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D K Owens

Publications and source records attributed to D K Owens.

At least 19 recordsLinked to original sources
PubMed1998

Population effects of preventive and therapeutic HIV vaccines in early- and late-stage epidemics.

OBJECTIVE: To evaluate the population effects of potential preventive and therapeutic vaccines in early- and late-stage epidemics in a population of homosexual men. METHODS: An epidemic model was used that simulated the course of the epidemic for a population of homosexual men in San Francisco, California. Vaccine programs were evaluated by the number of cases of HIV averted, the effect on the prevalence of HIV, and by the gain in quality-adjusted life years (QALY) for the total population. RESULTS: In the model, a preventive vaccine prevented 3877 cases of HIV infection during a 20-year period, reduced the projected prevalence of HIV infection from 12 to 7% in a late-stage epidemic, and gained 15,908 QALY. A therapeutic vaccine that did not affect the infectivity of vaccine recipients increased the number of cases of HIV infection by 210, resulted in a slight increase in the prevalence of HIV infection from 12 to 15% in a late-stage epidemic, and gained 8854 QALY. If therapeutic vaccines reduced infectivity, their use could produce net gains of QALY in the population that were similar to gains from the use of preventive vaccines. In an early-stage epidemic, the advantage of a preventive vaccine program relative to a therapeutic vaccine program was markedly enhanced. CONCLUSIONS: Both preventive and therapeutic vaccine programs provided substantial benefit, but their relative merit depended on which outcome measures were assessed. Evaluation of HIV vaccine programs based solely on cases averted or on prevalence of HIV in the population underestimates the benefit associated with therapeutic vaccine programs. The effect of a therapeutic HIV vaccine on the epidemic outcomes depended markedly on whether the therapeutic vaccine reduced the infectivity of the vaccine recipient. The relative merits of preventive and therapeutic vaccines depend on the stage of the epidemic. Field vaccine trials should evaluate correlates of infectivity, such as HIV viral load. HIV vaccine implementation strategies should be tailored to the dynamics of the epidemic in specific populations.

AIDS Vaccines↗
PubMed1998

Spine update. Patient preferences and the development of practice guidelines.

One shortcoming of clinical practice guidelines is that generic, one-for-all guideline recommendations do not account for differences among patients' views about the desirability (or undesirability) of specific health outcomes, such as low back pain. Because differences in patients' preferences may lead to differences in the preferred therapy, a clinical practice guideline that does not consider patients' preferences may provide recommendations that are not optimal. Recently developed methodologic approaches enable guideline developers to assess the role of patients' preferences in clinical decisions and guideline recommendations, and to develop preference-based guidelines. Preference-based guidelines are more likely to meet criteria for high-quality guidelines than are guidelines developed without consideration of the role of patients' preferences. Guideline developers should identify decisions in which patient preferences are important and note these decisions clearly in the written guideline; indicate the specific health states for which preferences are important; and, if possible, provide recommendations about options for preference assessment. These options range from informal discussions with patients to computer-based utility assessments. Patients' preferences are an important factor in clinical decisions regarding management of low-back pain, particularly in decisions about surgical management and symptom control. Although further research is needed to define the role of techniques for assessing patients' preferences in routine clinical practice, guideline developers can determine when patients' preferences should play a prominent role in guideline recommendations.

Decision Making↗
PubMed1998

Cost-effectiveness of preference-based antithrombotic therapy for patients with nonvalvular atrial fibrillation.

BACKGROUND AND PURPOSE: Recent atrial fibrillation guidelines recommend the incorporation of patient preferences into the selection of antithrombotic therapy. However, no trial has examined how incorporating such preferences would affect quality-adjusted survival or medical expenditure. We compared 10-year projections of quality-adjusted survival and medical expenditure associated with two atrial fibrillation treatment strategies: warfarin-for-all therapy versus preference-based therapy. The preference-based strategy prescribed whichever antithrombotic therapy, warfarin or aspirin, had the greater projected quality-adjusted survival. METHODS: We used decision analysis stratified by the number of stroke risk factors (history of stroke, transient ischemic attack, hypertension, diabetes, or heart disease). The base case focused on compliant 65-year-old patients who had nonvalvular atrial fibrillation and no contraindications to antithrombotic therapy. RESULTS: In patients whose only risk factor for stroke was atrial fibrillation, preference-based therapy improved projected quality-adjusted survival by 0.05 quality-adjusted life year (QALY) and saved $670. For patients who had atrial fibrillation and one additional risk factor for stroke, preference-based therapy improved quality-adjusted survival by 0.02 QALY and saved $90. In patients who had atrial fibrillation and multiple additional risk factors for stroke, preference-based therapy increased medical expenditures and did not improve quality-adjusted survival substantially. The benefits of preference-flexible therapy arose from the minority of patients who would have had a longer quality-adjusted survival if they had been prescribed aspirin rather than warfarin. CONCLUSIONS: As do risks of stroke and of hemorrhage, patients' preferences help to determine which antithrombotic therapy is optimal. Preference-based treatment should improve quality-adjusted survival and reduce medical expenditure in patients who have nonvalvular atrial fibrillation and not more than one additional risk factor for stroke.

Aged↗
PubMed1998

Use of medical informatics to implement and develop clinical practice guidelines.

Clinical practice guidelines have enormous potential to improve the quality of and accountability in health care. Making the most of this potential should become easier as guideline developers integrate guidelines within information systems and electronic medical records. A major barrier to such integration is the lack of computing infrastructure in many clinical settings. To successfully implement guidelines in information systems, developers must create more specific recommendations than those that have been required for traditional guidelines. Using reusable software components to create guidelines can make the development of protocols faster and less expensive. In addition, using decision models to produce guidelines enables developers to structure guideline problems systematically, to prioritize information acquisition, to develop site-specific guidelines, and to evaluate the cost-effectiveness of the explicit incorporation of patient preferences into guideline recommendations. Ongoing research provides a foundation for the use of guideline development tools that can help developers tailor guidelines appropriately to their practice settings. This article explores how medical informatics can help clinicians find, use, and create practice guidelines.

Decision Trees↗
PubMed1998

Design of a modular, extensible decision support system for arrhythmia therapy.

We developed a decision-support system for evaluation of treatment alternatives for supraventricular and ventricular arrhythmias. The system uses independent decision models that evaluate the costs and benefits of treatment for recurrent atrioventricular-node reentrant tachycardia (AVNRT), and of therapies to prevent sudden cardiac death (SCD) in patients at risk for life-threatening ventricular arrhythmias. Each of the decision models is accessible through a web-based interface that enables remote users to browse the model's underlying evidence and to perform analyses of effectiveness, cost effectiveness, and sensitivity to input variables. Because the web-based interface is independent of the models, we can extend the functionality of the system by adding decision models. This system illustrates that the use of a library of web-accessible decision models provides decision support economically to widely dispersed users.

Arrhythmias, Cardiac↗
PubMed1997

Monitored isoniazid prophylaxis for low-risk tuberculin reactors older than 35 years of age: a risk-benefit and cost-effectiveness analysis.

BACKGROUND: Isoniazid chemoprophylaxis effectively prevents the development of active infectious tuberculosis. Current guidelines recommend withholding this prophylaxis for low-risk tuberculin reactors older than 35 years of age because of the risk for fatal isoniazid-induced hepatitis. However, recent studies have shown that monitoring for hepatotoxicity can significantly reduce the risk for isoniazid-related death. OBJECTIVE: To evaluate the effectiveness and cost-effectiveness of monitored isoniazid prophylaxis for low-risk tuberculin reactors older than 35 years of age. DESIGN: A Markov model was used to compare the health and economic outcomes of prescribing or withholding a course of prophylaxis for low-risk reactors 35, 50, or 70 years of age. Subsequent analyses evaluated costs and benefits when the effect of transmission of Mycobacterium tuberculosis to contacts was included. MEASUREMENTS: Probability of survival at 1 year, number needed to treat, life expectancy, and cost per year of life gained for individual persons and total population. RESULTS: Isoniazid prophylaxis increased the probability of survival at 1 year and for all subsequent years. For 35-year old, 50-year-old, and 70-year-old tuberculin reactors, life expectancy increased by 4.9 days, 4.7 days, and 3.1 days, respectively, and costs per person decreased by $101, $69, and $11, respectively. When the effect of secondary transmission to contacts was included, the gains in life expectancy per person receiving prophylaxis were 10.0 days for 35-year-old reactors, 9.0 days for 50-year-old reactors, and 6.0 days for 70-year-old reactors. Costs per person for these cohorts decreased by $259, $203, and $100, respectively. The magnitude of the benefit of isoniazid prophylaxis is moderately sensitive to the effect of isoniazid on quality of life. The hypothetical provision of isoniazid prophylaxis for all low-risk reactors older than 35 years of age in the U.S. population could prevent 35,176 deaths and save $2.11 billion. CONCLUSIONS: Monitored isoniazid prophylaxis reduces mortality rates and health care costs for low-risk tuberculin reactors older than 35 years of age, although reductions for individual patients are small. For the U.S. population, however, the potential health benefits and economic savings resulting from wider use of monitored isoniazid prophylaxis are substantial. We should consider expanding current recommendations to include prophylaxis for tuberculin reactors of all ages with no contraindications.

Adult↗
PubMed1997

Cost-effectiveness of implantable cardioverter defibrillators relative to amiodarone for prevention of sudden cardiac death.

BACKGROUND: Implantable cardioverter defibrillators (ICDs) are remarkably effective in terminating ventricular arrhythmias, but they are expensive and the extent to which they extend life is unknown. The marginal cost-effectiveness of ICDs relative to amiodarone has not been clearly established. OBJECTIVE: To compare the cost-effectiveness of a third-generation implantable ICD with that of empirical amiodarone treatment for preventing sudden cardiac death in patients at high or intermediate risk. DESIGN: A Markov model was used to evaluate health and economic outcomes of patients who received an ICD, amiodarone, or a sequential regimen that reserved ICD for patients who had an arrhythmia during amiodarone treatment. MEASUREMENTS: Life-years gained, quality-adjusted life-years gained, costs, and marginal cost-effectiveness. RESULTS: For the base-case analysis, it was assumed that treatment with an ICD would reduce the total mortality rate by 20% to 40% at 1 year compared with amiodarone and that the ICD generator would be replaced every 4 years. In high-risk patients, if an ICD reduces total mortality by 20%, patients who receive an ICD live for 4.18 quality-adjusted life-years and have a lifetime expenditure of $88,400. Patients receiving amiodarone live for 3.68 quality-adjusted life-years and have a lifetime expenditure of $51,000. Marginal cost-effectiveness of an ICD relative to amiodarone is $74,400 per quality-adjusted life-year saved. If an ICD reduces mortality by 40%, the cost-effectiveness of ICD use is $37,300 per quality-adjusted life-year saved. Both choice of therapy (an ICD or amiodarone) and the cost-effectiveness ratio are sensitive to assumptions about quality of life. CONCLUSIONS: Use of an ICD will cost more than $50,000 per quality-adjusted life-year gained unless it reduces all-cause mortality by 30% or more relative to amiodarone. Current evidence does not definitively support or exclude a benefit of this magnitude, but ongoing randomized trials have sufficient statistical power to do so.

Amiodarone↗
PubMed1997

Physicians' assessments of the utility of health states associated with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infection.

An understanding of quality of life (QOL) with human immunodeficiency virus (HIV) is important because the merits of prevention and treatment alternatives may depend substantially on how these interventions affect QOL. Physicians' views about QOL are important, because they influence the therapeutic options that physicians consider or offer, the recommendations that physicians make, and because they are important for the analysis of certain policy questions. We assessed physicians' utilities of health states associated with HIV infection, and hepatitis B virus (HBV) infection; assessment of utilities for HBV was induced to provide a comparison with HIV utilities. We surveyed 200 housestaff and staff physicians in an academic medical centre by anonymous paper-based questionnaire and used the time-tradeoff method to assess physicians' utilities of the health states. On a scale in which 0 was equivalent to death, and 1 was equivalent to good health, the median utilities for asymptomatic HIV infection, symptomatic HIV infection, and AIDS were 0.833, 0.417, and 0.167, respectively (p < 0.01 or each two-way comparison). Median utilities for asymptomatic HBV infection, mildly symptomatic HBV infection, and severely symptomatic HBV infection were 0.917, 0.667, and 0.167, respectively (p < 0.01 for each two-way comparison). Although physicians varied substantially in the ratings of health states, they assessed the utility of life with HIV disease, including asymptomatic infection, as severely reduced. Studies of the effectiveness and cost-effectiveness of preventive and therapeutic interventions for HIV should evaluate the effect of the intervention on utility-based assessments of QOL. Studies that do not assess such effects may significantly underestimate or overestimate the value of these interventions, depending on the intervention's effect on QOL.

Acquired Immunodeficiency Syndrome↗
PubMed1996

The effect of stroke and stroke prophylaxis with aspirin or warfarin on quality of life.

BACKGROUND: Because most strokes cause neurological impairment rather than death, stroke prophylaxis may improve quality of life more than length of life. Thus, an understanding of how stroke and stroke prophylaxis affect quality of life is central to clinical decision making for many patients. METHODS: We elicited quality-of-life estimates, known as utilities, for 3 degrees of severity of anticipated stroke-mild, moderate, and major- and for stroke prophylaxis with either warfarin sodium or aspirin therapy. We used the time tradeoff and standard gamble methods to elicit these utilities from 83 patients who had atrial fibrillation. RESULTS: Seventy patients completed the interview successfully. Their utilities for stroke ranged from worse than death (< 0) to as good as current health (1.0). The median utilities for mild, moderate, and major stroke were 0.94, 0.07, and 0.0, respectively. Although the median utilities decreased with increasing severity of stroke (P < .001), there was high interpatient variability within each degree of stroke severity. For example, 7 subjects (10%) rated a major stroke above 0.5, while 58 subjects (83%) rated it as equal to or worse than death. In contrast to the stroke utilities, the median utilities for warfarin and aspirin therapy were high-0.997 and 1.0, respectively. However, the interpatient variability for warfarin therapy was also important: 11 patients (16%) with atrial fibrillation rated the utility of warfarin therapy so low that their quality-adjusted life expectancy would be greater with aspirin. CONCLUSION: Patients' utilities for stroke prophylaxis and anticipated stroke vary substantially. Many patients view the quality of life with major stroke as tantamount to or worse than death. These findings highlight the relevance of incorporating patient preferences when choosing stroke prophylaxis.

Aged↗
PubMed1996

Modelling cost-effectiveness of Helicobacter pylori screening to prevent gastric cancer: a mandate for clinical trials.

BACKGROUND: It is unknown whether eradication of Helicobacter pylori infection prevents development of gastric adenocarcinoma. To determine whether screening and treatment trials are warranted, we conducted a cost-effectiveness analysis to estimate the costs and benefits associated with screening for H pylori at age 50 and treating those individuals infected with antibiotics. METHODS: We compared two interventions: (1) screen for H pylori and treat those with a positive test, and (2) do not screen and do not treat. Estimates of risks and costs were obtained by review of published reports. Since the efficacy of H pylori therapy in cancer prevention is unknown, we did sensitivity analyses, varying this estimate widely. In our base-case analysis, we assumed that H pylori treatment prevented 30% of attributable gastric cancers. FINDINGS: In the base-case analysis, 11,646,000 persons in the US would be screened and 4,658,400 treated, at a cost of $996 million. Cost-effectiveness was $25,000 per year of life saved. Cost-effectiveness was sensitive to the efficacy of the cancer prevention strategy. At low efficacy rates (< 10%), the screening programme was more expensive (> $75,000 per year of life saved). In a high-risk group such as Japanese-Americans, however, screening and treatment required less than $50,000 per year of life saved, even at 5% treatment efficacy. INTERPRETATION: Screening and treatment for H pylori infection is potentially cost-effective in the prevention of gastric cancer, particularly in high-risk populations. Cancer prevention trials are strongly recommended.

Adenocarcinoma↗
PubMed1996

Polymerase chain reaction for the diagnosis of HIV infection in adults. A meta-analysis with recommendations for clinical practice and study design.

PURPOSE: To do a meta-analysis of studies that have evaluated the sensitivity and specificity of polymerase chain reaction (PCR) assay for the diagnosis of human immunodeficiency virus (HIV) infection in adults. Evaluating the performance of PCR is difficult because in certain clinical situations, the sensitivity or specificity of PCR may exceed those of the current reference standard tests (enzyme immunoassay followed by confirmatory Western blot analysis). Therefore, an additional goal was to develop recommendations for 1) the design of future evaluative studies of PCR and 2) the use of PCR in persons with suspected HIV infection. DATA SOURCES: Studies published between 1988 and 1994 that were identified in a search of 17 computer databases, including MEDLINE, and abstracts identified from conference proceedings. STUDY SELECTION: Studies were included if DNA amplification by PCR was done on peripheral blood mononuclear cells from adults. Ninety-six studies met the inclusion criteria. DATA EXTRACTION: Data were extracted independently by two reviewers. Study design was assessed independently by two investigators blinded to study results. RESULTS: Reported sensitivities for PCR range from 10% to 100%, and specificities range from 40% to 100%. A summary receiver-operating characteristic curve based on all 96 studies has a maximum joint sensitivity and specificity (upper left point on the curve, where sensitivity equals specificity) of 97.0% to 98.1%. If the threshold value that defines a positive PCR result is chosen so that sensitivity is higher than 98.1%, specificity will decrease to less than 98.1%. Conversely, if the threshold value that defines a positive PCR result is chosen so that specificity is greater than 98.1%, sensitivity will decrease to less than 98.1%. If sensitivity and specificity are chosen to be equal, the corresponding false-positive rate is 1.9% to 3.0%. At the maximum joint sensitivity and specificity, the positive predictive value of PCR ranges from 34% to 85% as the prevalence of HIV increases from 1.0% to 10%. We identified seven areas in which study design could be modified to 1) reduce susceptibility to bias in estimates of the sensitivity and specificity of PCR and 2) to increase the generalizability of the study results. These modifications will also help to overcome methodologic problems created by the lack of a reference standard test. CONCLUSIONS: The PCR assay is not sufficiently accurate to be used for the diagnosis of HIV infection without confirmation. Use of PCR for the diagnosis of HIV in adults should be limited to situations in which antibody tests are known to be insufficient. Future studies of PCR performance should be sufficiently large and should use adequate reference standard tests and standardized methods for the performance of PCR. Specimens should be evaluated by persons blinded to clinical status and to the results of other diagnostic tests for HIV infection.

Adult↗
PubMed1996

A meta-analytic evaluation of the polymerase chain reaction for the diagnosis of HIV infection in infants.

OBJECTIVE: To evaluate the sensitivity and specificity of the polymerase chain reaction (PCR) for the diagnosis of infection with human immunodeficiency virus (HIV) in infants. DATA SOURCES: We used studies published between 1988 and 1994 identified in a literature search of 17 databases, including MEDLINE. STUDY SELECTION: Studies were included if DNA amplification by PCR was performed on peripheral blood mononuclear cells from infants or children. DATA EXTRACTION: Two investigators independently extracted data. The study design was assessed independently by 2 investigators who were blinded to study results. DATA SYNTHESIS: Thirty-two studies met the inclusion criteria and were analyzed. The median reported sensitivity was 91.6% (range, 31%-100%), and the median specificity was 100% (range, 50%-100%). A summary receiver operating characteristic curve based on all 32 studies indicated that PCR has a maximum joint sensitivity and specificity between 93.2% and 94.9%. Subgroup analysis indicated that the joint sensitivity and specificity was significantly (P = .04) higher in older infants (98.2%) than in neonates (aged < or = 30 days; 93.3%). For infants at low risk of perinatal transmission (probability of transmission, 8.3%), the positive predictive value for PCR is 55.8% in neonates and 83.2% in older infants. A negative PCR result reduces the probability of HIV infection to less than 3%. No studies met all criteria for study design. CONCLUSIONS: Although PCR is one of the best available tests for diagnosis of HIV infection in neonates and infants, it is not definitive. Therefore, PCR should be interpreted with the aid of careful clinical follow-up examinations. The sensitivity and specificity of PCR in neonates is lower than in older infants, which results in a low positive predictive value; however, negative tests are informative. Delaying the use of PCR until after the neonatal period or repeating PCR on independent samples obtained 30 to 60 days later will reduce test errors.

Algorithms↗
PubMed1996

Cost-effectiveness of HIV screening in acute care settings.

BACKGROUND: Although screening inpatients for human immunodeficiency virus (HIV) in acute care hospital settings has been recommended, the cost-effectiveness of screening is not known. OBJECTIVE: To estimate the cost-effectiveness of a voluntary screening program in acute care hospitals and associated clinics. RESULTS: During the first year, an HIV screening program implemented in acute care hospital settings in which the seroprevalence of HIV infection is 1% or more would result in the identification of approximately 110,000 undetected cases of HIV infection. The program would result in expenditures of approximately $171 million for testing and counseling, and expenditures of approximately $2 billion for incremental medical care for the patients identified as having HIV infection during the first year of screening. When the seroprevalence of HIV is 1%, the cost-effectiveness of screening is $47,200 per year of life saved. When the effect of early identification of HIV infection on the patient's quality of life also is considered, screening is less cost-effective. Screening-induced reductions in risk behavior improve the cost-effectiveness of screening by preventing the transmission of HIV.

Acute Disease↗
PubMed1996

Presentation and explanation of medical decision models using the World Wide Web.

We demonstrated the use of the World Wide Web for the presentation and explanation of a medical decision model. We put on the web a treatment model developed as part of the Cardiac Arrhythmia and Risk of Death Patient Outcomes Research Team (CARD PORT). To demonstrate the advantages of our web-based presentation, we critiqued both the conventional paper-based and the web-based formats of this decision-model presentation with reference to an accepted published guide to understanding clinical decision models. A web-based presentation provides a useful supplement to paper-based publications by allowing authors to present their model in greater detail, to link model inputs to the primary evidence, and to disseminate the model to peer investigators for critique and collaborative modeling.

Arrhythmias, Cardiac↗