bluuebunny/crossref_metadata_2025 huggingface dataset:
Decision-making Strategies for Telephone Triage in Emergency Medical Services
Authors: Leprohon Judith , Patel Vimla L.
Published: March 2007

Decision-making strategies used by nurses in telephone triage involving public emergency calls for medical help were investigated as a function of task urgency and complexity in the real-world dynamic environment. The sample included 34 nurses as call receivers. Tran scripts of 50 nurse-client dialogues and 50 explanations of the decision-making process, elicited immediately after completion of the calls, were analyzed using methods of discourse and protocol analyses. In high-urgency situations, heuristic rules based on symptoms were used, and the decisions were mostly accurate. With the increase in problem complexity, more causal explanations were found, and the decisions were more often inaccurate. Fur thermore, the explanations supporting the accurate decisions were often inaccurate, showing a decoupling of knowledge and action. Alternate strategies were used in moderate- to low- urgency conditions, where contextual knowledge of the situations was exploited to identify the needs of the clients and to negotiate the best plan of action to meet these needs, resulting in more accurate decisions. Key words: clinical reasoning; cognitive models; context; decision making strategies; emergency medical services; intuition; nursing decision making; telephone triage; uncertainty. (Med Decis Making 1995;15:240-253)
Ethical and Scientific Features of Cutoff-based Designs of Clinical Trials
Authors: Cappelleri Joseph C. , Trochim William M.K.
Published: March 2007

Cutoff-based clinical trial designs are geared towards balancing ethical and scientific con cerns when it is deemed unethical or infeasible to randomize all patients to study treatments. In a cutoff-based design with randomization, patients who are the least sick based on a quantitative baseline indicator are assigned the control treatment, patients who are the most sick based on the same indicator are assigned to test treatment, and patients who are moderately sick based on the indicator are randomly assigned. Simulations were conducted to examine statistical efficiency and potential bias for designs with varying amounts of cutoff- based assignment and randomization. All design variations yielded unbiased estimates of a main treatment effect and a linear interaction effect. While randomization tends to lead to greater efficiency (or lower standard errors of treatment effect), the correlation between the binary treatment variable and baseline assignment variable completely determines the ef ficiency of a design. Key words: clinical trials; randomized control trials; randomization; cutoff- based designs; experimental designs; quasi-experimental designs; methodology; statistical efficiency; bias. (Med Decis Making 1995;15:387-394)
Is Expected Utility Theory Normative for Medical Decision Making?
Authors: Cohen Brian J.
Published: March 2007

Expected utility theory is felt by its proponents to be a normative theory of decision making under uncertainty. The theory starts with some simple axioms that are held to be rules that any rational person would follow It can be shown that if one adheres to these axioms, a numerical quantity, generally referred to as utility, can be assigned to each possible outcome, with the preferred course of action being that which has the highest expected utility. One of these axioms, the independence principle, is controversial, and is frequently violated in experimental situations. Proponents of the theory hold that these violations are irrational The independence principle is simply an axiom dictating consistency among preferences, in that it dictates that a rational agent should hold a specified preference given another stated preference. When applied to preferences between lotteries, the independence principle can be demonstrated to be a rule that is followed only when preferences are formed in a particular way. The logic of expected utility theory is that this demonstration proves that preferences should be formed in this way An alternative interpretation is that this demonstrates that the independence principle is not a valid general rule of consistency, but in particular, is a rule that must be followed if one is to consistently apply the decision rule "choose the lottery that has the highest expected utility." This decision rule must be justified on its own terms as a valid rule of rationality by demonstration that violation would lead to decisions that conflict with the decision maker's goals This rule does not appear to be suitable for medical decisions because often these are one-time decisions in which expectation, a long-run property of a random variable, would not seem to be applicable. This is particularly true for those decisions involving a non-trivial risk of death Key words. expected utility theory, von Neumann-Morgenstern utility, strength of preference; decision analysis; independence principle. (Med Decis Making 1996;16:1-6)
Eccentric Diagnostic Tests
Authors: Somoza Eugene
Published: March 2007

Diagnostic tests exist for which the current definitions of sensitivity and specificity are in adequate. Such tests are called eccentric to distinguish them from normal diagnostic tests, for which the standard definitions are satisfactory. It is shown that when the standard defi nitions are used with eccentric tests there will be an appreciable range of cutoff values over which the test has no discriminating power. This is demonstrated with ROC analysis and information theory New definitions of sensitivity and specificity that are valid for both normal and eccentric tests are proposed. These definitions require the use of two cutoffs to distin guish test-positive from test-negative individuals When the new definitions are used with eccentric tests, performance improves significantly and the anomalous regions of zero dis criminating power disappear. In the limit of zero eccentricity the new definitions become identical to the old. Key words: eccentric diagnostic tests; sensitivity; specificity, ROC anal ysis ; information theory. (Med Decis Making 1996;16:15-23)
The College Student, the Dentist, and the North Carolina Senator
Authors: Robinson Edward N. , De Bliek Ruth
Published: March 2007

The risk of acquiring human immunodeficiency virus (HIV) infection from a health care worker is 2,000 times less than that of dying from a car accident. It is 700 times less probable than perishing from being struck by lightning or suffering a fatal fall. Despite the rarity of this occurrence, reduction of the risk of health-care-worker-to-patient HIV transmission in the workplace has been the focus of congressional, federal, state, and local agencies. If all HIV transmission from health care workers to patients were prevented using current guidelines and legislation, the epidemic of AIDS would be reduced by 0.0006% Current efforts to prevent HIV transmission from health care workers to patients are the result of incomplete risk analysis and management. In a society of limiting resources and of cherished freedoms, sanctions imposed on health care workers to prevent HIV transmission to patients may benefit no one. Key words: HIV; risk analysis; risk management; policy. (Med Decis Making 1996;16:86-91)
Oregon's Medicaid Ranking and Cost- Effectiveness
Authors: Tengs Tammy O. , Meyer Gregg , Siegel Joanna E. , Pliskin Joseph S. , Graham John D. , Weinstein Milton C.
Published: March 2007

The authors examine whether Oregon's 1990, 1991, 1992, and 1993 prioritized lists were ranked in a manner consistent with cost-effectiveness. Two sets of cost-ef fectiveness data are used: data from economic analyses and Oregon's own cost- effectiveness data. Comparing the ranks of Oregon's lists with the ranks of cost- effectiveness estimates from the literature reveals Spearman correlations of -0.08 for the 1990 list, +0.39 for the 1991 list, +0.25 for the 1992 list, and +0.24 for the 1993 list. Comparing Oregon's lists with Oregon's own cost-effectiveness data reveals rank correlations of +0.99 for the 1990 list, +0.06 for the 1991 list, -0.05 for the 1992 list, and -0.03 for the 1993 list. Thus, there appear to be essentially no relationship be tween the 1990 list and cost-effectiveness estimates from the economic literature and modest positive relationships between the 1991-93 lists and the literature. In addition, there is virtually no relationship between the 1991-93 lists and Oregon's own cost- effectiveness data. Further, the correlations are very different from +1.0, suggesting that other factors are at play. For example, the 1993 list that is currently being imple mented was ranked primarily by improvement in five-year survival and human judg ment, not cost-effectiveness. Key words: Oregon; Medicaid; cost-effectiveness; ra tioning ; resource allocation. (Med Decis Making 1996;16:99-107)
Decision Making with Respect to Diagnostic Testing
Authors: Cairns John , Shackley Phil , Hundley Vanora
Published: March 2007

This paper outlines a model for valuing the benefits of antenatal screening based on the analysis of individual decision making with respect to consequent diagnostic test ing. Central to the model is the idea that the benefits of screening can be measured by valuing the improved information generated from screening. The model is developed in the context of antenatal carrier screening for cystic fibrosis (CF). Benefits are as sessed by surveying women in the general population in order to establish their pref erences for two alternative methods of CF carrier screening—stepwise and couple screening. Preferences are elicited using standard-gamble questions in which women from a population-based random sample are asked to trade off risk of fetal loss with improved information from diagnostic testing. A series of standard-gamble questions is employed to elicit utility values for each of the possible information outcomes from screening. The expected utilities of both screening methods are calculated at both individual and group levels. The results suggest that the use of individual decision making with respect to diagnostic testing as a means of valuing the benefits of screen ing may have wide applications. Key words: benefits; antenatal screening; information; standard gamble; expected utility. (Med Decis Making 1996;16:161-168)
Angina Patients' Ratings of Current Health and Health without Angina
Authors: Chen Arnold Y. , Daley Jennifer , Thibault George E.
Published: March 2007

Objective. To investigate the relationship between chronic stable angina patients' rat ings of two health states (current health and health free of angina), the difference between these two ratings (the "anticipated gain"), and measures of anginal severity and comorbidity. Design. Cross-sectional interviews and questionnaires. Setting. Out patient clinics and medical inpatient service of a Veterans Affairs Medical Center. Par ticipants. Patients with chronic stable angina with no prior history of a revascularization procedure attending clinic appointments (n = 44) or electively admitted for cardiac catheterization (n = 11). Measurements. Ratings of current health and health free of angina using a verbal rating scale in which 0 = death and 100 = perfect health, the MOS SF-36, the Index of Coexistent Disease (a validated measure of comorbidity), and a question on the severity of anginal symptoms. Results. Mean (95% Cl) rating of current health was 61.8 (59.2, 64.4) and that of health free of angina was 77.0 (74.5, 79.5). Median anticipated gain between the two health ratings was 10.0 (range 0-80). Correlations between ratings for both health states and subscales of the SF-36 were positive, with some reaching statistical significance. In regression models with rating of current health, rating of life without angina, and anticipated gain as the dependent variables, severity of comorbidity was highly significant in all three, whereas severity of angina was significant only in the current-health rating model. Severity of comorbidity had much greater explanatory power in all three models than did severity of angina. Conclusions. Severity of comorbidity was a better predictor of patients' current health rating, rating for angina-free health, and anticipated gain from relief of angina than was severity of angina. Since patient perceptions of a symptom may be distinct from self- reported symptom severity, treatment-outcome studies should assess patient prefer ences in addition to symptom severity. Comorbidity should also be measured in such studies. Having patients rate current health and symptom-free health may be a useful measure of treatment effectiveness for specific symptoms in clinical trials and patient care, and may help patients and clinicians prioritize multiple health problems. Key words: quality of life; functional status; utility; patient preferences; comorbidity; angina. (Med Decis Making 1996;16:169-177)
Sequential Test Selection in the Analysis of Abdominal Pain
Authors: Castro Frank , Caccamo Leonard P. , Carter Kimbroe J. , Erickson Barbara A. , Johnson William , Kessler Edward , Ritchey Nathan P. , Ruiz Claudio A.
Published: March 2007

Numerous decision-making tools exist to assist physicians in diagnosis management. However, the accuracy of available clinical information is often ambiguous or unknown and current analytical models do not explicitly incorporate judgmentally defined infor mation. A model encompassing both physician judgment and probability analysis was developed to accommodate such data. A problem requiring sequential diagnostic test ing was structured utilizing the analytic hierarchy process (AHP). The case presented involved a patient complaining of upper abdominal pain who, after initial evaluation, did not need immediate surgery. Physicians were faced with identifying the optimal sequence of diagnostic testing. The criteria used for test selection included minimizing risk, patient discomfort, and cost of testing and maximizing diagnostic capability. Al though at the onset the "best" test choice was unknown, the clinical picture indicated four test alternatives: upper gastrointestinal series (GI), abdominal ultrasonography (US), abdominal computed tomography (CT), and upper gastrointestinal endoscopy (END). Based upon the relative preferences of the criteria utilized, the AHP analysis indicated that upper GI series was the optimal first test. Given a negative test, posterior probabilities were calculated using Bayes' theorem, resulting in a new estimate of diagnostic capability. The AHP analysis was reiterated, identifying abdominal ultraso nography as the optimal second test. This analysis may be repeated as many times as necessary. Sensitivity analysis demonstrated that changing criteria preferences may alter the choice of tests and/or their sequence. Key words: analytic hierarchy process (AHP); Bayes' theorem; test sequence; diagnosis; sensitivity analysis. (Med Decis Making 1996;16:178-183)
Willingness to Pay for Reductions in Angina Pectoris Attacks
Authors: Kartman Bernt , Andersson Fredrik , Johannesson Magnus
Published: March 2007

To compare the costs of health care programs with the benefits, the values of changes in health status must be expressed in monetary terms. The development of methods to estimate willingness to pay for changes in health status is therefore of interest. This paper reports the results of a contingent valuation study measuring willingness to pay for reductions in angina pectoris attacks. An innovative study design allowed analysis of the data on willingness to pay using two approaches, a binary question and a bid ding-game technique. Percentage reductions in anginal attacks were varied randomly in different subsamples, and data were collected about angina pectoris status, attack rate, and income to test the internal validity of the contingent valuation method. Will ingness to pay for a 50% reduction in the attack rate for three months was estimated to be about SEK 2,500 ($345) with the binary approach, and about SEK 2,100 ($290) using the bidding-game technique. Regression analyses showed that income, angina pectoris status, attack rate, and percentage reduction in attack rate were all related to willingness to pay, in agreement with the authors' hypothesis. Key words: willingness to pay; contingent valuation; angina pectoris; cost-benefit analysis. (Med Decis Mak ing 1996;16:248-253)
How Convergence of Research Paradigms Can Improve Research on Diagnostic Judgment
Authors: Hammond Kenneth R.
Published: March 2007

The author's purpose is to urge the constructive convergence of two current judgment and decision-making research paradigms. He shows why the heuristics-and-biases approach and the lens-model approach should be placed in the context of two very different metatheories, the coherence metatheory and the correspondence metatheory. The differences between the two research paradigms thus become apparent; they speak to different problems and appeal to different criteria for evaluating performance. Bringing the two into a constructive relationship to one another, however, will not only double the store of knowledge regarding diagnostic judgment and decision making, but also enhance efforts to achieve a cumulative discipline. Isolating these research paradigms from one another—as is done now—stifles theoretical generality, frag ments knowledge, and confuses medical decision makers. An example of how con vergence can be achieved is provided. Key words: diagnostic judgment; Bayes' the orem ; lens model. (Med Decis Making 1996;16:281-287)
A Cost Analysis of the Prevention of End-stage Renal Disease
Authors: Durand-Zaleski Isabelle , Bastuji-Garin Sylvie , Zaleski Stéphane , Weil Bertrand , Rostoker Guy
Published: March 2007

A cost analysis was used to evaluate three possible immunoglobulin (IgG) treatment protocols for end-stage renal disease due to IgA nephropathy. The perspective chosen for the cost analysis was that of the health-care delivery system. The baseline strategy was the absence of IgG treatment, and alternative strategies corresponded to three protocols presently on trial: all three included a high initial dose of intravenous IgG. Protocol 1 followed with intramuscular IgG injections only, protocol 2 with intramuscular plus intravenous injections, and protocol 3 with intravenous injections only. The costs of treatment included the costs of immunoglobulins, outpatient hospital costs, and the costs of tests; the savings (costs averted) resulted from kidney dialysis averted. The bottom line for the health-care system is a net savings of $233,000, $213,000, or $83,000, depending on the protocol chosen. The computation of costs did not value physical and psychological health benefits. Thus, any subjective benefit, such as im proved comfort, or objective benefit, such as longer life expectancy, would be an im provement over the results presented here. Key words: cost analysis; end-stage renal disease; treatment protocols. (Med Decis Making 1996;16:326-334)
Predicting Quality of Well-being Scores from the SF-36
Authors: Fryback Dennis G. , Lawrence William F. , Martin Patricia A. , Klein Ronald , Klein Barbara E.K.
Published: March 2007

Background. The SF-36 and the Quality of Well-being index (QWB) both quantify health status, yet have very different methodologic etiologies. The authors sought to develop an empirical equation allowing prediction of the QWB from the SF-36. Data. They used empirical observations of SF-36 profiles and QWB scores collected in in terviews of 1,430 persons during the Beaver Dam Health Outcomes Study, a com munity-based population study of health status, and 57 persons from a renal dialysis clinic. Method. The eight scales of the SF-36, their squares, and all pairwise cross- products, were used as candidate variables in stepwise and best-subsets regressions to predict QWB scores using 1,356 interviews reported in a previous paper. The re sulting equation was cross-validated on the remaining 74 cases and using the renal dialysis patients. Results. A six-variable regression equation drawing on five of the SF- 36 components predicted 56.9% of the observed QWB variance. The equation achieved an R2 of 49.5% on cross-validation using Beaver Dam participants and an R2 of 58.7% with the renal dialysis patients. An approximation for computing confidence intervals for predicted QWB mean scores is given. Conclusion. SF-36 data may be used to predict mean QWB scores for groups of patients, and thus may be useful to modelers who are secondary users of health status profile data. The equation may also be used to provide an overall health utility summary score to represent SF-36 profile data so long as the profiles are not severely limited by floor or ceiling effects of the SF-36 scales. The results of this study provide a quantitative link between two important measures of health status. Key words: health status; SF-36; Quality of Well- being index; quality of life; health-state utility; population study. (Med Decis Making 1997;17:1-9
A Method to Elicit Utilities for Interpersonal Comparisons
Authors: Holmes Ann M.
Published: March 2007

This paper examines how values should be assigned to health states when policy decisions must be made about who should receive treatment. The paper demonstrates that, if priority were to be assigned to those people who would benefit most from treatment, standard health-state utilities might fail to identify resource allocations that would maximize total health-related well-being in society. A new measurement instru ment is proposed that is based on the direct comparison of the well-being achieved by different people in various health states and thus captures such community priori ties. A sample of 72 health administration students used the instrument to evaluate speech and mobility dysfunctions as they afflicted hypothetical people who differed by gender, family status, and occupational type. This preliminary analysis indicates that the instrument is feasible to use, and that the valuations of respondents did, for some health conditions, significantly depend on the type of person afflicted. Key words: util ities ; interpersonal comparisons; ethics; health policy; extended-sympathy instrument. (Med Decis Making 1997;17:10-20)
The Influence of Physician Explanations on Patient Preferences about Future Health-care States
Authors: Mazur Dennis J. , Hickam David H.
Published: March 2007

Objective. To determine the influence of alternative explanations by physicians of the purpose of a medical intervention (intubation and ventilatory support, IVS) on three types of patient preferences: desire for IVS, the length of time patients would find IVS acceptable, and the minimum probability of a good medical outcome patients would require before assenting to continued support with IVS. Methods. Structured interviews were conducted with patients followed in a continuity care general medicine clinic at the Department of Veterans Affairs Medical Center, Portland, Oregon. Patients were asked to consider whether they would accept IVS at a future time. Patients were randomly assigned to one of two explanation conditions that differed in terms of their future medical contexts, that is, the degrees of specification of the nature of the medical condition patients were asked to consider. The general-explanation group was asked to consider the future medical context of "an unspecified medical condition"; the spe cific-explanation group was asked to consider the future medical context of "a severe pneumonia." Patients were asked three questions: 1) Would you accept IVS (yes or no)? 2) How long would you allow your physician to continue IVS?; and 3) After being on IVS for 2-3 days, what would be the minimum chance of recovery from the con dition you would require before agreeing to continued IVS? "Chance of recovery" was defined for both groups as the probability that the patient would be able to leave the hospital and be able to take care of activities of daily living unassisted with minimal change in his or her mental state from the pre-hospitalization status. Results. Of 186 patients (mean age = 66.5 years; mean education = 12.7 years), 97 received the general explanation and 89 received the specific explanation about a severe pneu monia. Significantly fewer (p = 0.03) patients receiving the general explanation wanted physicians to intervene with IVS (general 94% vs specific 100%). Patients receiving the general explanation were willing to accept significantly fewer (p = 0.009) days of intubation (general 65 days vs specific 96 days). Significantly fewer (p < 0.0001) pa tients receiving the general explanation wanted physicians to continue IVS when the probability of a successful outcome was less than 50% (general 30% vs specific 64%). Conclusion. Physician explanations—based on general (unspecified medical condi tion) vs specific (severe pneumonia) explanations—have a marked influence on the duration of IVS patients would permit and the probability of a good outcome required to continue IVS. Key words: advance directives; life support; patient preferences; patient-physician decision making. (Med Decis Making 1997;17:56-60)
Determining Transition Probabilities from Mortality Rates and Autopsy Findings
Authors: Black William C. , Nease Robert F. , Welch H. Gilbert
Published: March 2007

The Markov process is a useful tool for modeling the natural history of disease, which is becoming increasingly important as new diagnostic tests increase the detectability of early-stage disease. The accuracy of a Markov model, however, depends on the accuracy of the estimates for the transition probabilities between different stages of disease. Because these estimates are usually based on "expert opinion" or small cohort studies, they are subject to imprecision and bias. The authors describe an alternative method of estimating transition probabilities from the stage distribution of disease observed at the time of death and age-specific mortality rates from other causes. In addition, they prove that the transition probabilities are unique given certain assumptions about how they change with age. Finally, they illustrate the method using population-based data for prostate cancer. Key words: Markov process; transition prob abilities ; cohort studies; selection bias; precision; population-based mortality rates; stage distribution at autopsy. (Med Decis Making 1996;16:87-93)
A Comparison of Parametric and Nonparametric Approaches to ROC Analysis of Quantitative Diagnostic Tests
Authors: Hajian-Tilaki Karim O. , Hanley James A. , Joseph Lawrence , Collet Jean-Paul
Published: March 2007

Receiver operating characteristic (ROC) analysis, which yields indices of accuracy such as the area under the curve (AUC), is increasingly being used to evaluate the performances of diagnostic tests that produce results on continuous scales. Both par ametric and nonparametric ROC approaches are available to assess the discriminant capacity of such tests, but there are no clear guidelines as to the merits of each, particularly with non-binormal data. Investigators may worry that when data are non- Gaussian, estimates of diagnostic accuracy based on a binormal model may be dis torted. The authors conducted a Monte Carlo simulation study to compare the bias and sampling variability in the estimates of the AUCs derived from parametric and nonparametric procedures. Each approach was assessed in data sets generated from various configurations of pairs of overlapping distributions; these included the binormal model and non-binormal pairs of distributions where one or both pair members were mixtures of Gaussian (MG) distributions with different degrees of departures from bi- normality. The biases in the estimates of the AUCs were found to be very small for both parametric and nonparametric procedures. The two approaches yielded very close estimates of the AUCs and of the corresponding sampling variability even when data were generated from non-binormal models. Thus, for a wide range of distributions, concern about bias or imprecision of the estimates of the AUC should not be a major factor in choosing between the nonparametric and parametric approaches. Key words: ROC analysis; quantitative diagnostic test; comparison, parametric; binormal model; LABROC; nonparametric procedure; area under the curve (AUC). (Med Decis Making 1997;17:94-102)
Use of a Probabilistic Neural Network to Estimate the Risk of Mortality after Cardiac Surgery
Authors: Orr Richard K.
Published: March 2007

Objective. To develop a probabilistic neural network (PNN) to estimate mortality risk following cardiac surgery. Design and setting. The PNN model was created using an institutional database obtained as part of routine quality assurance activity. Patient records (from 1991 to 1993) were randomly divided into training (n = 732) and validation (n = 380) sets. The model uses seven variables, each obtainable during routine clinical patient care. After completion of the initial validation phase, newer data (1994) became available and were used as an independent source of validation (n = 365). Patients. 1,477 consecutive cardiac surgery patients operated on in a teaching hospital during a four-year period (1991-94). Results. The overall accuracy of the neural network was 91.5% in the training set; it was 92.3% in the validation set. The model was well calibrated (p = 0.21 for the Hosmer-Lemeshow goodness-of-fit test) and discriminated well (areas under the ROC curves were 0.72 and 0.81 for the training and validation sets). The trained network also performed well on the 1994 data (ROC = 0.74, p = 0.19 for the Hosmer-Lemeshow test), albeit with a slight decrement in overall accuracy (88.2%). Conclusion. A neural network may be implemented to estimate mortality risk following cardiac surgery. Implementation is relatively rapid, and it is an alternative to standard statistical approaches. Key words: neural networks; cardiac surgery; predictive models. (Med Decis Making 1997;17:178-185)
Guidelines for Verbal Presentations of Medical Decision Analyses
Authors: Redelmeier Donald A. , Detsky Allan S. , Krahn Murray D. , Naimark David , Naglie Gary
Published: March 2007

Individuals new to decision analysis often have difficulty with oral presentations of original research projects. This article provides general guidelines on how to present effectively. Points include: 1) articulating the research issue, 2) reviewing current beliefs, 3) portraying the study question, 4) listing the main assumptions, 5) presenting the base-case analysis, 6) showing sensitivity analyses, and 7) discussing the implications. The guidelines comment on what to exclude from presentation and how best to handle audience questions. The guidelines do not replace general instruction in public speaking (or rigorous training in decision analysis), but may help students present research projects effectively. Key words: decision analysis; verbal presentations; medical education; public speaking; communication skills. (Med Decis Making 1997; 17:228-230)
Cost-Effectiveness of Repeat Medical Procedures
Authors: Hornberger John C. , Best Jennie H. , Garrison Louis P.
Published: March 2007

The constraints on medical-care resources can give rise to the question of the cost- effectiveness of permitting repeat medical procedures when some patients may die without undergoing even a first procedure. Using kidney transplantation as an example, this study estimates the cost-effectiveness of patients' having available the option of a repeat medical procedure in the event the first procedure fails. Specifically, the anal ysis examines the effect on transplant candidates of having the option of kidney re transplantation, if and when retransplantation might be needed. Data sources include the U.S. Renal Data System (USRDS) Case-Mix Severity Study, Health Care Financ ing Administration (HCFA) data, and a MEDLINE search. Outcome measures include life expectancy, quality-adjusted life expectancy, lifetime costs of medical care, and mar ginal cost-effectiveness from a societal perspective. By avoiding lifelong dialysis after graft failure, first-transplant candidates gain an average of 47 quality-adjusted days with a retransplantation policy, despite the prolongation of time to first transplant by an average of 30 quality-adjusted days. The lifetime cost of medical care per first- transplant candidate is $1,210 higher with a retransplantation policy compared with the no-retransplantation policy; its societal cost-effectiveness is estimated to be $9,656 per quality-adjusted life-year saved. The retransplantation policy provides the greatest improvement in quality-adjusted life expectancy for younger candidates. In the case of kidney transplantation, the cost-effectiveness of a repeat transplant, on average, com pares favorably with those of other medical strategies in common practice. As re sources become increasingly constrained, this study demonstrates a framework for considering the cost-effectiveness of repeat medical procedures. Key words: kidney transplantation; decision analysis; cost-effectiveness analysis; ethics; rationing. (Med Decis Making 1997;17:363-372))
Assessing Uncertainty in Cost-Effectiveness Analyses
Authors: Parmigiani Giovanni , Samsa Greg P. , Ancukiewicz Marek , Lipscomb Joseph , Hasselblad Vic , Matchar David B.
Published: March 2007

A framework for quantifying uncertainty about costs, effectiveness measures, and mar ginal cost-effectiveness ratios in complex decision models is presented. This type of application requires special techniques because of the multiple sources of information and the model-based combination of data. The authors discuss two alternative ap proaches, one based on Bayesian inference and the other on resampling. While com putationally intensive, these are flexible in handling complex distributional assumptions and a variety of outcome measures of interest. These concepts are illustrated using a simplified model. Then the extension to a complex decision model using the stroke- prevention policy model is described. Key words: cost-effectiveness analysis; sto chastic models; decision analysis; simulation; stroke; cerebrovascular disease. (Med Decis Making 1997;17:390-401)
A Normative Analytic Framework for Development of Practice Guidelines for Specific Clinical Populations
Authors: Owens Douglas K. , Nease Robert F.
Published: March 2007

Background. A central problem in practice guideline development is how to develop guidelines that appropriately account for variations in clinical populations and practice settings. Despite recognition of this problem, there is no formal mechanism for as sessing what the need is for flexibility in guidelines, or for deciding how to incorporate such flexibility into recommendations. Objective. This research sought to provide a formal basis to determine when clinical circumstances vary sufficiently that guideline recommendations should differ, how recommendations should be tailored for a specific clinical setting, and whether the benefit associated with such site-specific guidelines justifies the expense of their development. Results. The authors describe an approach for estimating the maximum health benefit that developers can obtain by eliminating uncertainty about differences in the patient populations and practice settings in which a guideline will be used. This estimate, the expected value of customization, provides a mechanism to evaluate the cost-effectiveness of the development of site-specific guidelines that account explicitly for variation in clinical circumstances. Application of this method to the development of screening guidelines for human immunodeficiency virus (HIV) infection indicates that the development of site-specific guidelines poten tially is cost-effective. Site-specific guidelines either improve, or leave unchanged, the efficiency of HIV screening; whether they increase or decrease total expenditures and health benefits depends on the choice of a cost-effectiveness threshold, and the clin ical problem. Conclusions. Development of guideline recommendations based on de cision models provides a normative approach for evaluating the need for and the cost-effectiveness of site-specific guidelines that have been tailored to specific prac tice settings. Such site-specific guidelines can improve substantially the expected health benefit and the economic efficiency of practice guidelines. Key words: practice guidelines; decision models; cost-effectiveness; site-specific guidelines. (Med Decis Making 1997;17:409-426)
Application of Treatment Thresholds to Diagnostic-test Evaluation
Authors: Moons Karel G.M. , Stijnen Theo , Michel Bowine C. , Büller Harry R. , Van Es Gerrit-Anne , Grobbee Diederick E. , Habbema J. Dik F.
Published: March 2007

Diagnostic tests are often evaluated by comparison of the areas under receiver op erating charactenstic (ROC) curves. In this study the authors compared this approach with a more direct method that takes into account consequences of a diagnosis. Data from a prospective study of diagnosis of pulmonary embolism were used for a moti vating example. Using multivariable logistic regression analysis, three diagnostic mod els were built and compared based on their ROC curves. Although model 1 (0.706) and model 2 (0.702) had the same ROC-curve area, they performed differently when risks and benefits of subsequent decisions were considered by applying the treatment probability threshold. Models 1 and 3 (0.611) had substantially different ROC-curve areas but performed similarly taking into account the therapeutic consequences. This demonstrates that comparison of diagnostic tests using the areas under the ROC curves may lead to erroneous conclusions about therapeutic usefulness. To corre spond to daily practice, it would be more appropriate to also consider the clinical im plications in evaluating diagnostic tests. This is made feasible by explicit definition and application of a treatment threshold. Key words: benefits and risks; clinical relevance; diagnosis; diagnostic test evaluation; ROC curve; treatment threshold. (Med Decis Making 1997;17:447-454)
Patient Preferences for Thrombolytic Therapy in Acute Myocardial Infarction
Authors: Stanek Eric J. , Cheng Judy W.M. , Peeples Patricia J. , Simko Robert J. , Spinler Sarah A.
Published: March 2007

Background. Despite extensive professional debate regarding the optimal thrombolytic therapy strategy in acute myocardial infarction (AMI), patient preferences have not been explored. Methods. Preferences among patients with known or suspected coro nary artery disease for treatment with tissue plasminogen activator (tPA) or streptoki nase (SK) for AMI were determined using a questionnaire presenting GUSTO-1 trial and drug cost data. Preferences were based on consideration of 30-day mortality (M) alone, hemorrhagic stroke rate (SR) alone, overall preference (M + SR), drug acqui sition costs, and the estimated annual costs of using a single agent to treat all AMIs. Cost-related responses were provided under payer designations of self, third-party insurance, and federal government. Results. The response rate was 81% (101/125 patients). tPA was preferred by 84%, and SK by 66%, for M alone and SR alone, respectively (χ 2, p < 0.01). Overall preference (M + SR) favored tPA (78%, p < 0.01). tPA preference decreased to 43% considering drug acquisition costs under the self- pay option (p < 0.01 vs M + SR). Similar trends of lesser magnitude were also ob served for the third-party and government-payer options. Conclusions. Under condi tions of zero cost and consideration of mortality plus stroke-risk data, tPA was preferred overall due to its lower mortality. Introduction of drug-cost data significantly shifted the preference toward SK, particularly under the self-payer designation. Patient prefer ences for thrombolytic therapy in AMI indicate tradeoffs between clinical attributes and cost, and should assist in framing medical debate and decision making. Key words: patient preferences; thrombolytic therapy; acute myocardial infarction; streptokinase; tissue plasminogen activator. (Med Decis Making 1997;17:464-471)
The Cost-Effectiveness of HIV Testing
Authors: Paltiel A. David , Kaplan Edward H.
Published: March 2007

Objective. To understand the impact of differences in participation rates between in fected and uninfected individuals on estimates of the cost-effectiveness of HIV screening. Methods. Costs per infection detected are modeled as function of both prevalence and serostatus-dependent testing rates. Data from national surveillance surveys, seroprevalence studies, and other sources are employed to suggest the mag nitude of results. Results. Differential participation produces a near-doubling in the estimated cost per infection identified. This result is sensitive to assumptions regarding the benefits of screening for seronegatives. Conclusions. Voluntary HIV screening pro grams may incur prohibitive costs by over-recruiting people at little risk of infection. Failure to account for differential participation can result in over-optimistic cost-ef fectiveness estimates. However, the relevance of this result—and the significance of both prevalence and participation as cost drivers—is overwhelmed by what is as sumed about the benefits conferred to uninfected people by HIV screening. Key words: cost-effectiveness analysis; HIV testing; policy modeling. (Med Decis Making 1997;17:490-495)
Is the Defensive Use of Diagnostic Tests Good for Patients, or Bad?
Authors: DeKay Michael L. , Asch David A.
Published: March 2007

Physicians sometimes order diagnostic tests to reduce the risk of malpractice liability. The authors develop an expected-utility model that links a rational physician's concerns about malpractice liability to increases in the use of diagnostic tests and use this model to assess the effects of defensive testing on patients' interests. To do so, they adapt the threshold approach to clinical decision making to incorporate the physician's inter ests, focusing on 1) the effect of the physician's expected liability risks and 2) the effect of any expected liability reduction due to diagnostic testing. Surprisingly, the mere existence of liability risks is often sufficient to widen the range of disease probabilities for which diagnostic testing is the preferred clinical strategy. If testing reduces the physician's expected liability risks, the testing range is widened further. For some dis ease probabilities, testing is preferred by the physician even though it is not in the patient's best interests. When tests are performed in such instances, utility is trans ferred from the patient to the physician and the physician's insurer. Although the de fensive use of diagnostic tests improves clinical outcomes for some patients, it worsens clinical outcomes for others. Moreover, defensive testing worsens the expected out comes of all patients whose clinical strategies are changed. Physicians should realize that defensive testing necessarily reduces the overall quality of patient care. Key words: decision analysis; decision threshold; defensive medicine; diagnostic testing; expected utility; malpractice liability. (Med Decis Making 1998;18:19-28)
Fitting Multistate Transition Models with Autoregressive Logistic Regression
Authors: de Vries Sybolt O. , Fidler Vaclav , Kuipers Wietze D. , Hunink Maria G.M.
Published: March 2007

The purpose of this study was to develop a model that predicts the outcome of su pervised exercise for intermittent claudication. The authors present an example of the use of autoregressive logistic regression for modeling observed longitudinal data. Data were collected from 329 participants in a six-month exercise program. The levels of the polytomous outcome variable correspond to states they defined in a Markov de cision model comparing treatment strategies for intermittent claudication. Autoregres sive logistic regression can be used to fit multistate transition models to observed longitudinal data with standard statistical software. The technique allows exploration of alternative assumptions about the dependence in the outcome series and provides transition probabilities for different covariate patterns. Of the alternatives examined, a Markov model including two preceding responses, time, age, ankle brachial index, and duration of disease best described the data. Key words: longitudinal data analysis; autoregressive models; logistic regression; Markov models; peripheral arterial occlu sive disease; intermittent claudication; exercise. (Med Decis Making 1998;18:52- 60)
Sensitivity Analysis and the Expected Value of Perfect Information
Authors: Felli James C. , Hazen Gordon B.
Published: March 2007

Measures of decision sensitivity that have been applied to medical decision problems were examined. Traditional threshold proximity methods have recently been supple mented by probabilistic sensitivity analysis, and by entropy-based measures of sen sitivity. The authors propose a fourth measure based upon the expected value of perfect information (EVPI), which they believe superior both methodologically and prag matically. Both the traditional and the newly suggested sensitivity measures focus en tirely on the likelihood of decision change without attention to corresponding changes in payoff, which are often small. Consequently, these measures can dramatically over state problem sensitivity. EVPI, on the other hand, incorporates both the probability of a decision change and the marginal benefit of such a change into a single measure, and therefore provides a superior picture of problem sensitivity. To lend support to this contention, the authors revisit three problems from the literature and compare the results of sensitivity analyses using probabilistic, entropy-based, and EVPI-based mea sures. Key words: sensitivity analysis; expected value of perfect information. (Med Decis Making 1998;18:95-109)
Statistical Comparison of Two ROC-curve Estimates Obtained from Partially-paired Datasets
Authors: Metz Charles E. , Herman Benjamin A. , Roe Cheryl A.
Published: March 2007

The authors propose a new generalized method for ROC-curve fitting and statistical testing that allows researchers to utilize all of the data collected in an experimental comparison of two diagnostic modalities, even if some patients have not been studied with both modalities. Their new algorithm, ROCKIT, subsumes previous algorithms as special cases. It conducts all analyses available from previous ROC software and provides 95% confidence intervals for all estimates. ROCKIT was tested on more than half a million computer-simulated datasets of various sizes and configurations repre senting a range of population ROC curves. The algorithm successfully converged for more than 99.8% of all datasets studied. The type I error rates of the new algorithm's statistical test for differences in Az estimates were excellent for datasets typically en countered in practice, but diverged from alpha for datasets arising from some extreme situations. Key words. receiver operating characteristic (ROC) analysis, maximum-like lihood estimation; partially-paired data; missing data. (Med Decis Making 1998;18: 110-121)