bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of clonidine and diazepam on the acoustic startle response and on its inhibition by 'prepulses' in man
Authors: Abduljawad K.A.J. , Langley R.W. , Bradshaw C.M. , Szabadi E.
Published: March 2007

This experiment examined the effects of two sedative/anxiolytic drugs, diazepam and clonidine, on the eyeblink component of the acoustic startle response in healthy volunteers. Twelve males (18-30 years), screened for normal hearing thresholds, participated in three sessions in which they received oral doses of placebo, diazepam 10 mg and clonidine 200 μg according to a balanced double-blind protocol. Thirty-minute electromyographic recordings from the orbicularis oculi muscle of the right eye were carried out 120 min after ingestion of clonidine and 60 min after ingestion of diazepam. Subjects received 36 40-msec sound pulses (115 dB), separated by variable intervals (mean 25 sec); in 24 of the trials the pulse was preceded by a 40-msec prepulse (75 dB in 12 trials and 85 dB in 12 trials; prepulse-pulse interval, 120 msec). The amplitude of the startle response was significantly reduced both by diazepam (mean±SEM: -43.9±7.4%) and by clonidine (-75.7±4.7%). Under the placebo condition, the 75 and 85 dB prepulses inhibited the startle response by 38.6 ± 6.5 and 70.3 ± 2.9%, respectively. Neither drug significantly altered the degree of prepulse inhibition. Both drugs reduced self-rated alertness; clonidine reduced systolic blood pressure and salivation. The results confirm the suppressant effect of clonidine on the startle response and show a qualitatively similar effect of diazepam; the results also demonstrate the insensitivity of prepulse inhibition of the startle response to doses of sedative drugs that are sufficient to attenuate the startle response itself.
Reviews : Pharmacotherapy of adolescent attention deficit hyperactivity disorder: challenges, choices and caveats
Authors: Garland E. Jane
Published: March 2007

A recent increase in stimulant treatment of adolescents with attention deficit hyperactivity disorder (ADHD) has been documented. Challenges in treating adolescent ADHD with methylphenidate or dextroamphetamine include compliance with frequent dosing, abuse potential and wear-off or rebound effects. Co-morbid anxiety, occurring in at least 30 percent of ADHD youths, is associated with lower rate of response to stimulants. The effective alternatives, tricyclic antidepressants or pemoline, are each associated with rare but serious toxicity. Bupropion has recently proven effective in controlled trials. Other noradrenergic or dopamine-enhancing agents such as venlafaxine and nicotine show some benefit in open trials. The need for more options in pharmacotherapy of ADHD is evidenced by rapid adoption in clinical practice of alternative and adjunctive medication despite lack of controlled research on efficacy and safety.

The indications for long-term stimulant treatment of ADHD present some controversy, and highlight a need for more research on safety and efficacy through the lifespan. Thresholds for diagnosis are much lower with DSM than with ICD, and thresholds for treatment are contentious, given the performance-enhancing effects of stimulants in normal students. The endpoint for treatment is unclear, as stimulants are also effective in adult ADHD. Based on short- and intermediate-term studies to date, stimulant medication is clearly more efficacious than cognitive and behavioral strategies for the symptoms of ADHD. Longer term research is needed to determine whether sustained stimulant therapy will reduce the adverse emotional, behavioral and academic consequences of inattention and impulsivity in adolescents and adults.
Some Perceptions of the Implications of High Technology for Minnesota Schools
Authors: Westby Sandra B.
Published: March 2007

Advances in technology are accelerating the momentum for change in all sectors of society. There is at present a lag time between the actual development and implementation of new technology and the public consciousness of the issues involved. The rapid rate of social change, however, emphasizes the critical role of the educational system and the need to continually estimate and evaluate direction to best serve the common good. Forty-five influential Minnesota leaders in education, business/industry and government were interviewed on issues related to education and the changing economy.
Diagnostic Imaging System Evaluation
Authors: Goin James E. , DeSmet Arthur A.
Published: March 2007

The purpose of this paper is to introduce new methodology for the evaluation of diagnostic imaging systems based on the assessment of diagnostic features by human observers. This methodology is intended to supplement the usual receiver operating characteristic (ROC) curve approach to imaging system evaluation. The approach is based on measuring the experimental evidence of a priori scientific propositions. The methodology requires simple calculations that can be implemented by clinical inves tigators. An example, based on diagnosis of sacroiliitis, is given to illustrate the method's usefulness in a diagnostic situation. (Med Decis Making 2:311-321, 1982)
A Structural Method to Guide Test Evaluation
Authors: Politser Peter E.
Published: March 2007

This paper describes a conceptual framework to guide the evaluation of diagnostic tests in medicine. The framework systematically generates questions about possible test uses and factors that can modify their value. (Med Decis Making 5:417-436, 1985)
Looking for "Indicants" in the Differential Diagnosis of Jaundice
Authors: Boom R. , Gonzalez C. , Fridman L. , Ayala J.F. , Realpe J.L. , Morales P. , Quintero R.
Published: March 2007

The differential diagnosis between intra- and extrahepatic causes of jaundice was studied. At the "20 Noviembre" ISSSTE Hospital in Mexico City, between January 1977 and May 1984, data were collected in 1,263 jaundiced patients. To the clinical data for 1,000 of these 1,263 patients and a new set of 105 jaundiced patients, the COMIC study group algorithm was applied. The differential diagnosis between medical and surgical causes of jaundice was correct in 90% of the cases. In 85% the algorithm could also differentiate between acute and chronic disease, or between benign and malignant causes of jaundice. The COMIC algorithm was then modified and applied to the same 1,000 cases examined previously, with 96% accuracy in distinguishing medical and surgical causes of jaundice and 94% accuracy in discriminating between acute and chronic, or benign and malignant, disease. In a new set of 105 cases of jaundiced patients the modified COMIC algorithm made the correct diagnosis between intra- and extrahepatic causes for 98% of the patients, and for 93% it was also capable of distinguishing benign from malignant and acute from chronic causes of jaundice. Key Words: differential diagnosis; discriminant analysis; indicants; COMIC algo rithm. (Med Decis Making 6:36-41, 1986)
An Eualuation of Clinicians' Subjective Prior Probability Estimates
Authors: Dolan James G. , Bordley Donald R. , Mushlin Alvin I.
Published: March 2007

The degree of consensus and the accuracy of subjective prior probability estimates made by 104 clinicians were examined. The clinicians' estimates were compared with objective prior probabilities obtained from published sources and actual patient outcomes. Each cli nician made seven estimates based upon written case summaries abstracted from patient records. Consensus was measured by calculating estimate ranges and standard deviations. The clinicians' estimates varied widely: the smallest range was 80 (2%-82%); four of the seven probability ranges were greater than 90. The average standard deviation was 19.5. Using these prior probabilities and Bayes' theorem, widely varying posttest probabilities would result after many common diagnostic tests. Accuracy was measured using the Brier score, which ranges from 0 to 1; a score of 0 indicates perfect accuracy. The clinicians' Brier scores ranged from 0.05 to 0.57. The objectively determined probabilities achieved a Brier score of 0.11, better than that of 96% of the clinicians. Clinical experience did not consistently affect estimate accuracy or consensus. The clinicians' subjective estimates were inaccurate measures of the prior probability of disease. There was little consensus regarding disease likelihood among the clinicians. Objective prior probabilities were more accurate and less variable. Key words: diagnosis; decision making; probability. (Med Decis Making 6:216- 223, 1986)
The Determinants of Treatment Choice in End-stage Renal Disease
Authors: Deber Raisa B.
Published: March 2007

Practitioner judgments about treatments for hypothetical end-stage renal disease patients were examined by two mailed surveys. It was hypothesized that treatment choice was a function of four hierarchically arranged sets of factors: disease- and treatment-specific, pa tient-specific, environment- and institution-specific, and practitioner-specific. The first survey identified six vignettes for which the case-specific factors alone did not yield a generally accepted treatment decision. These six cases were used in the second survey, whose results are reported here. Practitioner-specific characteristics were found to be only weakly related to treatment choice. Guttman scale analysis showed no significant practitioner propensity to use any given treatment. Instead, the number of colleagues in a respondent's renal unit picking a given therapy for a given patient was the strongest predictor of an individual's choice. Contextual factors—clinical details of the case and decision rules within the insti tution—appeared to overwhelm provider-specific tendencies; characteristics of the decision generally outweighed characteristics of the decision maker. This framework of factors may be useful for analyzing inter-provider variation. Consequences for certain approaches to the study of decision making (especially single-site studies and regression-based models) are noted. Key words: choice behavior; health services research; kidney failure, chronic; he modialysis ; peritoneal dialysis; transplantation. (Med Decis Making 6:231-238, 1986)
Knowledge Acquisition and Veritication Tools for Medical Expert Systems
Authors: Mars Nicolaas J.I. , Miller Perry L.
Published: March 2007

Expert systems require large amounts of domain knowledge for non-trivial problem solving. Experience in developing such systems has shown that the processes of acquiring domain knowledge (knowledge acquisition) and of determining whether the knowledge is consistent, complete, and correct (knowledge verification) are major problems. This paper discusses various tools developed to assist in these two processes. These tools bring additional knowl edge to bear, or provide better interfaces between a knowledge engineer and the expert system's knowledge. Key words: expert systems; knowledge-based systems; artificial in telligence ; knowledge acquisition; knowledge verification. (Med Decis Making 7:6-11,1987)
Surgery or Angioplasty for Cost-effective Renal Revascularization?
Authors: England William L. , Roberts Stephen D. , Grim Clarence E.
Published: March 2007

The authors retrospectively compared the cost-effectiveness of percutaneous transluminal angioplasty with that of renal artery bypass surgery for treating renal artery stenosis, using the experiences of 52 patients treated for renovascular hypertension between 1977 and 1983. The expected results of treatment for angioplasty and surgery were taken from pub lished literature and from experience. Based on the analysis, angioplasty is recommended for treating patients with fibromuscular disease, and patients less than 50 years old, while surgery is the preferred treatment for older patients and those with atherosclerotic disease. These strategies not only minimize the cost per life-year gained from treatment, but also maximize the life expectancy of treated patients. The results are quite robust for the discount rate used in the cost calculations, for variations in the expected rate of stenosis recurrence, and for variations in the treatment outcome probabilities. Key words: hypertension; renal artery stenosis; cost-effectiveness analysis; angioplasty; computer simulation. (Med Decis Making 7:84-91, 1987)
Intermediate, Indeterminate, and Uninterpretable Diagnostic Test Results
Authors: Simel David L. , Feussner John R. , Delong Elizabeth R. , Matchar David B.
Published: March 2007

Diagnostic tests do not always yield positive or negative results; sometimes the results are intermediate, indeterminate, or uninterpretable. No consensus exists for the incorporation of such results into data assessment. Conventional Bayesian analysis leads investigators to either exclude patients with non-positive, non-negative results from their studies or categorize such results into inappropriate cells of the standard four-cell decision matrix. The authors propose a standardized method for reporting results in studies dealing with diagnostic test use and discuss how researchers should expand the four-cell matrix to six cells when non- positive, non-negative results occur. They suggest that the six-cell matrix with new operational definitions of sensitivity, specificity, likelihood ratios, and test yield should be adopted rou tinely. In addition, they define the different types of non-positive, non-negative results and demonstrate how clinicians can use tree-structured decision analysis from the six-cell matrix. While their method does not solve all problems posed by non-positive, non-negative results, it does suggest a standard method for reporting these results and utilizing all the data in decision making. Key words: diagnostic tests, Bayes theorem, decision analysis. (Med Decis Making 7:107-114, 1987)
Symptom Severity and Patients' Values in the Decision to Perform a Transurethral Resection of the Prostate
Authors: Krumins Peter E. , Fihn Stephan D. , Kent Daniel L.
Published: March 2007

To develop and validate a method to assess patients' subjective values for outcomes of surgical and nonsurgical management of benign prostatic hypertrophy (BPH), the authors studied 20 patients who had symptoms of BPH. Eight were scheduled for prostatic surgery and 12 were not. They conducted an interview, including a time-trade-off (TTO) exercise to elicit values for single and combined outcomes and questions about symptoms used to complete a symptom severity score. Expected gain and symptom severity were independent and significant (p <0.001 for both comparisons) determinants of whether surgery was sched uled, while the correlation between these two factors was limited (Spearman = 0.058, p = 0.004). Based on a decision analytic model incorporating TTO values, a high expected gain in quality from surgery was strongly related to whether surgery was scheduled (p = 0.002), and had a higher positive predictive value (0.86) than symptom severity score (0.73). This small study demonstrates the feasibility and validity of using value assessment in this setting and suggests that this approach can be useful to clinicians when counseling patients. Key Words: transurethral resection of the prostate (TURP); benign prostatic hypertrophy (BPH); decision analysis; patient values. (Med Decis Making 8:1-8, 1988)
Status of Researches on Medical Dialectics in China
Authors: Yan-Ting Huang
Published: March 2007

In 1984, Huang Yan-ting, MD, spent some months in the United States studying surgical techniques. During his stay he met with Dr. Lee Lusted, then Editor-in-Chief of Medical Decision Making, and the two had several discussions about the field of medical decision making. Dr. Huang published a note on the status of the Society for Medical Decision Making in National Medical Journal ofchina (65:502) in 1985 (also published in MDM, 5:475- 476, 1985). This is Professor Huang Yan-ting's second status report, received by Dr. Lusted.— DGF
The Relationship Between Managerial and Clinical Decision Making in the Hospital
Authors: Griner Paul F.
Published: March 2007

This paper is based on an invited address before a plenary session of the Ninth Annual Meeting of the Society for Medical Decision Making, Philadelphia, October 1987. Paul F. Griner, MD, is General Director of Strong Memorial Hospital and Samuel E. Durand Professor of Medicine, University of Rochester School of Medicine and Dentistry. We are grateful to Dr. Griner for making his text available to us.—DGF
Objective Criteria for In-vitro Responses in Human Tumor Colony-forming Assays
Authors: Koziol James A. , Petkau A. John , Taetle Raymond
Published: March 2007

The application of rigorous statistical criteria to the design and analysis of in-vitro assay techniques can lead to more reliable assessments of their utility. The authors demonstrate that an objective criterion for in-vitro drug sensitivity would yield less pronounced false- negative error rates than a fixed-cutoff rule, and would therefore be more suitable for screen ing of putative chemotherapeutic agents. Key words: drug sensitivity testing; objective criteria. (Med Decis Making 8:304-309, 1988)
Revision of Diagnostic Logic Using a Clinical Database
Authors: Haug Peter , Clayton Paul D. , Shelton Pamela , Rich Tracy , Tocino Irena , Frederick Philip R. , Crapo Robert O. , Morrison William J. , Warner Homer R.
Published: March 2007

Statistical pattern-recognition techniques have been frequently applied to the problem of medical diagnosis. Sequential Bayesian approaches are appealing because of the possibility of generating the underlying sensitivities, specificities, and prevalence statistics from the estimates of medical experts. The accuracy of these estimates and the consequences of inaccuracies carry implications for the future development of this type of system. In an effort to explore these subjects, the authors used statistics derived from a clinical database to revise the diagnostic logic in a Bayesian system for generating a differential diagnostic list. Substantial changes in estimated a priori probabilities, sensitivities, and specificities were made to correct for significant under- and overestimations of these values by a group of medical experts. The system based on the derived values appears to perform better than the original system. It is concluded that the statistics used in a Bayesian diagnostic system should be derived from a database representative of the patient population for which the system is designed. Key words: diagnosis; computer-assisted; Bayes theorem; lung dis eases. (Med Decis Making 1989;9:84-90)
What Difference Do Two Days Make? The Inertia of Physicians' Sequential Prognostic Judgments for Critically III Patients
Authors: Poses Roy M. , Bekes Carolyn , Copare Fiore J. , Scott William E.
Published: March 2007

Medical authorities have asserted the importance of observing a patient's clinical course over time. Distinguished committees have suggested that changes over time in physicians' prognostic estimates should influence decisions to transfer patients out of intensive care units (ICUs). This study evaluated how the opportunity to observe patients over time affected physicians' prognostic estimates for a cohort of 269 critically ill patients sequentially admitted to a medical-surgical ICU in a teaching hospital. As soon as possible after admission and again 48 hours later, the authors obtained a quantitative estimate of the probability of survival through hospital discharge from each patient's house officer and primary attending physician, and the critical care attending physician on duty. They independently determined each patient's survival. From this population they analyzed 181 pairs of judgments made by the same house officers, 211 pairs by the same primary attendings, and 172 pairs by the same critical care attendings. The physicians' 48-hour estimates were little changed from their previous estimates for the same patients. The correlation coefficient for the house officers' paired estimates was 0.84 (p <0.0001 ); for the critical care attendings' estimates 0.84 (p <0.0001), and for the primary attendings' estimates, 0.90 (p <0.0001). Forty-eight hours did not substantially reduce the disagreements present between estimates made by different physicians for the same patient. No group of physicians substantially improved the reliability or the discriminating power of its later estimates. The physicians in the study could not take advantage of sequential clinical information over time. These results point out the need to teach physicians how to better integrate and process sequential clinical data. Key words: sequential data; prediction; survival rate; prognosis; intensive care unit. (Med Decis Making 1990;10:6-14)
Local versus Global Measures of Accuracy
Authors: Black William C. , Dwyer Andrew J.
Published: March 2007

Unlike many tests, diagnostic imaging provides information about the location of disease, in addition to its presence or absence. To account for this ability of imaging, the authors make the distinction between local and global measures of accuracy. Local pertains to each anatomic site of potential disease in the patient and the corresponding image, while global refers to all such sites, collectively. After making this distinction, the authors demonstrate two major problems with global sensitivity and specificity, which are more commonly reported than their local counterparts. First, global sensitivity, unlike local sensitivities, varies with the anatomic distribution of disease in the reference population. Second, the conventional global measures cannot be integrated with pretest knowledge about the anatomic distribution of disease. Consequently, predictive values based on global sensitivity and specificity under estimate the probability of disease when imaging and clinical findings correlate anatomically and overestimate the probability when the findings do not correlate. The local versus global distinction supports the commonsense notion that information pertaining to the anatomic distribution of disease is crucial for test interpretation.
Determining a Range of False-positive Rates for Which ROC Curves Differ
Authors: McClish Donna Katzman
Published: March 2007

Many indices have been proposed for summarizing the information contained in the ROC curve. When comparing two ROC curves, though, there are times when global summary measures are either not optimal or not appropriate. The author presents a method for directly comparing true-positive rates for two diagnostic, screening or prognostic tools, determining over what range of false-positive values the tests differ. The method is applicable for in dependent or dependent samples. An example concerning gallium citrate imaging is pre sented, as well as an example using a prognostic index for severity of illness in the ICU. The range of false-positive rates for which the ROC curves differ is determined for each example.
Comparison of Different Treatment strategies for Diffuse Large-cell Lymphomas
Authors: Djulbegovic Benjamin , Hollenberg James , Woodcock Thomas M. , Herzig Roger
Published: March 2007

There are more than 20 drug combinations in use for the treatment of diffuse large-cell non- Hodgkin's lymphoma (NHL). New treatments have been developed without prior comparison in clinical trials. The authors devised a Markov-process model to compare the efficacy of a first-generation combination chemotherapy regimen (CHOP) with that of a third-generation regimen (MACOP-B) using currently available data. For a typical 57-year-old male patient, life expectancy with MACOP-B was 12.1 years, compared with 8.3 years with CHOP. The remission rate after initial treatment and the functional status after the first remission is achieved were the most important determinants of life expectancy. It was still possible for CHOP to become better strategy provided that the initial remission rate with MACOP-B were lower than 50% or that functional status after remission was achieved were less than 66%. The analysis suggests that the most effective therapeutic regimen for diffuse large-cell lymphoma must not only result in a high remission rate but also cause minimal late sequelae. These two parameters were incorporated into the nomogram, which can serve as a basis for comparison of the efficacy of any chemotherapeutic regimen in non-Hodgkin's lymphoma. Key words: decision analysis; Markov model; non-Hodgkin's lymphoma; chemotherapy. (Med Decis Making 1991;11:1-8)
Qualitative Probability versus Quantitative Probability in Clinical Diagnosis
Authors: Chard Tim
Published: March 2007

The use of Bayes' theorem as a diagnostic tool in clinical medicine normally requires an input of exact probability estimates. However, humans tend to think in categories ("likely," "unlikely," etc.) rather than in terms of exact probability. A computer simulation of the pre senting features of a case of pelvic infection has been used to compare the effects of quantitative and qualitative probability estimates on the diagnostic accuracy of Bayes' theo rem. For the commoner conditions (prior probability ≥ 0.2) the use of a two- or three-category system is virtually equivalent to the use of exact probability. However, uncommon conditions (prior probability ≤ 0.03) are completely ignored by the qualitative system. It is concluded that the use of simple categories of probability is acceptable for a Bayesian diagnostic system provided that the target conditions have a relatively high prior probability. Key words: Bayes' theorem; quantitative probability; qualitative probability; computer simulation. (Med Decis Making 1991;11:38-41)
Signal Detectability
Authors: Centor Robert M.
Published: March 2007

Issues related to ROC curves are addressed. The original article on the subject by Lee Lusted, describing the "state of the art" 20 years ago, is reviewed. The concepts that Lusted addressed are then expanded, suggesting the current state of the art. New issues that have arisen with regard to ROC curves and their use in medicine are addressed. Finally, potential areas for future investigation are suggested.
The Use of a Markov Process to Simulate and Assess Follow-up Policies for Patients with Malignant Disease
Authors: Munro Alastair J. , Warde Padraig R.
Published: March 2007

Using a Markov process to simulate and assess surveillance policies for stage I nonsemi nomatous germ cell tumors, the authors analyzed costs and effectiveness for the various policies that have been used clinically. They found no real differences in effectiveness, defined as probability of surviving two years, between the policies. There were significant differences in costs. The model is used to suggest schedules that might be more cost- effective than those currently employed. The model suggests that computed tomographic scanning of the abdomen may not be essential to the effectiveness of surveillance protocols.
Using the ID3 Algorithm to find Discrepant Diagnoses from laboratory Databases of Thyroid Patients
Authors: Forsström Jari , Nuutila Pirjo , Irjala Kerttu
Published: March 2007

Rare cases are a central problem when an expert system is constructed from example cases with machine learning techniques. It is difficult to make a decision support system (DSS) to cover all possible clinical cases. An inductive learning program can be used to construct an expert system for detecting cases that differ from routine cases. The ID3 algorithm and the pessimistic pruning algorithm were tested in this study: a DSS was built directly from the data of patient records. A decision tree was generated, and the cases misclassified by the decision tree as compared with the classifications of a clinician were listed on a checklist, which formed the feedback to the clinician. In clinical situations about 5-10% of functional thyroid disorders may be misclassified. At this error level, the method found over 90% of the errors with a specificity of 95%. In simple medical classification tasks this dynamic self- learning system can be used to create a DSS that can assist in the quality control of clinical decision making. Key words: expert systems; automated data processing; computer-assisted diagnosis; medical decision making; thyroid disorders. (Med Decis Making 1991;11:171- 175)
Benign and Malignant Breast Disease
Authors: Llewellyn-Thomas H.A. , Sutherland H.J. , Tritchler D.L. , Lockwood G.A. , Till J.E. , Ciampi A. , Scott J.F. , Lickley L.A. , Fish E.B.
Published: March 2007

The study purpose was to determine whether differences in the weights assigned to various dimensions of health by 90 women in three subgroups (benign breast disease, breast cancer receiving chemotherapy, and breast cancer receiving other therapies) were associated with differences in self-reported health status in these dimensions. Two methods, one direct and the other indirect, were used to elicit values for mobility, depression, and social support. Two different scales also provided self-reports of health status in each of these dimensions. These measures, in conjunction with sociodemographic variables, were used to test for status- value relationships. No statistically significant association between health values and health status was observed. The absence of any detectable association may have been a result of methodologic difficulties in assessing broadly defined dimensions of health. A possible solution would be to use "individualized" dimensions that are uniquely important to the individual, and to take into account such factors as possible influences of past health status and values, and possible gaps between expected health status and health status actually experienced. Key words: health status measurement; patients' values; utility assessment. (Med Decis Making 1991 ;11 :180-188)
Scotched on the ROCs
Authors: Diamond George A.
Published: March 2007

In the last four years an active debate has been conducted in this journal about single-parameter ROC curves and methods for correcting curves that have been subjected to verification bias. The major discussants in this debate have produced these three commentaries on a study recently published in MDM. As a researcher I conclude that Diamond's single-parameter ROC, while conceptually attractive and easy to use, is not free from the verification bias that can be found in many diagnostic assessment studies. As Editor I judge that enough space has been devoted to this problem for the time being. Let the scientific community sort through the material already presented on this topic. May it lead to clinical studies wherein single- parameter ROCs can be profitably applied.—JRB
Improving the Accuracy of Severity Indexes
Authors: Alemi Farrokh
Published: March 2007

This study explores the difference between additive and non-additive indexes in measuring the severity of myocardial infarction. It shows, as an example, the fallacy of adding severity scores in a straightforward manner. An additive severity index was constructed from the judgments of seven experts The experts also identified several exceptions to the additive index. The study used the exceptions to modify the additive index and produce a non-additive severity index. The non-additive seventy index explained 36% more of the variance in the seventy judgments made by five physicians and two nurses on 50 hypothetical cases than the additive index did. In addition, the non-additive index was 3% more accurate in predicting in-hospital mortality of 7,500 patients with myocardial infarction When the study reduced the noise in the data by ignoring 1,200 rare cases in which stable estimates of mortality rate were unavailable, the prediction of the non-additive index was 13% more accurate than that of the additive index. Statistical tests showed that the differences between the additive and the non-additive indexes were significant at an alpha level below 1% The practical impli cations of non-additive seventy indexes are discussed Researchers and physicians who assess the severity of myocardial infarction should systematically explore exceptions that may improve the accuracy of prediction of an additive index. Key words seventy indexes; additive indexes; non-additive indexes; myocardial infarction. (Med Decis Making 1992;12:8-14)
A Pitfall in Utility Assessment — Patients' Undisclosed Investment Decisions
Authors: Hilden Jørgen , Glasziou Paul P. , Habbema J. Dik F.
Published: March 2007

Among those decisions that may be made by a patient in response to an illness, the authors single out a certain class. contingent investment decisions. They are characterized by the patient's committing him- or herself, on the basis of prognostic counseling, to a certain action or non-action that he or she may regret in retrospect Examples show that, when assessing utilities, the decision analyst runs a risk of handling such investment decisions incorrectly, unless they are made explicit and incorporated into the medical decision process. The anomaly is explained as a violation of the structural rules for decision trees and is also interpreted in terms of "the price of prognostic ignorance," a quantity closely related to the expected utility value of perfect information. Key words: decision theory; physician-patient relations, patient compliance; prognosis; risk-taking, quality of life; utility theory; patients' decisions, decision trees. (Med Decis Making 1992;12:39-43)
Assessing Utilities by Means of Conjoint Measurement
Authors: Maas Arne , Stalpers Lukas
Published: March 2007

A method is presented for helping patients who have laryngeal cancer to decide between laryngectomy and radiotherapy in cases where these treatments are deemed medically equivalent. The method is based on the model of additive conjoint measurement. The treat ment with the higher utility is determined from pair comparisons among outcomes that vary in quality and quantity of life. Pair comparisons enable a (partial) test of the axioms of additive conjoint measurement. This is in contradistinction to earlier work on decision making for patients with laryngeal cancer, and most of the work in medical decision making in general, in which underlying axioms have almost never been tested. Besides testing the axioms, another important advantage of pair comparisons is that they avoid difficulties with other, risk-based, assessment procedures by presenting only riskless alternatives. Encouraging results have been found in a study among patients. Key words: utilities; additive conjoint measurement; pair comparisons; laryngeal cancer. (Med Decis Making 1992;12:288-297)
Validation of Probabilistic Predictions
Authors: Miller Michael E. , Langefeld Carl D. , Tierney William M. , Hui Siu L. , McDonald Clement J.
Published: March 2007

Current advances in high-speed computing and increased availability of statistical software have led to widespread use of statistical methods for the development of computerized protocols predictive of binary health outcomes. If these predictive algorithms are to be used in settings other than those for which they were developed, e.g., applied in a different geographic setting or extrapolated for use in a slightly different population, then they should be carefully validated to ensure appropriate application. Miller et al. (Stat Med. 1991) provided a comprehensive methodology for external validation of logistic prediction models, and ap plied these methods in a temporal validation setting. In this article, the authors emphasize how these methods can be applied to general forms of probabilistic predictions and provide several SAS® macros for computation of the desired statistics. Key words: validation; logistic regression; predictive probabilities. (Med Decis Making 1993;13:49-58)
Classic uersus Sequential Diagnostic Support for Chronic Nonspecific Respiratory Diseases
Authors: Liebhart Jerzy , Krusińska Ewa
Published: March 2007

The authors discuss two approaches to assisted medical diagnosis of chronic nonspecific respiratory diseases, Bayes-Fisher linear discrimination and a decision tree based on the linear discriminant functions of the individual nodes. Only the two most discriminative vari ables obtained for differentiation of groups at individual nodes are used for the node sub- classification. They are the four linguistic variables cough, character of dyspnea, physical examination of the chest, and x-ray examination of the chest obtained by conversion of discrete features. No laboratory finding is used. The tree classifier simulates a physician's thought process. Results with multigroup linear discrimination on the same four variables for both a reclassification and a cross-validation technique were comparable to the tree- scheme outcomes. The tree classifier lends itself to simple graphic presentation, the patient being created as a point in the plane of the two most discriminative variables without the need for mathematical formulas and posterior probabilities. The classification errors that appear in the chronic bronchitis group can be easily corrected using an additional variable, smoking index. Key words: diagnostic support; computer-aided diagnosis; linear discriminant function; tree classifier; respiratory diseases. (Med Decis Making 1993;13:103-113)
Stability of Time-tradeoff Utilities in Survivors of Myocardial Infarction
Authors: Tsevat Joel , Goldman Lee , Soukup Jane R. , Lamas Gervasio A. , Connors Kathleen F. , Chapin Carole C. , Lee Thomas H.
Published: March 2007

To investigate whether time-tradeoff utilities of survivors of myocardial infarction change over time and whether changes in utilities correlate with changes in functional status, the authors conducted serial interviews using a time tradeoff and three measures of functional status in a cohort of 67 patients who had recently had myocardial infarction. The patients were also asked to rate their overall health on a rating scale and were asked about chest pain, exercise status, and employment status. Each patient was interviewed two to five times over one and a half years. The mean (95% Cl) time-tradeoff score for all patients was 0.88 (0.84, 0.93). Over a mean interval of 8.4 months, 28 (42%) patients changed Karnofsky scores, 28 (42%) changed Specific Activity Scale classes, and 11 (16%) changed New York Heart Association classes, with most changes representing improvements in functional status. Scores on the rating scale improved by a mean (95% Cl) of 0.06 [(0.03, 0.10); p < 0.002], but scores on the time tradeoff remained stable, with a mean (95% Cl) change of 0.03 [(-0.02, 0.08); p = NS]. Changes in time-tradeoff scores did not correlate with changes in Specific Activity Scale classes (Kendall's τ = 0.21), New York Heart Association classes (τ = -0.02), or Karnofsky scores (τ = 0.14); with changes on the verbal rating scale (R = 0.20); with changes in chest pain status (τ = -0.05), exercise status (τ = 0.11), or employment status (τ = 0.11); or with interim hospitalizations (τ = 0.05). The authors conclude that, in this relatively stable group of survivors of myocardial infarction, time-tradeoff utilities remained stable, and that changes in time-tradeoff utilities did not correlate with changes in function. Key words: functional status; quality of life; utility; patient preferences; myocardial infarction. (Med Decis Making 1993;13:161-165)
Inaccuracies in Estimates of Life Expectancies of Patients with Bronchial Cancer in Clinical Decision Making
Authors: Benbassat Jochanan , Zajicek Gershom , Van Oortmarssen Gerrit J. , Ben-Dov Isachar , Eckman Mark H.
Published: March 2007

Approximations of life expectancy in clinical decision making frequently assume constant disease-specific ("excess") mortality hazards over age at diagnosis and over time from diagnosis. This assumption is inconsistent with the longer relative survival of younger patients with bladder cancer and with the declines in mortality hazards from bladder and breast cancers over time from diagnosis. To estimate the error that may result from these as sumptions, the authors derived excess mortality hazards from the Surveillance, Epidemiology and End Result (SEER) tumor registry for bronchial cancers stratified by age at diagnosis and time from diagnosis. They compared the life expectancies calculated by a model using an average constant annual cancer-specific mortality hazard over time from diagnosis with those calculated using data-derived cancer-specific annual mortality hazards that varied as a function of time from diagnosis. For younger patients with less advanced disease, the constant-average-mortality model underestimated life expectancies by up to 50% relative to those predicted by the time-variant model. For those over 75 years old at diagnosis, and for all patients with advanced disease, the constant-average-mortality model overestimated life expectancies by up to 65% relative to those predicted by the time-variant model. The authors conclude that predictions of life expectancy with bronchial cancer, and probably with other neoplasms, are limited by the widespread use of oversimplified methods of calculation and by the lack of data describing mortality hazards as a function of time from diagnosis. The assumption of a constant average cancer-specific mortality over time from diagnosis may result in inaccurate estimates of life expectancy and bias the results of clinical decision analyses. Key words: life expectancy; mortality hazards; prediction; time. (Med Decis Making 1993;13:237-244)
Are Healthy-years Equivalents an Improvement over Quality-adjusted Life Years?
Authors: Johannesson Magnus , Pliskin Joseph S. , Weinstein Milton C.
Published: March 2007

The construct of the healthy-years equivalent (HYE) has been proposed as an alternative to the quality-adjusted life year (QALY) on the grounds that it avoids certain restrictive assumptions about preferences and also incorporates attitudes toward risk. The authors review the construct of the QALY, including both the commonly used risk-neutral formulation and the more general formulation that permits risk aversion (or risk preference) with respect to remaining life years. They show that the HYE adds flexibility to the risk-neutral form of the QALY by permitting the rate of tradeoff between life years and quality of life to depend on the life span, albeit at the cost of eliciting numerous additional time-tradeoff assessments. However, the claim that the HYE incorporates attitudes toward risk is incorrect, and the proposed two-stage procedure to measure HYEs is neither necessary nor sufficient to in corporate attitudes toward risk. In fact, the HYE assumes risk neutrality with respect to healthy years of life and, therefore, is less suitable for decisions under uncertainty than is the general (risk-averse) form of the QALY. Key words: quality-adjusted life years; healthy- years equivalents; economic evaluation; medical decision making; individual preferences; time-tradeoff; standard gamble; utility theory. (Med Decis Making 1993;13:281-286)
Practice Variation in the Management of Pharyngitis
Authors: Poses Roy M. , Wigton Robert S. , Cebul Randall D. , Centor Robert M. , Collins Marjeanne , Fleischli Gerald J.
Published: March 2007

The objective of this study was to assess whether geographic differences in antibiotic- prescribing rates for patients with pharyngitis could be explained by intersite differences in patients' clinical characteristics and in how physicians responded to these clinical cues when making decisions. As part of the initial phase of a prospective controlled trial to improve physicians' diagnostic ability, the authors enrolled cohorts of consecutive patients seen at staff-model-HMO student health services in Pennsylvania and Nebraska. Physicians' de cisions whether to prescribe antibiotics for 310 consecutive patients presenting with phar yngitis to the former and 214 such patients presenting to the latter at the time of the initial visit were examined. There was a large discrepancy between the antibiotic-prescribing rates at the student health services in Pennsylvania, 106/310, 32.4%, and Nebraska, 156/214, 72.9%. The clinical variables significantly independently associated with treatment at both sites in a logistic regression model were fever, adjusted odds ratio = 2.1 (95% Cl = 1.1, 3.8); exudates, 5.4 (2.8, 10); palatine petechiae, 6.5 (1.5, 28); rhinorrhea, 0.46, (0.25, 0.85); and high risk of complications, 3.8 (1.04, 14). There was a significant interaction between site and anterior cervical adenopathy, 5.5 (1.6, 19); and a borderline interaction between site and rhinorrhea, 2.4 (0.89, 6.7). Site was not a significant independent predictor of treatment, 1.8 (0.45, 6.6.). Practice variation was related to geographic differences in patients' clinical characteristics and in how physicians responded to these factors when prescribing antibiotics. How physicians weight patients' clinical characteristics when making decisions may be an important element of their "practice styles." Key words: geographic variation; prescription decisions; physicians' practice styles; pharyngitis. (Med Decis Making 1993;13:293-301)
Estimating Diagnostic Accuracy from Multiple Conflicting Reports
Authors: Littenberg Benjamin , Moses Lincoln E.
Published: March 2007

Reports of diagnostic accuracy often differ. The authors present a method to summarize disparate reports that uses a logistic transformation and linear regression to produce a summary receiver operating characteristic curve. The curve is useful for summarizing a body of diagnostic accuracy literature, comparing technologies, detecting outliers, and finding the optimum operating point of the test. Examples from clinical chemistry and diagnostic radiology are provided. By extending the logic of meta-analysis to diagnostic testing, the method provides a new tool for technology assessment. Key words: meta-analysis; sensitivity and specificity; decision support; data interpretation, statistical; regression analysis; diagnostic accuracy. (Med Decis Making 1993;13:313-321)
Omission Bias and Pertussis Vaccination
Authors: Asch David A. , Baron Jonathan , Hershey John C. , Kunreuther Howard , Meszaros Jacqueline , Ritov Ilana , Spranca Mark
Published: March 2007

Background: Several laboratory studies have suggested that many people favor potentially harmful omissions over less harmful acts. The authors studied the role of this omission bias in parents' decisions whether to vaccinate their children against pertussis. Methods: Two hundred mail surveys were sent to subscribers to a magazine that had published articles favoring and opposing pertussis vaccination. Subjects were asked about their beliefs about the vaccine and the disease, and whether they had vaccinated their own children or planned to, and they were given test items to identify omission bias in their reasoning. Results: One hundred and three subjects (52%) responded to the survey. Respondents who reported they did not or would not allow their children to be vaccinated (n = 43; 41 %) were more likely to believe that vaccinating was more dangerous than not vaccinating (p < 0.001 ). They were also more likely to exhibit omission bias (p = 0.004), holding constant their stated beliefs about the danger of the vaccine. Conclusions: Omission bias plays a role in decisions not to vaccinate with pertussis vaccine, beyond the role played by belief about the risk of vaccination. Key words: behavioral sciences; decision making; decision theory; ethics; health policy; judgment; pertussis vaccine; probability; psychology; public health; risk; vaccination; whooping cough. (Med Decis Making 1994;14:118-123)