Economic analysis of influenza vaccination and antiviral treatment for healthy working adults

BACKGROUND

Physicians have several treatment options for influenza, including vaccination and various antiviral therapies. However, the optimal influenza prevention and treatment strategy is unknown.

OBJECTIVE

To compare the relative health values of contemporary treatment strategies for influenza in a healthy sample of working adults.

DESIGN

Cost-benefit analysis using a decision model.

DATA SOURCES

Previously published data.

TARGET POPULATION

Healthy employed adults 18 to 50 years of age.

TIME HORIZON

A complete influenza season.

PERSPECTIVE

Societal.

INTERVENTIONS

Eight treatment options (yes or no) based on the possible combinations of vaccination and antiviral therapy (rimantadine, oseltamivir, or zanamivir or no treatment) should infection develop.

OUTCOME MEASURES

Cost in U.S. dollars, including the value of symptom relief and medication side effects, which was assigned a monetary value through a conjoint analysis that used a "willingness-to-pay" approach.

RESULTS

In the base-case analysis, all strategies for influenza vaccination had a higher net benefit than the nonvaccination strategies. Vaccination and use of rimantadine, the most cost-beneficial strategy, was $30.97 more cost-beneficial than nonvaccination and no use of antiviral medication. The health benefits of most antiviral treatments equaled or exceeded their costs for most scenarios. The choice of the most cost-beneficial antiviral strategy was sensitive to the prevalence of influenza B and to the comparative workdays gained by each antiviral therapy.

CONCLUSIONS

Vaccination is cost-beneficial in most influenza seasons in healthy working adults. Although the benefits of antiviral therapy for persons with influenza infection appear to justify its cost, head-to-head trials of the various antiviral therapies are needed to determine the optimal treatment strategy.

Management of uterine leiomyomata: what do we really know?

OBJECTIVE

To systematically review the literature on the surgical and nonsurgical management of uterine leiomyomata.

DATA SOURCES

Published literature in English on the management of uterine leiomyomata published from 1975 through 2000 was identified in MEDLINE, CINAHL, CancerLit, EMBASE, HealthSTAR, and the Cochrane Database of Systematic Reviews. Search terms included "leiomyomata," "fibroids," "hysterectomy," and "myomectomy."

STUDY SELECTION

Study designs considered included controlled trials, prospective trials with historical controls, prospective or retrospective cohort studies, and series with at least 20 cases. Original research studies or relevant reviews were included if the study population included women with uterine leiomyomata, and data were provided relevant to one or more of nine prespecified research questions.

TABULATION, INTEGRATION, AND RESULTS

Inconsistency in reporting of severity of symptoms, uterine anatomy, and response to therapy prevented meaningful comparison of studies in most cases, and prevented performance of meta-analysis in all cases. This was true of both surgical and nonsurgical treatments.

CONCLUSION

The available evidence on the management of uterine leiomyomata is of poor quality. Patients, clinicians, and policymakers do not have the data needed to make informed decisions about appropriate treatment. Given the prevalence of this condition and its substantial impact on women's lives, obtaining these data should be a high research priority.

Disease management in healthcare organizations: results of in-depth interviews with disease management decision makers

BACKGROUND

Despite the widening use of disease management (DM) programs throughout the country, little is understood about the "state of DM" in healthcare systems and managed care organizations.

OBJECTIVE

To better characterize the range of users of DM in healthcare and to identify critical issues, both present and future, for DM.

STUDY DESIGN

Qualitative survey.

PARTICIPANTS AND METHODS

Forty-seven healthcare systems (n = 22) and managed care organizations (n = 25) were randomly selected. Decision makers were identified and interviewed between January 1, 2000, and March 31, 2000. We limited quantitative analysis to tabulations of suitable responses, without statistical testing. Responses were organized around 3 themes: models for DM, implementation strategies, and measurements of success.

RESULTS

Of 47 decision makers surveyed, 42 (89%) reported that their organizations currently have (75%) or are working to develop (14%) DM programs. Although the goals of DM programs were similar, organizations took a variety of approaches to achieving these ends. There were typically 3 steps in implementing a DM program: analysis of patient data, external analysis, and organizational analysis. Decision makers believed that DM programs had only achieved partial success in reaching the 2 main goals of improved quality of care and cost savings.

CONCLUSIONS

Given the variety of DM programs, there is a need to develop a classification scheme to allow for better comparison between programs. Further quantitative studies of decision makers' opinions would be helpful in developing programs and in designing necessary studies of patient management strategies.

Improving the quality of anticoagulation of patients with atrial fibrillation in managed care organizations: results of the managing anticoagulation services trial

Randomized trials have indicated that well-managed anticoagulation with warfarin could prevent more than half of the strokes related to atrial fibrillation. However, many patients with atrial fibrillation who are eligible for this therapy either do not receive it or are not maintained within an optimal prothrombin time-international normalized ratio (INR) range. We sought to determine whether an anticoagulation service within a managed care organization would be a feasible alternative for providing anticoagulation care. We performed a multi-site randomized trial in six large managed care organizations in the United States. Subjects were aged 65 years or older and had nonvalvular atrial fibrillation. At each site, physician practices were divided into two geographically defined practice clusters; each site was randomly assigned to have one intervention and one control cluster. The intervention cluster received an anticoagulation service that satisfied specifications for high-quality anticoagulation care and was coordinated through the managed care organization. Control clusters continued with their usual provider-based care. We measured the proportion of time that warfarin-treated patients in each of the clusters (intervention and control) were in the target range for the INR at baseline, and again during a follow-up period. Five of the six selected sites succeeded at developing an anticoagulation service. Patients in the intervention and control clusters had similar demographic characteristics, contraindications to warfarin, and risk factors for stroke. Among patients (n = 144 in the intervention clusters; n = 118 in the control clusters) for whom data were available during the baseline and follow-up periods, the changes in percentages of time in the target range were similar for those in the intervention clusters (baseline: 47.7%; follow-up: 55.6%) and in the control clusters (baseline: 49.1%; follow-up: 52.3%; intervention effect: 5%; 95% confidence interval: -5% to 14%; P = 0.32). Although it was feasible in a managed care organization to implement anticoagulation services that were tailored to local circumstances, provision of this service did not improve anticoagulation care compared with usual care. The effect of the anticoagulation service was limited by the utilization of the service, the degree to which the referring physician supports strict adherence to recommended target ranges for the INR, and the ability of the anticoagulation service to identify and to respond to out-of-range values promptly.

Cost-effectiveness of ancrod treatment of acute ischaemic stroke: results from the Stroke Treatment with Ancrod Trial (STAT)

RATIONALE, AIMS AND OBJECTIVES

This paper describes a recent randomized controlled trial in which 42% of patients receiving ancrod attained a favourable outcome in comparison with 34% of controls. Although the above effect size corresponds to a number needed to treat (to achieve a favourable outcome) of approximately 13, intuition does not necessarily suggest what would be the overall impact of a treatment with this level of efficacy.

METHODS

The objective was to evaluate the cost-effectiveness of ancrod. Cost-effectiveness analysis of data from the Stroke Treatment with Ancrod Trial (STAT) trial was carried out. The participants were 495 patients with data on functional status at the conclusion of follow-up. Short-term results were based upon utilization and quality of life observed during the trial; these were merged with expected long-term results obtained through simulation using the Stroke Policy Model. The main outcome measure was incremental cost-effectiveness ratio.

RESULTS

Ancrod treatment resulted in both better quality-adjusted life expectancy and lower medical costs than placebo as supported by sensitivity analysis. The cost differential was primarily attributable to the long-term implications of ancrod's role in reducing disability.

CONCLUSIONS

If ancrod is even modestly effective, it will probably be cost-effective (and, indeed, cost-saving) as well. The net population-level impact of even modestly effective stroke treatments can be substantial.

Use of data from nonrandomized trial designs in evidence reports: an application to treatment of pulmonary disease following spinal cord injury

Evidence reports summarize the evidence pertaining to various health-related topics. Including evidence from nonrandomized studies into such reports involves a trade-off between availability and bias. We describe a general framework by which information from nonrandomized studies might be integrated reasonably into evidence reports and illustrate its application to a recent evidence report on preventing pulmonary complications among patients with spinal cord injury. The proposed framework, which is based upon the premise that producing a fair summary of the evidence requires only a level of evidence judged by clinical experts to be sufficient to the task at hand, may help focus scarce resources, strengthen the quality and documentation of decisions including evidence from nonrandomized studies, and suggest high-priority areas for future research.

Improving the reliability of stroke subgroup classification using the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria

BACKGROUND AND PURPOSE

We sought to improve the reliability of the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification of stroke subtype for retrospective use in clinical, health services, and quality of care outcome studies. The TOAST investigators devised a series of 11 definitions to classify patients with ischemic stroke into 5 major etiologic/pathophysiological groupings. Interrater agreement was reported to be substantial in a series of patients who were independently assessed by pairs of physicians. However, the investigators cautioned that disagreements in subtype assignment remain despite the use of these explicit criteria and that trials should include measures to ensure the most uniform diagnosis possible.

METHODS

In preparation for a study of outcomes and management practices for patients with ischemic stroke within Department of Veterans Affairs hospitals, 2 neurologists and 2 internists first retrospectively classified a series of 14 randomly selected stroke patients on the basis of the TOAST definitions to provide a baseline assessment of interrater agreement. A 2-phase process was then used to improve the reliability of subtype assignment. In the first phase, a computerized algorithm was developed to assign the TOAST diagnostic category. The reliability of the computerized algorithm was tested with a series of synthetic cases designed to provide data fitting each of the 11 definitions. In the second phase, critical disagreements in the data abstraction process were identified and remaining variability was reduced by the development of standardized procedures for retrieving relevant information from the medical record.

RESULTS

The 4 physicians agreed in subtype diagnosis for only 2 of the 14 baseline cases (14%) using all 11 TOAST definitions and for 4 of the 14 cases (29%) when the classifications were collapsed into the 5 major etiologic/pathophysiological groupings (kappa=0.42; 95% CI, 0.32 to 0.53). There was 100% agreement between classifications generated by the computerized algorithm and the intended diagnostic groups for the 11 synthetic cases. The algorithm was then applied to the original 14 cases, and the diagnostic categorization was compared with each of the 4 physicians' baseline assignments. For the 5 collapsed subtypes, the algorithm-based and physician-assigned diagnoses disagreed for 29% to 50% of the cases, reflecting variation in the abstracted data and/or its interpretation. The use of an operations manual designed to guide data abstraction improved the reliability subtype assignment (kappa=0.54; 95% CI, 0.26 to 0.82). Critical disagreements in the abstracted data were identified, and the manual was revised accordingly. Reliability with the use of the 5 collapsed groupings then improved for both interrater (kappa=0.68; 95% CI, 0.44 to 0.91) and intrarater (kappa=0.74; 95% CI, 0.61 to 0.87) agreement. Examining each remaining disagreement revealed that half were due to ambiguities in the medical record and half were related to otherwise unexplained errors in data abstraction.

CONCLUSIONS

Ischemic stroke subtype based on published TOAST classification criteria can be reliably assigned with the use of a computerized algorithm with data obtained through standardized medical record abstraction procedures. Some variability in stroke subtype classification will remain because of inconsistencies in the medical record and errors in data abstraction. This residual variability can be addressed by having 2 raters classify each case and then identifying and resolving the reason(s) for the disagreement.

Have randomized controlled trials of neuroprotective drugs been underpowered? An illustration of three statistical principles

BACKGROUND AND PURPOSE

The results of phase III trials of neuroprotective drugs for acute ischemic stroke have been disappointing. We examine the question of whether these trials may have been underpowered.

METHODS

Computer simulations were based on the binomial distribution.

RESULTS

We illustrate that even small overestimates of the efficacy of an intervention can lead to a serious reduction in statistical power, that the use of data from phase II studies tends to lead to such overestimation, and that a minimum clinically important difference derived with cost-effectiveness modeling techniques is considerably smaller than might be suggested by intuition.

CONCLUSIONS

We recommend placing more emphasis on minimum clinically important differences when planning stroke trials, with these differences being derived from an assessment of the public health impact obtained in conjunction with the use of epidemiological and cost-effectiveness models. Even small benefits, when averaged over a sufficiently large number of cases, will, in total, accrue to a large positive impact on the public health.

Improved Reliability of Stroke Classification Using the TOAST Criteria

P35

PURPOSE. Improve the reliability of stroke subtype classification. BACKGROUND. We previously found that the reliability of stroke subtype assignment using the TOAST criteria was only fair. In a two phase process to improve inter-rater agreement, we first developed a computerized algorithm for diagnositic categorization (Neurology 1999; 52: A243). In this second phase, residual variability related to differences in data abstraction was systematically assessed and reduced. METHODS. To assess baseline levels of inter-rater agreement, 4 physicians first retrospectively assigned TOAST subtype diagnoses for a randomly selected series of 14 patients. These diagnoses were then compared with those assigned by the computerized algorithm. Critical disagreements in data abstraction were identified and remaining variability reduced with the development of standardized abstraction procedures. Inter- and intra-rater reliability were reassessed in separate randomly selected groups of cases. RESULTS. There was fair to moderate agreement between the algorithm-based and physician-assigned diagnoses for the baseline cases (kappa, k = 0.41, 95% CI: 0.28, 0.54), reflecting variation in the abstracted data and/or its interpretation. The development of standardized abstraction procedures improved reliability to a moderate level (k=0.54, 95% CI: 0.26, 0.82). Critical disagreements (primarily due to differences in the interpretations of CT and MRI scans, cardiovascular evaluations, and ultrasound results) were identified and abstraction procedures revised accordingly. Reliability then improved to substantial levels of both inter-rater (k=0.68, 95% CI: 0.44, 0.91) and intra-rater (k=0.74, 95% CI 0.61,0.87) agreement. Half of remaining disagreements were due to ambiguities in the medical record and half related to errors in data abstraction. CONCLUSION. TOAST subtype classifications can be reliably assigned using a computerized algorithm with data obtained through standardized medical record abstraction. This residual variability can be addressed by having two raters classify each case and then identifying and resolving the reason(s) disagreements.

Have Randomized Controlled Trials of Neuroprotective Drugs Been Underpowered?: An Illustration of Three Statistical Principles

P185

Background and Purpose — The results of phase III trials of neuroprotective drugs for acute ischemic stroke have been disappointing. We examine the question of whether these trials may have been underpowered. Methods — Computer simulations were based upon the binomial distribution. Results — We illustrated that even small overestimates of the efficacy of an intervention can lead to a serious reduction in statistical power, that use of data from phase II studies tends to lead to such overestimation, and that a minimum clinically important difference derived using cost-effectiveness modeling techniques is considerably smaller than might be suggested by intuition. Conclusions — We recommend placing more emphasis on minimum clinically important differences when planning stroke trials, with these differences being derived from an assessment of public health impact obtained in conjunction with the use of epidemiologic and cost-effectiveness models. Even small benefits, when averaged over a sufficiently large number of cases, will, in total, accrue to a large positive impact on the public health.

Anticoagulation for Atrial Fibrillation: Physicians’ Readiness to Change Practices

94

PURPOSE. Determine physicians’ readiness to change anticoagulation practices for patients with non-valvular atrial fibrillation (NVAF). BACKGROUND. Only half of eligible NVAF patients receive warfarin. Interventions to alter physicians’ anticoagulation practices must consider their motivation to change. METHODS. As part of a US national survey (1993–94), physicians were asked their current practices for patients over age 65 with NVAF, and whether they were comfortable, considering change, or expecting to change those practices. RESULTS. Overall, 67% of eligible physicians fully responded to the survey (n=1006). Seventy-three percent (72% of non-internist primary care physicians [PCPs], 76% of internists, 69% of neurologists and 37% of surgeons) responded that they often or always anticoagulate patients over age 65 with NVAF. The majority (73%) indicated they were comfortable with their practices, with the rates differing by specialty (68% PCPs, 76% internists, 82% neurologists, 87% surgeons; p<0.001). Regardless of specialty, 78% of physicians who seldom or never anticoagulate this type of patient were comfortable with this practice. An identical proportion of physicians indicating they always or often use anticoagulants for patients with NVAF were comfortable with their practices. CONCLUSION. Although differing by specialty, these data show that the majority of physicians are not expecting or planning to change their anticoagulation practices for patients over age 65 with NVAF. Although the majority believe they anticoagulate such patients and are comfortable with their practices, their actual treatment patterns may differ as several studies show that high proportions of eligible AF patients do not receive warfarin. Utilization review coupled with the identification of specific practice barriers and tailored educational programs may address this discrepancy. A high proportion of physicians who responded that they seldom or never anticoagulate these patients were also comfortable with their practices. Providing current treatment guidelines reinforced by other educational strategies might motivate them to consider a change in practice.

Setting the target for a better cervical screening test: characteristics of a cost-effective test for cervical neoplasia screening

OBJECTIVE

To determine the potential effects on costs and outcomes of changes in sensitivity and specificity with new screening methods for cervical cancer.

METHODS

Using a Markov model of the natural history of cervical cancer, we estimated the effects of sensitivity, specificity, and screening frequency on cost-effectiveness. Our estimates of conventional Papanicolaou test sensitivity of 51% and specificity of 97% were obtained from a meta-analysis. We estimated the effect of reducing false-negative rates from 40-90% and increasing false-positive rates by up to 20%, independently and jointly. We varied the marginal cost of improving sensitivity from $0 to $15.

RESULTS

When specificity was held constant, increasing sensitivity of the Papanicolaou test increased life expectancy and costs. When sensitivity was held constant, decreasing specificity of the Papanicolaou test increased costs, an effect that was more dramatic at more frequent intervals. Decreased specificity had a substantial effect on cost-effectiveness estimates of improved Papanicolaou test sensitivity. Most of those effects are related to the cost of evaluation and treatment of low-grade lesions.

CONCLUSION

Policies or technologies that increased sensitivity of cervical cytologic screening increased overall costs, even if the cost of the technology was identical to that of conventional Papanicolaou smears. These effects appear to be caused by relatively high prevalence of low-grade lesions and are magnified at frequent screening intervals. Efficient cervical cancer screening requires methods with greater ability to detect lesions that are most likely to become cancerous.

Economics of low-molecular weight heparins

Low-molecular weight heparins (LMWHs) have become attractive alternatives to standard unfractionated heparin (UFH) for the treatment and prophylaxis of deep vein thrombosis (DVT), and for the management of acute coronary syndrome (ACS). The economic impact of the use of LMWHs has been studied in randomized controlled studies, in demonstration projects in managed care institutions, and in decision models. These studies provide valuable insight into the ways LMWHs can be economically attractive despite higher per unit costs compared with UFH. For the treatment of DVT, the cost benefit of using LMWHs results primarily from the cost shifting from inpatient to outpatient care, and might be limited by the eligibility of patients for outpatient management. In contrast, the attractiveness of LMWHs for ACS and DVT prophylaxis hinges on the increased effectiveness of LMWHs compared with standard UFH.

Depression and other determinants of values placed on current health state by stroke patients: evidence from the VA Acute Stroke (VASt) study

BACKGROUND AND PURPOSE

This prospective study examined the determinants of the utility (value) placed on health status among a sample of patients with acute ischemic and intracerebral hemorrhagic stroke.

METHODS

Data were from the VA Acute Stroke (VASt) study, a nationwide prospective cohort of 1073 acute stroke patients admitted at any of 9 Department of Veterans Affairs Medical Center sites between April 1, 1995, and March 31, 1997. The primary outcome was the patient's health status utility as measured by the time-tradeoff method. Data were obtained by telephone interviews at 1, 6, and 12 months and by medical record review. General linear mixed modeling was used to assess the effects of social, psychological, and physical factors on patients' valuations of their current health state. The analysis was confined to the 327 patients who were able to provide self-reports at >/=2 time points.

RESULTS

Patients' valuations of their health state status over the initial 12 months after stroke were very stable over time, with only a slight improvement at 6 months, followed by a slight decline at 12 months. In adjusted analyses, living alone, being institutionalized, decreased physical function, and depression were independently associated with lower levels of patient health status utility over time.

CONCLUSIONS

Stroke patient health status utilities are relatively stable during the initial year after stroke. In addition to physical function, psychological health and social environment are important determinants of patient health status utility. These factors need to be considered when conducting stroke decision analyses if more accurate conclusions are to be drawn regarding preferred patterns of care.

New transient ischemic attack and stroke: outpatient management by primary care physicians

BACKGROUND

Patients with transient ischemic attack (TIA) or stroke frequently first contact their primary care physician rather than seeking care at a hospital emergency department. The purpose of the present study was to identify a group of patients seen by primary care physicians in an office setting for a first-ever TIA or stroke and characterize their evaluation and management.

METHODS

Practice audit based on retrospective, structured medical record abstraction from 27 primary care medical practices in 2 geographically separate communities in the eastern United States.

RESULTS

Ninety-five patients with a first-ever TIA and 81 with stroke were identified. Seventy-nine percent of those with TIA vs 88% with stroke were evaluated on the day their symptoms occurred (P =.12). Only 6% were admitted to a hospital for evaluation and treatment on the day of the index visit (2% TIA; 10% stroke; P =.03); only an additional 3% were admitted during the subsequent 30 days. Specialists were consulted for 45% of patients. A brain imaging study (computed tomography or magnetic resonance imaging) was ordered on the day of the index visit in 30% (23% TIA, 37% stroke; P =.04), regardless of whether the patient was referred to a specialist. Carotid ultrasound studies were obtained in 28% (40% TIA, 14% stroke; P<.001), electrocardiograms in 19% (18% TIA, 21% stroke; P =.60), and echocardiograms in 16% (19% TIA, 14% stroke; P =.34). Fewer than half of patients with a prior history of atrial fibrillation (n = 24) underwent anticoagulation when evaluated at the index visit. Thirty-two percent of patients (31% TIA, 33% stroke; P =.70) were not hospitalized and had no evaluations performed during the first month after presenting to a primary care physician with a first TIA or stroke. Of these patients, 59% had a change in antiplatelet therapy on the day of the index visit.

CONCLUSIONS

Further primary care physician education regarding the importance of promptly and fully evaluating patients with TIA or stroke may be warranted, and barriers to implementation of established secondary stroke prevention strategies need to be carefully explored. Arch Intern Med. 2000;160:2941-2946

Mathematical model for the natural history of human papillomavirus infection and cervical carcinogenesis

The authors constructed a Markov model as part of a systematic review of cervical cytology conducted at the Duke University Evidence-based Practice Center (Durham, North Carolina) between October 1997 and September 1998. The model incorporated states for human papillomavirus infection (HPV), low- and high-grade squamous intraepithelial lesions, and cervical cancer stages I-IV to simulate the natural history of HPV infection in a cohort of women from ages 15 to 85 years. The age-specific incidence rate of HPV, and regression and progression rates of HPV and squamous intraepithelial lesions, were obtained from the literature. The effects of varying natural history parameters on cervical cancer incidence were evaluated by using sensitivity analysis. The base-case model resulted in a lifetime cervical cancer risk of 3.67% and a lifetime cervical cancer mortality risk of 1.26%, with a peak incidence of 81/100,000 at age 50 years. Age-specific distributions of precursors were similar to reported data. Lifetime risk of cancer was most sensitive to the incidence of HPV and the probability of rapid HPV progression to high-grade lesions (two- to threefold variations in risk). The model approximates the age-specific incidence of cervical cancer and provides a tool for evaluating the natural history of HPV infection and cervical cancer carcinogenesis as well as the effectiveness and cost-effectiveness of primary and secondary prevention strategies.

Community impact of anticoagulation services: rationale and design of the Managing Anticoagulation Services Trial (MAST)

We describe the design of the Managing Anti-coagulation Services Trial (MAST), a practice-improvement trial testing whether anticoagulation services are a preferred method of managing anticoagulation for stroke prevention among patients with atrial fibrillation. Most randomized trials within the health care environment are designed as efficacy studies to determine what works under ideal conditions or ideal clinical practice. In contrast, effectiveness trials seek to generalize the results of efficacy studies by determining what works under more typical practice conditions. Practice-improvement trials are effectiveness trials that examine the management of a clinical problem in the context in which care is usually given. Noteworthy features of the MAST include defining the intervention in functional terms and collaboration with managed care organizations.

Accuracy of the Papanicolaou test in screening for and follow-up of cervical cytologic abnormalities: a systematic review

PURPOSE

To evaluate the accuracy of conventional and new methods of Papanicolaou (Pap) testing when used to detect cervical cancer and its precursors.

DATA SOURCES

Systematic search of English-language literature through October 1999 using MEDLINE, EMBASE, other computerized databases, and hand searching.

STUDY SELECTION

All studies that compared Pap testing (conventional methods, computer screening or rescreening, or monolayer cytology) with a concurrent reference standard (histologic examination, colposcopy, or cytology).

DATA EXTRACTION

Two reviewers independently reviewed selection criteria and completed 2 x 2 tables for each study.

DATA SYNTHESIS

94 studies of the conventional Pap test and three studies of monolayer cytology met inclusion criteria. No studies of computerized screening were included. Data were organized by cytologic and histologic thresholds used to define disease. For conventional Pap tests, estimates of sensitivity and specificity varied greatly in individual studies. Methodologic quality and frequency of histologic abnormalities also varied greatly between studies. In the 12 studies with the least biased estimates, sensitivity ranged from 30% to 87% and specificity ranged from 86% to 100%.

CONCLUSIONS

Insufficient high-quality data exist to estimate test operating characteristics of new cytologic methods for cervical screening. Future studies of these technologies should apply adequate reference standards. Most studies of the conventional Pap test are severely biased: The best estimates suggest that it is only moderately accurate and does not achieve concurrently high sensitivity and specificity. Cost-effectiveness models of cervical cancer screening should use more conservative estimates of Pap test sensitivity.

Quality of anticoagulation management among patients with atrial fibrillation: results of a review of medical records from 2 communities

BACKGROUND

Most treatment of patients at risk for stroke is provided in the ambulatory setting. Although many studies have addressed the proportion of eligible patients with atrial fibrillation (AF) receiving warfarin sodium, few have addressed the quality of their anticoagulation management.

OBJECTIVE

As a comprehensive assessment of quality, we analyzed the proportion of eligible patients receiving warfarin, the proportion of time their international normalized ratios (INRs) were within the target range, and, when an out-of-target range INR value occurred, the time until the next INR measurement was made.

METHODS

Retrospective review of the medical records of 660 patients with AF managed by general internists and family practitioners in Rochester, NY, and the Research Triangle area of North Carolina.

RESULTS

Only 34.7% of eligible patients with AF received warfarin. The INR values were out of the target range approximately half the time, and the response to these values was not always timely. For all the measures considered, both Rochester practices with access to an anticoagulation service had higher (albeit not ideal) quality of warfarin management than the remaining practices.

CONCLUSIONS

We found significant deficiencies in the practice of warfarin management and suggestive evidence that anticoagulation services can partially ameliorate these deficiencies. More research is needed to describe the quality of anticoagulation management in typical practice and how this management can be improved.

Relationship between test frequency and outcomes of anticoagulation: a literature review and commentary with implications for the design of randomized trials of patient self-management

BACKGROUND

Patient self-management (PSM) of anticoagulation, which is primarily based upon the premise that more frequent testing will lead to tighter anticoagulation control and thus to improved clinical outcomes, is a promising model of care. The goals of this paper are (1) to describe the strength of evidence correlating more frequent testing with improved outcomes; and (2) to discuss implications of these findings for the design of randomized controlled trials (RCTs) assessing the effectiveness and cost-effectiveness of PSM.

METHODS

We performed two literature reviews: one examining the strength of the relationship between time in target range (TTR) and the clinical outcomes of major bleeding and thromboembolism; and the second examining the strength of the relationship between frequency of testing and TTR.

RESULTS

We found that (1) the relationship between TTR and clinical outcomes is strong, thus supporting use of TTR as a primary outcome variable; and (2) more frequent testing seems to increase TTR, although the studies supporting this latter conclusion were relatively few and not definitive. Statistical analysis suggested that a study which uses clinical event rates as its primary outcome would need to be much larger than a comparable study which is based upon TTR.

CONCLUSIONS

When designing randomized trials of PSM, the design should (1) use as its control group high quality anticoagulation management rather than usual care; (2) include the maximum possible amount of self-management in the intervention group; (3) include different testing intervals in the intervention group; (4) use TTR as the primary outcome variable and event rates as a secondary outcome; and (5) base the sample size calculations upon a 5-10% absolute improvement in TTR. Additional RCTs are needed in order to determine how the promise of PSM can best be fulfilled.

Racial variation in treatment for transient ischemic attacks: impact of participation by neurologists

OBJECTIVE

This study evaluates the role of neurologists in explaining African American-white differences in the use of diagnostic and therapeutic services for cerebrovascular disease.

DATA SOURCES/STUDY SETTING

Medicare inpatient hospital records were used to identify a random 20 percent sample of patients age 65 and over hospitalized with a principal diagnosis of TIA between January 1, 1991 and November 30, 1991 (n = 17,437).

STUDY DESIGN

Medicare administrative data were used to identify five outcome measures: noninvasive cerebrovascular tests, cerebral angiography, carotid endarterectomy, anticoagulant therapy (as proxied by outpatient prothrombin time tests), and the specialty of the attending physician (neurologist versus other specialist).

DATA COLLECTION/EXTRACTION METHODS

All Medicare claims were extracted for a 30-day period beginning with the date of admission.

PRINCIPAL FINDINGS

Even after adjusting for patient demographics, comorbidity, ability to pay, and provider characteristics, African American patients were significantly less likely to receive noninvasive cerebrovascular testing, cerebral angiography, or carotid endarterectomy, compared with white patients, and to have a neurologist as their attending physician. At the same time, patients treated by neurologists were more likely to undergo diagnostic testing and less likely to undergo carotid endarterectomy.

CONCLUSIONS

The findings suggest that African American patients with TIA may have less access to services for cerebrovascular disease and that at least some of this may be attributed to less access to neurologists. More research is needed on how patients at risk for stroke are referred to specialists.

Racial variation in initial stroke severity

BACKGROUND AND PURPOSE

Blacks experience greater morbidity and mortality from stroke than do whites. The degree to which this is due to the severity of the initial stroke is not known. The objective of this study is to determine whether there is a racial difference in initial stroke severity.

METHODS

A secondary analysis of a prospective cohort of 984 veterans (29.7% black) admitted to any of 9 geographically diverse Veterans Administration Hospitals for acute stroke between April 1995 and March 1997 was performed. Initial stroke severity was ascertained by using the modified Canadian Neurological Scale (CNS) applied retrospectively to medical record data. Stroke severity, unadjusted and adjusted for covariates, was compared between black and white patients.

RESULTS

Blacks had greater initial stroke severity than did whites (mean CNS score 7.96 versus 8.32, respectively; P=0.039), with a 0.5-point difference on the scale corresponding to a single-level decrement in either speech or strength of half of an extremity. This difference persisted with adjustment for other important predictors of stroke severity (P=0. 035). However, there was no significant racial difference in severity when CNS scores were collapsed into a priori clinically relevant categories.

CONCLUSIONS

Compared with whites, blacks show greater severity of stroke at hospital admission. It remains uncertain whether the relatively small but significant difference at presentation fully explains the striking racial differences in morbidity and mortality from stroke.

Incidence and occurrence of total (first-ever and recurrent) stroke

BACKGROUND AND PURPOSE

It has recently been hypothesized that the figure of approximately half a million strokes substantially underestimates the actual annual stroke burden for the United States. The majority of previously reported studies on the epidemiology of stroke used relatively small and homogeneous population-based stroke registries. This study was designed to estimate the occurrence, incidence, and characteristics of total (first-ever and recurrent) stroke by using a large administrative claims database representative of all 1995 US inpatient discharges.

METHODS

We used the Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project, release 4, which contains approximately 20% of all 1995 US inpatient discharges. Because the accuracy of International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) coding is suboptimal, we performed a literature review of ICD-9-CM 430 to 438 validation studies. The pooled results from the literature review were used to make appropriate adjustments in the analysis to correct for some of the inaccuracies of the diagnostic codes.

RESULTS

There were 682 000 occurrences of stroke with hospitalization (95% CI 660 000 to 704 000) and an estimated 68 000 occurrences of stroke without hospitalization. The overall incidence rate for occurrence of total stroke (first-ever and recurrent) was 259 per 100 000 population (age- and sex-adjusted to 1995 US population). Incidence rates increased exponentially with age and were consistently higher for males than for females.

CONCLUSIONS

We conservatively estimate that there were 750 000 first-ever or recurrent strokes in the United States during 1995. This new figure emphasizes the importance of preventive measures for a disease that has identifiable and modifiable risk factors and for the development of new and improved treatment strategies and infrastructures that can reduce the consequences of stroke.

Incorporation of patient preferences in the treatment of upper urinary tract calculi: a decision analytical view

PURPOSE

Patient preferences, or utilities, may be crucial to select an appropriate treatment plan for stone disease. We used decision modeling to understand better patient choices and decision making in the overall management of recurrent nephrolithiasis.

MATERIALS AND METHODS

We interviewed 180 consecutive patients with active stone disease. Demographic data and historical experiences with calculi were recorded. Patients were presented with 6 hypothetical clinical scenarios and various treatment options. The standard gamble method was used to obtain utility values for each option.

RESULTS

Nephrectomy had the lowest mean utility value of 0.883. Percutaneous nephrolithotomy for severe, moderate and mild pain had utilities of 0.924, 0.932 and 0.947, respectively. Shock wave lithotripsy for the management of mild pain was the most attractive option (mean utility 0.968). The utility for long-term medical therapy was 0.949, which was between that of percutaneous nephrolithotomy and shock wave lithotripsy for mild pain. Patients with a surgical history of stone removal assigned lower utilities to invasive procedures (nephrectomy, percutaneous nephrolithotomy, p <0.05). As the incidence of spontaneous stone passage increased, a higher utility was given to long-term medical therapy (p <0.05). Patients on medical therapy less than 1 year did not appreciate a significant benefit of medical prophylaxis. However, longer compliance with medical management led patients to perceive increasing benefits of continuing such medical treatment (p <0.05). Patients who had undergone stone removal via endoscopic or open surgery also had a higher preference for medical therapy (p <0.05).

CONCLUSIONS

Patients who had undergone stone removal wanted to avoid future invasive procedures. They ranked long-term medical therapy below shock wave lithotripsy but above invasive procedures, such as percutaneous nephrolithotomy. Most importantly, patients appreciated the benefits of medical therapy the longer that they complied with specific recommendations. These results support the concept that patients perceive long-term medical therapy to prevent recurrent nephrolithiasis as a desirable treatment option.

The role of evidence reports in evidence-based medicine: a mechanism for linking scientific evidence and practice improvement

STUDY QUESTIONS

In this article two related questions are considered: (1) Why isn't evidence-based medicine (EBM) more consistently implemented? and (2) Using the EBM paradigm, by what mechanism can we link evidence reports to concrete practice improvement activities?

STUDY DESIGN

To motivate a systematic analysis, answers to these questions are framed within the context of a general conceptual model for practice improvement, using as an example the application of this general model to the question of improving anticoagulation.

CONCLUSIONS

The potential role of evidence reports is quite broad and to be most effective, they should (1) be considered as part of a comprehensive strategy for practice improvement and (2) be designed with their customers in mind. A system-based method for using the information from evidence reports involves ultimately suggesting specific practice improvement strategies in which the strategies are defined in terms of (1) a set of functional specifications and (2) a toolbox of implementation options. Such an approach brings to bear the specialized expertise and generalized fund of scientific knowledge used to produce the evidence report, but does so in a way that facilitates local tailoring. That is, while information synthesis should be global, implementation must be local.

Using outcomes data to identify best medical practice: the role of policy models

Increasingly, physicians are attempting to incorporate best evidence into their clinical decision making. However, best evidence takes a variety of forms, including clinical trials, cohort studies, administrative data, and patient preference data. Incorporating multiple data sources in a way that informs complex clinical decisions is a substantial analytical challenge. One approach to this challenge is to develop a simulation/decision model that explicitly represents the natural history of disease and the impact of treatments on that natural history. The model should be requisite--that is, sufficient in form to address the decision problem--but not overly complex. Such a model can be of value because it (1) allows a variety of viewpoints to be considered, (2) incorporates the best scientific evidence, and (3) permits sensitivity analyses to evaluate the impact of alternative clinical scenarios and uncertainty in model inputs. The Stroke Prevention Policy Model (SPPM) illustrates this approach. The SPPM is a simulation model designed to predict the best among various treatment alternatives for preventing strokes. Similar models can be applied to treatment outcomes for liver disease.

Performing cost-effectiveness analysis by integrating randomized trial data with a comprehensive decision model: application to treatment of acute ischemic stroke

A recent national panel on cost-effectiveness in health and medicine has recommended that cost-effectiveness analysis (CEA) of randomized controlled trials (RCTs) should reflect the effect of treatments on long-term outcomes. Because the follow-up period of RCTs tends to be relatively short, long-term implications of treatments must be assessed using other sources. We used a comprehensive simulation model of the natural history of stroke to estimate long-term outcomes after a hypothetical RCT of an acute stroke treatment. The RCT generates estimates of short-term quality-adjusted survival and cost and also the pattern of disability at the conclusion of follow-up. The simulation model incorporates the effect of disability on long-term outcomes, thus supporting a comprehensive CEA. Treatments that produce relatively modest improvements in the pattern of outcomes after ischemic stroke are likely to be cost-effective. This conclusion was robust to modifying the assumptions underlying the analysis. More effective treatments in the acute phase immediately following stroke would generate significant public health benefits, even if these treatments have a high price and result in relatively small reductions in disability. Simulation-based modeling can provide the critical link between a treatment's short-term effects and its long-term implications and can thus support comprehensive CEA.

Epidemiology of recurrent cerebral infarction: a medicare claims-based comparison of first and recurrent strokes on 2-year survival and cost

BACKGROUND AND PURPOSE

Because recurrent strokes will tend to leave patients with greater disability than first strokes, patients with recurrent strokes should have poorer outcomes on average than those with first strokes. The extent of this difference has, however, not yet been estimated with precision.

METHODS

Using a random 20% sample of Medicare patients aged 65 years and older admitted with a primary diagnosis of cerebral infarction during calendar year 1991, we used historical data from the previous 4 years to classify patients as having either first or recurrent stroke and followed survival and direct medical costs for 24 months after stroke. First and recurrent stroke groups were compared with the log-rank test (survival) and t test (cost) and also multivariate modeling.

RESULTS

Survival from first stroke is consistently better than that for recurrent stroke: 24-month survival was 56.7% versus 48.3%, respectively. Costs were similar for the initial hospital stay and in months 1 to 3 after stroke. During months 4 to 24 after stroke, total costs were higher among those with recurrent stroke by approximately $375/mo across all patients, with this difference being greatest for younger patients and least for patients aged 80 years or older. Most of the difference in total monthly cost was attributable to nursing home utilization (averaging approximately $150/mo) and acute hospitalization (averaging approximately $120/mo).

CONCLUSIONS

Patients with recurrent stroke have, on average, poorer outcomes than those with first stroke. To be as accurate as possible, clinical policy analyses should use different estimates of health and cost outcomes for first and recurrent stroke.

Utilities for major stroke: results from a survey of preferences among persons at increased risk for stroke

BACKGROUND

Patient beliefs, values, and preferences are crucial to decisions involving health care. In a large sample of persons at increased risk for stroke, we examined attitudes toward hypothetical major stroke.

METHODS AND RESULTS

Respondents were obtained from the Academic Medical Center Consortium (n = 621), the Cardiovascular Health Study (n = 321 ), and United Health Care (n = 319). Preferences were primarily assessed by using the time trade off (TTO). Although major stroke is generally considered an undesirable event (mean TTO = 0.30), responses were varied: although 45% of respondents considered major stroke to be a worse outcome than death, 15% were willing to trade off little or no survival to avoid a major stroke.

CONCLUSIONS

Providers should speak directly with patients about beliefs, values, and preferences. Stroke-related interventions, even those with a high price or less than dramatic clinical benefits, are likely to be cost-effective if they prevent an outcome (major stroke) that is so undesirable.

Physician-reported readiness to change stroke prevention practices

There are a series of possible impediments to the incorporation of new treatment modalities into clinical practice, and any intervention intended to alter practice must consider physicians' motivation and readiness to change. As part of a national survey in the United States, physicians from a variety of specialties were asked whether they were comfortable with, considering changing or expecting to make changes in their screening and treatment practices for a series of eight hypothetical patients at elevated risk of stroke. Readiness to change varied with the type of patient under consideration and with physician specialty, but not with a series of other physician and practice characteristics. Knowledge of physicians' states of readiness to change in combination with data relating to current practices and potential barriers to implementation should aid in targeting educational efforts and in the development of specific interventions to improve stroke prevention.

The value of stroke prevention and treatment

An emerging issue in stroke prevention and stroke treatment is that therapies shown to be effective in clinical trials are not being used or are being used suboptimally. One of many explanations relates to cost, ranging from concerns about inappropriate use of societal resources to more immediate concerns of organizations and individuals about their financial well-being. Assessing the cost impact of a new therapy, and thus the financial incentives faced by decision-makers, is crucial to understanding and influencing real-world treatment decisions. Assessing cost in the context of health benefits is the object of cost-effectiveness analysis. A cost-effectiveness analysis typically compares the new treatment with a less efficacious yet less costly alternative. This article provides a brief overview of the cost implications of stroke and stroke-related treatments. The example of stroke prevention is used to illustrate how to calculate an incremental cost-effectiveness ratio and help clarify what makes a treatment an especially good value. Because stroke is tremendously expensive and because severe strokes are especially expensive, treatments to prevent stroke and to diminish stroke disability are likely to be an excellent value.

Multicenter review of preoperative risk factors for endarterectomy for asymptomatic carotid artery stenosis

BACKGROUND AND PURPOSE

The benefit of carotid endarterectomy is highly dependent on surgical risk. However, little data are available concerning factors affecting the risk of endarterectomy performed for asymptomatic carotid artery stenosis outside the setting of a randomized controlled trial. The purpose of this study was to analyze the impact of potential preoperative risk factors on the frequency of postoperative complications in patients undergoing the operation for asymptomatic disease in academic medical centers.

METHODS

Data regarding postoperative complications were systematically abstracted from the medical records of a random sample of patients who underwent carotid endarterectomy at 12 academic medical centers.

RESULTS

Of 1160 procedures reviewed, 463 (40%) were performed for asymptomatic disease. Postoperative stroke or death occurred in 13 (2.8%), and myocardial infarction occurred in 8 (1.7%). The rate of postoperative stroke or death was lower in asymptomatic patients than in those with a history of cerebrovascular symptoms in a different vascular distribution, but the difference was not significant (1.8% versus 4.2%; P=.21). There were no significant differences in these rates based on race, a history of angina, recent myocardial infarction, chronic obstructive pulmonary disease, hypertension, the degree of stenosis of the contralateral or ipsilateral carotid artery, or the presence of angiographically recognized ulceration, intraluminal thrombus, or siphon stenosis in the ipsilateral vessel (chi(2); P>.05). Postoperative stroke or death was more frequent in women (5.3% versus 1.6% in men; P=.02), in those aged 75 years or older (7.8% versus 1.8% in those younger than 75 years; P=.01), and in those with a history of congestive heart failure (8.6% versus 2.3% in those without a history of congestive heart failure; P=.03). The risk of stroke or death was higher in the 16 patients who had carotid endarterectomy performed in combination with coronary artery bypass surgery than in those who had only endarterectomy (18.7% versus 2.1%; P<.001).

CONCLUSIONS

The overall risk of postoperative stroke or death was nearly twice that reported by Asymptomatic Carotid Atherosclerosis Study (ACAS) investigators in the setting of a clinical trial but was within acceptable guidelines. Women were at higher postoperative risk than men, which supported ACAS findings. Additional high-risk groups were those aged 75 years or older, those with a history of congestive heart failure, and those undergoing prophylactic endarterectomy for asymptomatic stenosis in combination with coronary surgery. Knowledge of these rates may help to better assess an individual's postoperative risk and therefore the anticipated benefit of surgery.

Predicting the cost of illness: a comparison of alternative models applied to stroke

Predictions of cost over well-defined time horizons are frequently required in the analysis of clinical trials and social experiments, for decision models investigating the cost-effectiveness of interventions, and for macro-level estimates of the resource impact of disease. With rare exceptions, cost predictions used in such applications continue to take the form of deterministic point estimates. However, the growing availability of large administrative and clinical data sets offers new opportunities for a more general approach to disease cost forecasting: the estimation of multivariable cost functions that yield predictions at the individual level, conditional on intervention(s), patient characteristics, and other factors. This raises the fundamental question of how to choose the "best" cost model for a given application. The central purpose of this paper is to demonstrate how to evaluate competing models on the basis of predictive validity. This concept is operationalized according to three alternative criteria: 1) root mean square error (RMSE), for evaluating predicted mean cost; 2) mean absolute error (MAE), for evaluating predicted median cost; and 3) a logarithmic scoring rule (log score), an information-theoretic index for evaluating the entire predictive distribution of cost. To illustrate these concepts, the authors conducted a split-sample analysis of data from a national sample of Medicare-covered patients hospitalized for ischemic stroke in 1991 and followed to the end of 1993. Using test and training samples of about 500,000 observations each, they investigated five models: single-equation linear models, with and without log transform of cost; two-part (mixture) models, with and without log transform, to directly address the problem of zero-cost observations; and a Cox proportional-hazards model stratified by time interval. For deriving the predictive distribution of cost, the log transformed two-part and proportional-hazards models are superior. For deriving the predicted mean or median cost, these two models and the commonly used log-transformed linear model all perform about the same. The untransformed models are dominated in every instance. The approaches to model selection illustrated here can be applied across a wide range of settings.

The Stroke Prevention Policy Model: linking evidence and clinical decisions

Simulation models that support decision and cost-effectiveness analysis can further the goals of evidence-based medicine by facilitating the synthesis of information from several sources into a single comprehensive structure. The Stroke Prevention Policy Model (SPPM) performs this function for the clinical and policy questions that surround stroke prevention. This paper first describes the basic structure and functions of the SPPM, concentrating on the role of large databases (broadly defined as any database that contains many patients, regardless of study design) in providing the SPPM inputs. Next, recognizing that the use of modeling continues to be a source of some controversy in the medical community, it discusses the philosophical underpinnings of the SPPM. Finally, it discusses conclusions in the context of both stroke prevention and other complex medical decisions. We conclude that despite the difficulties in developing comprehensive models (for example, the length and complexity of model development and validation processes, the proprietary nature of data sources, and the necessity for developing new software), the benefits of such models exceed the costs of continuing to rely on more conventional methods. Although they should not replace the clinician in decision making, comprehensive models based on the best available evidence from large databases can support decision making in medicine.

Assessing uncertainty in cost-effectiveness analyses: application to a complex decision model

A framework for quantifying uncertainty about costs, effectiveness measures, and marginal 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 approaches, one based on Bayesian inference and the other on resampling. While computationally 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.

Inaccuracy of the International Classification of Diseases (ICD-9-CM) in identifying the diagnosis of ischemic cerebrovascular disease

In administrative databases the International Classification of Diseases, Version 9, Clinical Modification (ICD-9-CM) is often used to identify patients with specific diagnoses. However, certain conditions may not be accurately reflected by the ICD-9 codes. We assessed the accuracy of ICD-9 coding for cerebrovascular disease by comparing ICD-9 codes in an administrative database with clinical findings ascertained from medical record abstractions. We selected patients with ICD-9 diagnostic codes of 433 through 436 (in either the primary or secondary positions) from an administrative database of patients hospitalized in five academic medical centers in 1992. Medical records of the selected patients were reviewed by trained medical abstractors, and the patients' clinical conditions during the admission (stroke, TIA, asymptomatic) were recorded, as well as any history of cerebrovascular symptoms. Results of the medical record review were compared with the ICD-9 codes from the administrative database. More than 85% of those patients with the ICD-9 code 433 were asymptomatic for the index admission. More than one-third of these asymptomatic patients did not undergo either cerebral angiography or carotid endarterectomy. For ICD-9 code 434, 85% of patients were classified as having a stroke and for ICD-9 code 435, 77% had TIAs. For code 436, 77% of patients were classified as having strokes. Limiting the identifying ICD-9 code to the primary position increased the likelihood of agreement with the medical record review. The ICD-9 coding scheme may be inaccurate in the classification of patients with ischemic cerebrovascular disease. Its limitations must be recognized in the analyses of administrative databases selected by using ICD-9 codes 433 through 436.

Influence of projected complication rates on estimated appropriate use rates for carotid endarterectomy. Appropriateness Project Investigators. Academic Medical Center Consortium

OBJECTIVE

To examine specifically the influence of estimated perioperative mortality and stroke rate on the assessment of appropriateness of carotid endarterectomy.

DATA SOURCES/STUDY SETTING

An expert panel convened to rate the appropriateness of a variety of potential indications for carotid endarterectomy based on various rates of perioperative complications. We then applied these ratings to the charts of 1,160 randomly selected patients who had carotid endarterectomy in one of the 12 participating academic medical centers.

STUDY DESIGN

An expert panel evaluated indications for carotid endarterectomy using the modified Delphi approach. Charts of patients who received surgery were abstracted, and clinical indications for the procedure as well as perioperative complications were recorded. To examine the impact of surgical risk assessment on the rates of appropriateness, three different definitions of risk strata for combined perioperative death or stroke were used: Definition A, low risk < 3 percent; Definition B, low risk < 5 percent; and Definition C, low risk < 7 percent.

PRINCIPAL FINDINGS

Overall hospital-specific mortality ranged from 0 percent to 4.0 percent and major complications, defined as death, stroke, intracranial hemorrhage, or myocardial infarction, varied from 2.0 percent to 11.1 percent. Most patients (72 percent) had surgery for transient ischemic attack or stroke; 24 percent of patients were asymptomatic. Most patients (82 percent) had surgery on the side of a high-grade stenosis (70-99 percent). When the thresholds for operative risk were placed at the values defined by the expert panel (Definition A), only 33.5 percent of 1,160 procedures were classified as "appropriate." When the definition of low risk was shifted upward, the proportion of cases categorized as appropriate increased to 58 percent and 81.5 percent for Definitions B and C, respectively.

CONCLUSIONS

Despite the high proportion of procedures performed for symptomatic patients with a high degree of ipsilateral extracranial carotid artery stenosis and generally low rates of surgical complications at the participating institutions, the overall rate of "appropriateness" using a perioperative complication rate of < 3 percent was low. However, the rate of "appropriateness" was extremely sensitive to judgments about a single clinical feature, surgical risk. These data show that before applying such "appropriateness" ratings, it is crucial to perform sensitivity analyses in order to assess the stability of the results. Results that are robust to moderate in variation in surgical risk provide a much sounder basis for policy making than those that are not.

Knowledge of risk among patients at increased risk for stroke

BACKGROUND AND PURPOSE

Patients who recognize their increased risk for stroke are more likely to engage in (and comply with) stroke prevention practices than those who do not. We describe perceived risk of stroke among a nationally diverse sample of patients at increased risk for stroke and determine whether patients' knowledge of their stroke risk varied according to patients' demographic and clinical characteristics.

METHODS

Respondents were recruited from the Academic Medical Center Consortium (n = 621, five academic medical centers, inpatients of varying age); the Cardiovascular Health Study (n = 321, population-based sample of persons aged 65+ years); and United HealthCare (n = 319, five health plans, inpatients and outpatients typically younger than 65 years). The primary outcome was awareness of being at risk for stroke.

RESULTS

Only 41% of respondents were aware of their increased risk for stroke (including less than one half of patients with previous minor stroke). Approximately 74% of patients who recalled being told of their increased stroke risk by a physician acknowledged this risk in comparison with 28% of patients who did not recall being informed by a physician. Younger patients, depressed patients, those in poor current health, and those with a history of TIA were most likely to be aware of their stroke risk.

CONCLUSIONS

Over one half of patients at increased risk of stroke are unaware of their risk. Healthcare providers play a crucial role in communicating information about risk, and successful communication encourages adoption of stroke prevention practices. Educational messages should be targeted toward patients least likely to be aware of their risk.

Primary care physician-reported secondary and tertiary stroke prevention practices. A comparison between the United States and the United Kingdom

BACKGROUND AND PURPOSE

Stroke is a major healthcare problem in both the United States (US) and the United Kingdom (UK). Little comparative data are available concerning how generalist physicians in the two countries approach the management of patients at high risk of stroke.

METHODS

Contemporaneous surveys of random samples of primary care physician-reported stroke prevention practices were performed in the US and UK from 1993 to 1994. The US National Survey of Physician Practices for the Secondary and Tertiary Prevention of Ischemic Stroke included 254 noninternist primary care physicians. The UK Survey of the Care of Patients With Stroke in General Practice obtained responses from 661 general practitioners. The two surveys used many of the same questions, allowing for direct comparisons of reported stroke prevention practices between American and British physicians.

RESULTS

More than 80% of American physicians reported a variety of services (24-hour electrocardiography, echocardiography, brain CT scan, brain MR scan, carotid ultrasonography, cerebral angiography) as readily available. These same services were readily available to less than 10% of physicians in the UK (P < .001 for each comparison). Although physicians in the UK reported prescribing lower doses of aspirin for stroke prevention than physicians in the US, the proportions of physicians using aspirin were not different. In contrast, almost 70% of physicians in the US responded that they always or often anticoagulate patients with nonvalvular atrial fibrillation compared with 7% of British physicians (P < .001). Whereas 70% of American versus 14% of British physicians reported obtaining carotid ultrasound studies in patients with asymptomatic bruits (P < .001), physicians in the UK more commonly reported referring this type of patient to neurologists (46% versus 21%, P < .001). For patients with recent carotid-distribution transient ischemic attack or minor stroke, physicians in the US more commonly reported referral to neurologists (55% versus 45%, P = .022), referral to surgeons (39% versus 19%, P < .001), the performance of carotid ultrasonography (80% versus 11%, P < .001), echocardiography (45% versus 5%, P < .001), 24-hour electrocardiography (49% versus 4%, P < .001), brain CT scan (72% versus 3%, P < .001), and the prescription of anticoagulants (53% versus 4%, P < .001).

CONCLUSIONS

These data show significant differences in stroke prevention practices as reported by primary care physicians practicing in the US and UK. Some of these differences may be related to the relative availability of specific services in the two countries, potentially leading to overutilization in the US and underutilization in the UK in certain circumstances.