generated, although ranking options by detection cost ignores the important consideration of undetected cancers. Formulating the problem as one of cost-effectiveness, however, allows the authors to demonstrate that members of a subset of strategies uniquely outperform all others and that the optimum strategy can be identified by the ex ante spec ification of the valuation of cancers missed on screening. Key words cancer; colorectal cancer; mass population screening; fecal occult blood test; colonoscopy; diagnostic inves tigation; cost-effectiveness; economic evaluation. (Med Decis Making 1992;12:2-7)
A Method for the Measurement of Outpatient Resource Utilization
Authors: Hooshiari Alireza , Khorramshahgol Reza
Published: March 2007

A method for measuring outpatient resource utilization in terms of the amounts of time different categories of patients spend with various providers is described. Patients are cat egorized based on selected attributes, but other attributes could be used. The method is based on two important and measurable variables. 1) frequencies of usage of different resources (e.g., nurse practitioners, physicians, x-ray), and 2) amounts of time used, by each provider type and by ancillary services (x-ray). Using the quantitative measures described, an algorithm is developed for measuring the direct labor costs of delivering primary care to different types of primary care patients. Key words resource utilization measurement, hos pital management. (Med Decis Making 1992;12:15-21)
Off Bayes
Authors: Diamond George A.
Published: March 2007

Estimates of sensitivity and specificity can be biased by the preferential referral of patients with positive test responses or ancillary clinical abnormalities (the "concomitant information vector") for diagnostic verification. When these biased estimates are analyzed by Bayes' theorem, the resultant posterior disease probabilities (positive and negative predictive ac curacies) are similarly biased. Accordingly, a series of computer simulations was performed to quantify the effects of various degrees of verification bias on the calculation of predictive accuracy using Bayes' theorem. The magnitudes of the errors in the observed true-positive rate (sensitivity) and false-positive rate (the complement of specificity) ranged from + 11% and +23%, respectively (when the test response and the concomitant information vector were conditionally independent), to + 16% and + 48% (when they were conditionally non- independent) These errors produced absolute underestimations as high as 22% in positive predictive accuracy, and as high as 14% in negative predictive accuracy, when analyzed by Bayes' theorem at a base rate of 50%. Mathematical correction for biased verification based on the test response using a previously published algorithm significantly reduced these errors by as much as 20%. These data indicate 1) that selection bias significantly distorts the determination of predictive accuracies calculated by Bayes' theorem, and 2) that these distortions can be significantly offset by a correction algorithm Key words: diagnosis, pre dictive accuracy; selection bias; sensitivity, specificity, testing. (Med Decis Making 1992;12: 22-31)
Relation of Physicians' Predicted Probabilities of Pneumonia to Their Utilities for Ordering Chest X-rays to Detect Pneumonia
Authors: Heckerling Paul S. , Tape Thomas G. , Wigton Robert S.
Published: March 2007

To investigate the relation between physicians' predicted probabilities of pneumonia and their utilities for ordering chest x-rays to detect pneumonia, the authors studied 52 physicians who ordered chest x-rays of 886 patients presenting to an emergency department with fever or respiratory complaints Physicians estimated the probability of pneumonia prior to obtaining the results of the chest x-ray. Utilities were assessed by asking physicians to consider a hypothetical patient presenting with acute respiratory symptoms, with unknown chest x-ray status, and to rank on a scale from +50 ("best thing I could do") to - 50 ("worst thing I could do") their rating scale utilities for not diagnosing pneumonia and not ordering a chest x-ray when the patient had pneumonia (i.e, missing a pneumonia), and for diagnosing pneumonia and ordering a chest x-ray when the patient did not have pneumonia (i.e, ordering an unnecessary x-ray) The utility for ordering an unnecessary x-ray was negatively correlated with average predicted probability (r = -0 1495, p = 0 29), whereas the utility for missing a pneumonia was positively correlated with average predicted probability (r = 0 2254, p = 0.11), although the correlations were not statistically significant. Relative chagrin, defined as the difference in these utilities, was significantly inversely correlated with average predicted probability (r = -0 2992, p < 0.035), even after adjusting for the prevalence of pneumonia seen by each physician (partial r = - 0.42, p < 0 0027). It is concluded that physicians who experienced greater regret over missing a pneumonia than over ordering an unnecessary x-ray estimated lower probabilities of pneumonia for patients for whom they ordered x-rays. Thus, these physicians may have had lower thresholds for ordering chest x-rays for patients with acute respiratory illness. Key words: prediction, probability; utility, pneumonia. (Med Decis Making 1992;12:32-38)
Application of Logistic Regression to the Analysis of Diagnostic Data
Authors: Knottnerus J. André
Published: March 2007

In the analysis and presentation of diagnostic relationships by means of conventional multiple logistic regression, the following limitations occur. 1) the model starts not from the prior disease odds but from the posterior disease odds for all test variables having a zero value, 2) apart from the odds ratio, other test characteristics cannot be read from the model ; 3) the sequence of entering of terms is guided by pure statistical criteria and not primarily by the criterion gain in certainty; 4) interactions are not very comprehensibly represented and are difficult to interpret. A method dealing with these limitations with respect to the analysis of data on the relationships between binary tests and disease outcome is described. Essential is the transformation of any test variable x to (x - x0), where x0 is that specific (virtual) value of x so that: posterior disease odds = prior disease odds, and consequently LR x0 = 1 Moreover, a simple branching structure is introduced while the terms are entered in order of decreasing gain in certainty. Examples are given for one-, two-, and three-test situations with and without dependency and interaction of tests, and general formulas are presented. For situations with the same prior probability, and the same overall discrimination of the separate test variables, all equations clearly have a common basis. Inclusion of new variables does not affect coefficients previously included in the model, and terms without a significant contribution can be skipped without affecting other coefficients. Standard errors and confi dence intervals of test characteristics can be computed using the BMDP® LR program. Further study needs to be done on the inclusion of continuous variables and cost-benefit aspects, and comparison with the performance of the CART® program. Key words logistic regression, Bayes' theorem; dependency; Interaction, sequence, multiple testing. (Med Decis Making 1992; 12:93-108)
Use of formal Methods in Medical Decision Making
Authors: Böckenholt Ulf , Weber Elke U.
Published: March 2007

Apparent low usage of formal decision techniques by general clinicians has raised questions about dissemination methods and about the techniques' perceived usefulness. Two literature searches examined whether use of formal decision techniques among clinicians had indeed failed to increase from the 1970s to the 1980s. A general MEDLINE search for the period 1983-87 relative to 1973-77 indicated that usage of formal decision techniques had more than doubled. This increase, however, was due to increased coverage of formal decision techniques in specialist methods journals. A manual search of seven major clinical journals and a MEDLINE search restricted to the clinical journals of the manual search disclosed no increase in overall usage for the same time periods. MEDLINE detected only a small subset of the actual instances of formal method usage found by the manual search. Individual medical subspecialties were found to utilize different formal decision techniques to different degrees. The authors suggest interventions that may increase the usage of formal decision techniques among general clinicians. Key words: decision analysis; decision automation; decision trees; Bayes'theorem; sensitivity analysis; ROC analysis; formal modeling. (Med Decis Making 1992;12:298-306)
Should Canada and the United States Universally Vaccinate Infants against Hepatitis B?
Authors: Krahn Murray , Detsky Allan S.
Published: March 2007

This paper examines the economic attractiveness of universal vaccination of infants with hepatitis B virus (HBV) vaccine by calculating the incremental cost-effectiveness of this strategy when compared with the currently recommended strategy of screening all pregnant women and vaccinating only infants born to HBsAg+ mothers. A decision-analytic model involving a Markov process to model the long-term sequelae of HBV infection was constructed to estimate the expected costs and life expectancies for a cohort of newborns under two strategies: the current screening policy (SELECTIVE), which involves active and passive vac cination of infants born to carrier mothers, and a policy that combines the current screening strategy (including active and passive vaccination of infants born to carriers) with active vaccination alone for children of non-carriers (UNIVERSAL). A hypothetical cohort of children born in either Canada or the United States in 1991 was examined. Cost estimates were derived for Ontario. From a societal perspective, the incremental cost required to achieve one extra life year was found to be $30,347, comparable to the cost-effectivenesses of other health care strategies commonly used in North America. The result is sensitive to the duration of vaccine effectiveness and particularly to the price of the vaccine. Universal vaccination results in net cost saving at a vaccine price of approximately $7 per dose, from a societal perspective. It is concluded that universal vaccination against HBV in infancy is economically attractive, comparable in cost-effectiveness to existing health care interven tions. Lower vaccine prices would substantially improve the attractiveness of such a program. Implementation of universal vaccination should be considered in North America, contingent on vaccine price reduction. A monitoring program to ensure the long-term efficacy of the vaccine should be part of such a program. Key words: vaccination; hepatitis B; cost-effec tiveness; prevention; chronic hepatitis. (Med Decis Making 1993;13:4-20)
A Prototype Decision Support System for Differential Diagnosis of Psychotic, Mood, and Organic Mental Disorders
Authors: Moreno Henry R. , Plant Robert T.
Published: March 2007

The authors designed a decision support system to assist mental health professionals to perform differential diagnoses of psychotic, mood, and organic mental disorders in accor dance with the American Psychiatric Association's revised third edition of the Diagnostic and Statistical Manual of Mental Disorders. A prototype system arrived at through a rigorous methodology illustrates a style of development that attempts to ensure system maintainability, correctness, and consistency of deduction and promotes high quality in software. Key words: mental disorders; decision support system; computer-assisted diagnosis; expert systems; artificial intelligence. (Med Decis Making 1993;13:43-48)
A Comparison of Two Methods for Indexing and Retrieval from a Full-text Medical Database
Authors: Hersh William R. , Hickam David H.
Published: March 2007

The objective of this study was to compare how well medical professionals are able to retrieve relevant literature references using two computerized literature searching systems that provide automated (non-human) indexing of content. The first program was SAPHIRE, which features concept-based indexing, free-text input of queries, and ranking of retrieved references for relevance. The second program was SWORD, which provides single-word searching using Boolean operators (AND, OR). Sixteen fourth-year medical students partici pated in the study. The database for searching was six volumes from the 1989 Yearbook series. The queries were ten questions generated on teaching rounds. All subjects searched half the queries with each program. After the searching, each subject was given a ques tionnaire about prior experience and preferences about the two programs. Recall (proportion of relevant articles retrieved from the database) and precision (proportion of relevant articles in the retrieved set) were measured for each search done by each participant. Mean recall was 57.6% with SAPHIRE; it was 58.6% with SWORD. Precision was 48.1% with SAPHIRE VS 57.6% with SWORD. Each program was rated easier to use than the other by half of the searchers, and preferences were associated with better searching performance for that program. Both systems achieved recall and precision comparable to existing systems and may represent effective alternatives to MEDLINE and other retrieval systems based on human indexing for searching medical literature. Key words: information retrieval systems; auto mated indexing; medical literature; MEDLINE. (Med Decis Making 1993;13:220-226)
Nurses' Fear of Contagion
Authors: Rundall Christine S. , Weiss David J.
Published: March 2007

The amounts of fear of contagion aroused in nurses by 15 unnamed diseases were examined. The diseases were chosen to allow factorial arrangement according to their degrees of transmissibility and the severities of their prognoses. Concern about contagion was hypoth esized to increase as transmissibility increased and as prognosis worsened, in accord with a multiplicative model. The model was tested with functional measurement procedures, because this method allows simultaneous evaluation of the descriptive accuracy of the proposed model and validation of the rating scale. The model was supported graphically and statistically. Nurses' worries were found to have the regularity prescribed by a multi plicative process. Although one of the diseases was constructed to simulate the character istics of AIDS, no magnification of fear was found in relation to other deadly and infectious diseases. Key words: fear of contagion; functional measurement; multiplicative model; nurses. (Med Decis Making 1994;14:40-46)