Low Fuel Convergence Path to Direct-Drive Fusion Ignition.

A new class of inertial fusion capsules is presented that combines multishell targets with laser direct drive at low intensity (2.8×10^{14} W/cm^{2}) to achieve robust ignition. The targets consist of three concentric, heavy, metal shells, enclosing a volume of tens of µg of liquid deuterium-tritium fuel. Ignition is designed to occur well "upstream" from stagnation, with minimal pusher deceleration to mitigate interface Rayleigh-Taylor growth. Laser intensities below thresholds for laser plasma instability and cross beam energy transfer facilitate high hydrodynamic efficiency (∼10%).

A comparison of approaches for association studies of polymorphisms and colorectal cancer risk.

AIM: Meta-analyses have been used to evaluate associations between polymorphisms and colorectal cancer risk, but the quality of individual studies used to inform them may vary substantially. Our aim was to apply well-established quality-control criteria to individual association studies and then compare the results of meta-analyses that included or excluded studies that did not meet these criteria. METHOD: We used meta-analyses of studies reporting a relationship between polymorphisms and colorectal cancer published between 1996 and 2008. Polymorphism-cancer associations were derived in separate meta-analyses including only those meeting the quality-control criteria. RESULTS: Relative ORs varied substantially between the open and restricted group meta-analyses for all variants except MTHFR 677 CT. However, the associations were modest and the direction of relative risk did not change after applying criteria. Publication bias was detected for all associations, except the restricted set of studies for GSTP1 GG. CONCLUSION: We observed variation in calculated relative risk and changes in tests for publication bias that were dependent on the inclusion criteria used for association studies of polymorphisms and colorectal cancer. Standardizing study inclusion criteria may reduce the variation in findings for meta-analyses of gene-association studies of common diseases such as colorectal cancer.

Patterns of blood product use among patients with myelodysplastic syndrome.

BACKGROUND AND OBJECTIVES: Most patients with myelodysplastic syndrome (MDS) require blood product support to manage the severe anaemias, which frequently accompany MDS. Our objective was to show the feasibility of linking the Surveillance, Epidemiology and End Results (SEER) database with records from Puget Sound Blood Center (PSBC) to characterize blood product use over time in successive cohorts of patients with MDS. MATERIALS AND METHODS: We identified patients with MDS in the SEER registry. The cohort was then linked to PSBC records to discern blood product use. RESULTS: Included in the analysis were 783 patients with MDS entered in the SEER database from 2001 to 2007 for whom data were also available in the PSBC database. Among patients with MDS who received transfusions, 97% received packed red blood cells; 52% received platelets. The proportion of patients with MDS receiving blood products declined from 2001 to 2007. CONCLUSION: These data show a recent decline in blood product use for patients with MDS. Future studies are needed to further evaluate the reasons for this finding, specifically exploring the impact of newer medications on blood product use in patients with MDS.

The burden of illness and economic evaluation for COPD.

In today's cost-conscious environment, understanding the economic implications associated with disease processes and their treatments is as important as understanding their clinical impact. Medical expenditures for treating chronic obstructive pulmonary disease (COPD) and the indirect costs of morbidity can represent a substantial economic and social burden. Very little economic information concerning COPD is available, however, particularly outside of a few very well-developed Western nations. This article will provide an approach for conducting high-quality studies aimed at estimating the economic burden of chronic obstructive pulmonary disease and for making economic evaluations of healthcare interventions aimed at preventing and treating this disease.

The role of hospital volume in coronary artery bypass grafting: is more always better?

OBJECTIVES: The goal of this study was to determine whether outcomes of nonemergent coronary artery bypass grafting (CABG) differed between low- and high-volume hospitals in patients at different levels of surgical risk. BACKGROUND: Regionalizing all CABG surgeries from low- to high-volume hospitals could improve surgical outcomes but reduce patient access and choice. "Targeted" regionalization could be a reasonable alternative, however, if subgroups of patients that would clearly benefit from care at high-volume hospitals could be identified. METHODS: We assessed outcomes of CABG at 56 U.S. hospitals using 1997 administrative and clinical data from Solucient EXPLORE, a national outcomes benchmarking database. Predicted in-hospital mortality rates for subjects were calculated using a logistic regression model, and subjects were classified into five groups based on surgical risk: minimal (< 0.5%), low (0.5% to 2%), moderate (2% to 5%), high (5% to 20%), and severe (> or =20%). We assessed differences in in-hospital mortality, hospital costs and length of stay between low- and high-volume facilities (defined as > or =200 annual cases) in each of the five risk groups. RESULTS: A total of 2,029 subjects who underwent CABG at 25 low-volume hospitals and 11,615 subjects who underwent CABG at 31 high-volume hospitals were identified. Significant differences in in-hospital mortality were seen between low- and high-volume facilities in subjects at moderate (5.3% vs. 2.2%; p = 0.007) and high risk (22.6% vs. 11.9%; p = 0.0026) but not in those at minimal, low or severe risk. Hospital costs and lengths of stay were similar across each of the five risk groups. Based on these results, targeted regionalization of subjects at moderate risk or higher to high-volume hospitals would have resulted in an estimated 370 transfers and avoided 16 deaths; in contrast, full regionalization would have led to 2,029 transfers and avoided 20 deaths. CONCLUSIONS: Targeted regionalization might be a feasible strategy for balancing the clinical benefits of regionalization with patients' desires for choice and access.

Randomized trial of amplification strategies.

BACKGROUND: Little is known about quality of life after the use of specific types of hearing aids, so it is difficult to determine whether technologies such as programmable circuits and directional microphones are worth the added expense. OBJECTIVE: To compare the effectiveness of an assistive listening device, a nonprogrammable nondirectional microphone hearing aid, with that of a programmable directional microphone hearing aid against the absence of amplification. DESIGN: Randomized controlled trial. SETTING: Audiology clinic at the VA Puget Sound Health Care System, Seattle, Wash. PATIENTS: Sixty veterans with bilateral moderate to severe sensorineural hearing loss completed the trial. Half the veterans (n = 30) had hearing loss that the Veterans Affairs clinic determined was rated as "service connected," which meant that they were eligible for Veterans Affairs-issued hearing aids. INTERVENTION: Veterans with non-service-connected hearing loss, who were ineligible for Veterans Affairs-issued hearing aids, were randomly assigned to no amplification (control arm) or to receive an assistive listening device. Veterans with service-connected loss were randomly assigned to receive either the nonprogrammable hearing aid that is routinely issued ("conventional") or a programmable aid with a directional microphone ("programmable"). MAIN OUTCOME MEASURES: Hearing-related quality of life, self-rated communication ability, adherence to use, and willingness to pay for the amplification devices (measured 3 months after fitting). RESULTS: Clear distinctions were observed between all 4 arms. The mean improvement in hearing-related quality of life (Hearing Handicap Inventory for the Elderly) scores was small for control patients (2.2 points) and patients who received an assistive listening device (4.4 points), excellent for patients who received a conventional device (17.4 points), and substantial for patients who received a programmable device (31.1 points) (P<.001 by the analysis of variance test). Qualitative analyses of free-text diary entries, self-reported communication ability (Abbreviated Profile of Hearing Aid Benefit) scores, adherence to hearing aid use, and willingness to pay for replacement devices showed similar trends. CONCLUSIONS: A programmable hearing aid with a directional microphone had the highest level of effectiveness in the veteran population. A nonprogrammable hearing aid with an omnidirectional microphone was also effective compared with an assistive listening device or no amplification.

Cost-effectiveness of microsatellite instability screening as a method for detecting hereditary nonpolyposis colorectal cancer.

BACKGROUND: The National Cancer Institute has published consensus guidelines for universal screening for hereditary nonpolyposis colorectal cancer (HNPCC) in patients with newly diagnosed colorectal cancer. OBJECTIVE: To determine the cost-effectiveness of screening compared with standard care in eligible patients with colorectal cancer and their siblings and children. DESIGN: Cost-effectiveness analysis. DATA SOURCES: National colorectal cancer registry data, the Creighton International Hereditary Colorectal Cancer Registry, Medicare claims records, and published literature. TARGET POPULATION: Patients with newly diagnosed colorectal cancer and their siblings and children. TIME HORIZON: Lifetime (varies depending on age at screening). PERSPECTIVE: Societal. INTERVENTIONS: Initial office-based screening to determine eligibility (based on personal and family cancer history), followed by tumor testing for microsatellite instability. Those with microsatellite instability were offered genetic testing for HNPCC. Siblings and children of patients with cancer and the HNPCC mutation were offered genetic testing, and those who were found to carry the mutation received lifelong colorectal cancer screening. MEASUREMENTS: Life-years gained. RESULTS OF BASE-CASE ANALYSIS: When only the patients with cancer were considered, cost-effectiveness of screening was $42 210 per life-year gained. When patients with cancer and their siblings and children were considered together, cost-effectiveness increased to $7556 per life-year gained. RESULTS OF SENSITIVITY ANALYSIS: The model was most sensitive to the estimated survival gain from screening siblings and children, to the prevalence of HNPCC mutations among patients with newly diagnosed cancer, and to the discount rate. In probabilistic analysis, the 90% CI for the cost-effectiveness of screening patients with cancer plus their relatives was $4874 to $21 576 per life-year gained. CONCLUSION: Screening patients with newly diagnosed colorectal cancer for HNPCC is cost-effective, especially if the benefits to their immediate relatives are considered.

Coronary artery bypass grafting in Native Americans: a higher risk of death compared to other ethnic groups?

BACKGROUND: While the efficacy and safety of coronary artery bypass grafting (CABG) has been established in several clinical trials, little is known about its outcomes in Native Americans. MEASUREMENTS AND MAIN RESULTS: We assessed clinical outcomes associated with CABG in 155 Native Americans using a national database of 18,061 patients from 25 nongovernmental, not-for-profit U.S. health care facilities. Patients were classified into five groups: 1) Native American, 2) white, 3) African American, 4) Hispanic, and 5) Asian. We evaluated for ethnic differences in in-hospital mortality and length of stay, and after adjusting for age, gender, surgical priority, case-mix severity, insurance status, and facility characteristics (volume, location, and teaching status). Overall, we found the adjusted risk for in-hospital death to be higher in Native Americans when compared to whites (odds ratio [OR], 3.8; 95% confidence interval [CI], 1.5 to 9.8), African Americans (OR, 3.4; 95% CI, 1.1 to 9.9), Hispanics (OR, 7.1; 95% CI, 2.5 to 20.3), and Asians (OR, 2.8; 95% CI, 1.1 to 7.0). No significant differences were found in length of stay after adjustment across ethnic groups. CONCLUSIONS: The risk of in-hospital death following CABG may be higher in Native Americans than in other ethnic groups. Given the small number of Native Americans in the database (n = 155), however, further research will be needed to confirm these findings.

Relative impact of patient and clinic factors on adherence to primary care preventive service guidelines: an exploratory study.

BACKGROUND: Preventive care service use is commonly compared across health plans, clinics, or individual providers, yet little is known about the influence of the clinic versus patient factors on utilization of these services. OBJECTIVES: To measure the relative influence of the facility (clinic) versus patient factors (demographic, behavioral and functional characteristics) on patients' utilization of mammography, Pap smears, cholesterol screening, and retinal exams for those with diabetes. RESEARCH DESIGN: Retrospective analysis, using administrative and patient survey data. SUBJECTS: Enrollees in 2 University-based clinics and a county hospital-based clinic serving a predominantly low-income population with limited access to health care. Eligibility for cervical cancer screening, screening mammography, cholesterol screening, or annual retinal exam (diabetes) was defined by age, sex, and diagnosis. MEASURES: Multivariate models, one using readily available administrative data, and another using detailed health status and behavior data gathered from a clinics-wide survey. RESULTS: Unadjusted screening rates for three of four procedures were significantly and substantially lower at the county hospital based clinic than the two University-based clinics. After adjusting for patient characteristics, utilization of three screening services at the county hospital remained significantly below the University-based clinics (Odds Ratios [95% CI]: mammogram 0.15 [0.06-0.35]; Pap smear 0.32 [0.21-0.50]; cholesterol 0.19 [0.09-0.38]; diabetes retinal exam10.68 [0.93-3.01]). The models with detailed survey data performed only marginally better than the models using only administrative data. CONCLUSIONS: Patient characteristics were much less important than the clinic for predicting whether patients received primary care preventive services. Our results suggest that case mix adjustment is unlikely to explain away discrepancies in performance between clinics or provider groups.

Randomized phase III trial of paclitaxel plus carboplatin versus vinorelbine plus cisplatin in the treatment of patients with advanced non--small-cell lung cancer: a Southwest Oncology Group trial.

PURPOSE: This randomized trial was designed to determine whether paclitaxel plus carboplatin (PC) offered a survival advantage over vinorelbine plus cisplatin (VC) for patients with advanced non--small-cell lung cancer. Secondary objectives were to compare toxicity, tolerability, quality of life (QOL), and resource utilization. PATIENTS AND METHODS: Two hundred two patients received VC (vinorelbine 25 mg/m(2)/wk and cisplatin 100 mg/m(2)/d, day 1 every 28 days) and 206 patients received PC (paclitaxel 225 mg/m(2) over 3 hours with carboplatin area under the curve of 6, day 1 every 21 days). Patients completed QOL questionnaires at baseline, 13 weeks, and 25 weeks. Resource utilization forms were completed at five time points through 24 months. RESULTS: Patient characteristics were similar between the groups. The objective response rate was 28% in the VC arm and 25% in the PC arm. Median survival was 8 months in both arms, with 1-year survival rates of 36% and 38%, respectively. Grade 3 and 4 leukopenia (P =.002) and neutropenia (P =.008) occurred more frequently on the VC arm. Grade 3 nausea and vomiting were higher on the VC arm (P =.001, P =.007), and grade 3 peripheral neuropathy was higher on the PC arm (P <.001). More patients on the VC arm discontinued therapy because of toxicity (P =.001). No difference in QOL was observed. Overall costs on the PC arm were higher than on the VC arm because of drug costs. CONCLUSION: PC is equally efficacious as VC for the treatment of advanced non--small-cell lung cancer. PC is less toxic and better tolerated but more expensive than VC. New treatment strategies should be pursued.

Pharmaco-economic impact of HMG-CoA reductase inhibitors in type 2 diabetes.

Dyslipidemia is very common in diabetics and substantially increases the risk of fatal and non-fatal cardiovascular disease. Pharmacological therapy with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors ('statins') is effective for dyslipidemia, but the cost and efficacy of individual therapies vary. Therefore, the interest in cost-effective pharmacologic interventions for the prevention of cardiovascular disease events in diabetics has increased. In this article, the literature pertaining to the epidemiology, cost and efficacy of statins in preventing cardiovascular disease in patients with type 2 diabetes mellitus, in both the primary and secondary prevention settings, is reviewed. Cost-effectiveness studies of statins in the diabetic population are detailed, along with recommendations for further research.

Economic evaluation of systemic treatments for cytomegalovirus retinitis in patients with AIDS.

OBJECTIVE: To determine the cost of using systemic therapy to treat newly diagnosed cytomegalovirus (CMV) retinitis in persons with AIDS. DESIGN: Incidence-based simulation model of CMV treatment from a government payer perspective. SETTING: Swiss healthcare system. PATIENTS AND PARTICIPANTS: Patients with AIDS and newly diagnosed CMV retinitis. INTERVENTIONS: Patients were assigned to 1 of 4 treatment regimens for induction and maintenance therapy: (i) intravenous (IV) cidofovir induction and maintenance (cidofovir IV/IV); (ii) IV foscarnet induction and maintenance (foscarnet IV/IV); (iii) IV ganciclovir induction and maintenance (ganciclovir IV/IV); and (iv) IV ganciclovir induction and oral (PO) ganciclovir maintenance (ganciclovir IV/PO). Following a second relapse, patients were assigned to one of the other regimens. MAIN OUTCOME MEASURES: Time to first and subsequent progression, duration of maintenance treatment and direct medical expenditures [1998 Swiss francs (SwF)] . RESULTS: The median time to first progression was longest for cidofovir IV/IV, followed by foscarnet IV/IV, ganciclovir IV/IV and ganciclovir IV/PO. Mean survival was 13 months and mean costs for this period in the base case were lowest in those initially treated with cidofovir (SwF146,742), followed by initial treatment with foscarnet IV/IV (SwF194,809), ganciclovir IV/PO (SwF195,190) and ganciclovir IV/IV (SwF243,964). Costs were most sensitive to changes in efficacy estimates. CONCLUSIONS: Of the regimens studied, initiation of treatment with systemic cidofovir appears least costly over a 13-month period.

Use of alternative therapies by older adults with osteoarthritis.

OBJECTIVE: To examine the rates of use and expenditures on alternative therapies by adults with osteoarthritis (OA). METHODS: Adults with OA recruited from the community to participate in a randomized clinical trial recorded alternative and traditional health care use on postcard diaries. General and arthritis-specific quality of life was assessed by questionnaires. RESULTS: More than 47% of participants reported using at least one type of alternative care during the 20-week intervention period. Among alternative care consumers, the most commonly used treatments were massage therapy (57%), chiropractic services (20.7%), and nonprescribed alternative medications (17.2%). Four percent of subjects reported using only alternative care during the study period. Expenditures for alternative therapy averaged $1,127 per year, compared with $1,148 for traditional therapies. CONCLUSION: Use of and expenditures for alternative care were high among this cohort of older adults with OA. Clinicians may want to inquire about use of these therapies before recommending treatments for this condition.

Economic evaluation of aquatic exercise for persons with osteoarthritis.

OBJECTIVES: To estimate cost and outcomes of the Arthritis Foundation aquatic exercise classes from the societal perspective. DESIGN: Randomized trial of 20-week aquatic classes. Cost per quality-adjusted life year (QALY) gained was estimated using trial data. Sample size was based on 80% power to reject the null hypothesis that the cost/QALY gained would not exceed $50,000. SUBJECTS AND METHODS: Recruited 249 adults from Washington State aged 55 to 75 with a doctor-confirmed diagnosis of osteoarthritis to participate in aquatic classes. The Quality of Well-Being Scale (QWB) and Current Health Desirability Rating (CHDR) were used for economic evaluation, supplemented by the arthritis-specific Health Assessment Questionnaire (HAQ), Center for Epidemiologic Studies-Depression Scale (CES-D), and Perceived Quality of Life Scale (PQOL) collected at baseline and postclass. Outcome results applied to life expectancy tables were used to estimate QALYs. Use of health care facilities was assessed from diaries/questionnaires and Medicare reimbursement rates used to estimate costs. Nonparametric bootstrap sampling of costs/QALY ratios established the 95% CI around the estimates. RESULTS: Aquatic exercisers reported equal (QWB) or better (CHDR, HAQ, PQOL) health-related quality of life compared with controls. Outcomes improved with regular class attendance. Costs/QALY gained discounted at 3% were $205,186 using the QWB and $32,643 using the CHRD. CONCLUSION: Aquatic exercise exceeded $50,000 per QALY gained using the community-weighted outcome but fell below this arbitrary budget constraint when using the participant-weighted measure. Confidence intervals around these ratios suggested wide variability of cost effectiveness of aquatic exercise.

The impact of including future medical care costs when estimating the costs attributable to a disease: a colorectal cancer case study.

A source of controversy in the economic literature concerns whether to include or exclude future medical care costs when computing attributable costs for lifesaving interventions. Although it is hypothesized that including future medical care costs will offset the cost savings achieved through prevention, the magnitude of the effect is not known. The objectives of the present study are to develop a methodology for estimating the excess costs of care among colorectal cancer patients, including and excluding future costs of care, and comparing these results with previous studies that do not include costs in added years of life. Subjects in the study included those identified with colorectal cancer drawn from the Surveillance, Epidemiology and End Results (SEER)-Medicare database and an age- and gender-matched control group drawn from the general Medicare population. Using the Kaplan-Meier Sample Average estimator, we directly estimate expected 11-year costs, and then, with the addition of some simple extrapolating assumptions, determine expected 25-year costs. The latter time horizon captures lifetime costs for over 90% of the cohort. Males results for discounted, stage-specific 11- versus 25-year excess costs: in situ, 22411 dollars versus 23494 dollars; Stage 1, 29365 dollars versus 32510 dollars; Stage 2, 28114 dollars versus 25263 dollars; Stage 3, 27397 dollars versus 19647 dollars; Stage 4, 3006 dollars versus 7837 dollars. Trends were similar for females. It can be concluded that adding costs of care in future years for those whose colorectal cancer is prevented owing to screening greatly alters the estimate of lifetime excess costs for colorectal cancer patients, and can produce negative results for advanced stage disease. The results emphasize the need to adopt a standard approach for dealing with future costs when evaluating lifesaving interventions for cost-effectiveness analyses.

Economic analysis of lung volume reduction surgery as part of the National Emphysema Treatment Trial. NETT Research Group.

BACKGROUND: In today's cost-conscious health care environment, obtaining timely and accurate economic information regarding new medical technologies has become extremely important. The National Emphysema Treatment Trial, a multicenter, randomized controlled trial of lung volume reduction surgery (LVRS) plus medical therapy, versus medical therapy for patients with severe emphysema, includes a parallel cost-effectiveness analysis. METHODS: The analysis is designed to determine the cost-effectiveness of LVRS versus medical therapy for those who are eligible for the procedure. After describing theoretical foundations of cost-effectiveness analysis as they apply to this study, we describe the economic and quality of life data that are being collected alongside the clinical trial, methods of analysis, and approach to presenting the results. RESULTS: The cost-effectiveness of LVRS relative to medical therapy will be presented as costs per quality-adjusted life years gained. CONCLUSIONS: This analysis will provide timely economic data that can be considered alongside the clinical results of the National Emphysema Treatment Trial. As one of the largest clinical trials to include a parallel, prospective cost-effectiveness analyses, this study will also provide valuable practical information about conducting an economic analysis alongside a multicenter clinical trial.

Design issues for conducting cost-effectiveness analyses alongside clinical trials.

In response to rising demands for timely economic data on new medical technologies, cost-effectiveness studies are increasingly being conducted alongside clinical trials. Because of the historical differences in perspective and methods between cost-effectiveness studies and clinical trials, the design phase of these hybrid trials requires special consideration. Cost-effectiveness studies require more comprehensive evaluations of outcomes than the endpoints typically measured in clinical trials. Often, these comprehensive outcome measures (such as quality of life) prove useful for interpreting the other endpoints measured in the trial, as well as for estimating the cost-effectiveness of the intervention. In this manuscript, we discuss several aspects related to the design of joint clinical/economic trials, including study perspective, hypothesis testing, sample size estimation, and methods for collecting cost and outcome data. We also discuss issues that may limit the external validity of the cost-effectiveness results of these trials. Many potential threats to external validity can be successfully addressed if they are identified and accounted for in the design phase of the study.

Effect of improved glycemic control on health care costs and utilization.

CONTEXT: Because of the additional costs associated with improving diabetes management, there is interest in whether improved glycemic control leads to reductions in health care costs, and, if so, when such cost savings occur. OBJECTIVE: To determine whether sustained improvements in hemoglobin A(1c) (HbA(1c)) levels among diabetic patients are followed by reductions in health care utilization and costs. DESIGN AND SETTING: Historical cohort study conducted in 1992-1997 in a staff-model health maintenance organization (HMO) in western Washington State. PARTICIPANTS: All diabetic patients aged 18 years or older who were continuously enrolled between January 1992 and March 1996 and had HbA(1c) measured at least once per year in 1992-1994 (n = 4744). Patients whose HbA(1c) decreased 1% or more between 1992 and 1993 and sustained the decline through 1994 were considered to be improved (n = 732). All others were classified as unimproved (n = 4012). MAIN OUTCOME MEASURES: Total health care costs, percentage hospitalized, and number of primary care and specialty visits among the improved vs unimproved cohorts in 1992-1997. RESULTS: Diabetic patients whose HbA(1c) measurements improved were similar demographically to those whose levels did not improve but had higher baseline HbA(1c) measurements (10.0% vs 7.7%; P<.001). Mean total health care costs were $685 to $950 less each year in the improved cohort for 1994 (P =.09), 1995 (P =.003), 1996 (P =.002), and 1997 (P =.01). Cost savings in the improved cohort were statistically significant only among those with the highest baseline HbA(1c) levels (>/=10%) for these years but appeared to be unaffected by presence of complications at baseline. Beginning in the year following improvement (1994), utilization was consistently lower in the improved cohort, reaching statistical significance for primary care visits in 1994 (P =.001), 1995 (P<.001), 1996 (P =.005), and 1997 (P =.004) and for specialty visits in 1997 (P =.02). Differences in hospitalization rates were not statistically significant in any year. CONCLUSION: Our data suggest that a sustained reduction in HbA(1c) level among adult diabetic patients is associated with significant cost savings within 1 to 2 years of improvement.

Simulation modeling of outcomes and cost effectiveness.

Modeling will continue to be used to address important issues in clinical practice and health policy issues that have not been adequately studied with high-quality clinical trials. The apparent ad hoc nature of models belies the methodologic rigor that is applied to create the best models in cancer prevention and care. Models have progressed from simple decision trees to extremely complex microsimulation analyses, yet all are built using a logical process based on objective evaluation of the path between intervention and outcome. The best modelers take great care to justify both the structure and content of the model and then test their assumptions using a comprehensive process of sensitivity analysis and model validation. Like clinical trials, models sometimes produce results that are later found to be invalid as other data become available. When weighing the value of models in health care decision making, it is reasonable to consider the alternatives. In the absence of data, clinical policy decisions are often based on the recommendations of expert opinion panels or on poorly defined notions of the standard of care or medical necessity. Because such decision making rarely entails the rigorous process of data collection, synthesis, and testing that is the core of well-conducted modeling, it is usually not possible for external audiences to examine the assumptions and data that were used to derive the decisions. One of the modeler's most challenging tasks is to make the structure and content of the model transparent to the intended audience. The purpose of this article is to clarify the process of modeling, so that readers of models are more knowledgeable about their uses, strengths, and limitations.

Methods for reviewing economic evaluations of community preventive services: a cart without a horse?

PIP: In a health care system with ever-rising demand and limited resources, economic assessment of medical technologies is important for those who make resource allocation decisions that affect the health of populations. Cost-effectiveness analysis (CEA) is the best developed tool available for comparing the relative health benefits for expenditure among a myriad of available health interventions. Although guidelines for systematic reviews of economic evaluations in community prevention presented in the American Journal of Preventive Medicine address the issue of facilitating comparison of programs, other issues that limit usefulness of CEA to decision-makers in the field arise. The issues include availability of studies, poorly developed and inconsistent evaluations, omission of key resources from the CEA in community prevention, and shifts in public awareness, social norms, and technologic improvements. Extensive discussion of these issues is provided in the article. In conclusion, the methods for systematic review of economic evaluations in the American Journal of Preventive Medicine are important steps. However, it is advisable to use caution in applying them.^ieng