1,000 word essay aligned with the Drummond checklist critiquing the quality of the assigned article
Lack of Transparency and Quality Barriers to Modeling Utilization
Modeling Challenges
· Does not always lead to choices that maximize public health and limited resources
· Is complicated and not as easily understood as traditional randomized clinical trials
· Represents a relatively new field
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Questions for the
Decision-Makers
· Are the results helpful?
· Are the methods appropriate?
· Are the results valid?
· Do valid results apply to my decision context?
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Transparency
· Indicates compliance with established quality standards
· Refers to clear description of the model structure, equations, parameters, and assumptions
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Transparent Documentation
· Lay summary, accessible to any interested reader
· Model type and intended application; funding sources; model structure; model inputs, outputs, and components; and validation methods, results, and limitations
· Detailed technical document, allowing expert evaluation and potential recreation
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While meeting technical and lay reporting guidelines does not ensure that the model is correct, validation is not possible without a clear understanding of the model.
Defining a Study Question, Perspective, and Scope
What's a Good Question?
· Is well defined and in answerable form
· Clearly identifies the alternatives being compared
· Identifies the perspective from which the comparison is made
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Examples of Bad Questions when alternative is specified
· Is an active PE policy intervention worth it?
· Will a smoking-cessation intervention do any good?
· How much does it cost to run our syringe-exchange program?
· What are the costs and outcomes of the school wellness policy?
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Quality Checklist
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Quality Dimension |
Good Practice Attributes |
Critical Appraisal Questions |
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S1: Statement of decision problem/objective |
• A clearly stated decision problem |
• Is the decision problem clearly stated? |
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• A defined evaluation and model objective |
• Is the evaluation and model objective specified and consistent with the decision problem? |
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• A clearly stated primary decision-maker |
• Is the primary decision-maker specified? |
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S1: Statement of scope/perspective |
• A clearly stated model perspective (relevant costs and consequences) and model inputs consistent with the stated perspective and overall model objective |
• Is the model perspective stated clearly? Are the model inputs consistent with the stated perspective? |
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• A specified and justified decision model scope |
• Is the model scope stated and justified? |
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• Model outcomes that reflect its perspective and scope and are consistent with the objective |
• Are the model outcomes consistent with its perspective, scope, and overall objective? |
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A Good Question
From the perspective of (a) both the Ministry of Health and the Ministry of Community and Social Services budgets and (b) patients incurring out-of-pocket costs, is a chronic home care program preferable to the existing program of institutionalized, extended care in designated wards of general hospitals?
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Study Perspective
· May be a deciding factor of comparative cost-effectiveness
· Should justify any departure from societal perspective and explain any expected impacts on results
Description of Alternatives and Effectiveness Estimates
Comprehensive Description
· Should be provided for each competing alternative
· Who did what to whom, where, and how often
· Helps readers judge relevance to a given setting
· Allows readers to detect cost or consequence omissions
· Provides enough information for program duplication
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Proper Inclusion
· Represents the full range of potential alternatives
· Covers all feasible and practical options, regardless of data availability
· Includes any extendedly dominated options
· Explores the appropriateness of a "do nothing" option
· Compares to the current practice if only one comparison is made
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Effectiveness Estimates
· Are valid effectiveness estimates included for each alternative?
· Are the estimates convincing?
· Is the evidence produced by a single study?
· Does it represent the field's broader evidence?
· Did the authors justify use of a single source?
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Systematic Review
· Helps demonstrate the evaluation's effectiveness
· Thoroughly covers underlying methods, even if cited from previous works
· Evaluates causal inference from quasi-experimental or observational data
· Avoids reliance on randomized controlled trial data for effect size
Measurement and Valuation of Costs and Consequences
Phases of Costing
· Studies often conduct identification, measurement, and valuation simultaneously.
· Quality evaluation considers each step separately.
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Identification
· Was the full range of costs and consequences included?
· Could an expert assess the completeness?
· Were all the relevant perspectives covered?
· Were both capital and operating costs included?
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Measurement
· Were the resource utilization sources described and justified?
· Were any identified items omitted?
· Were there any special circumstances that complicated measurement?
· E.g., overhead costs paid from shared resources
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Valuation
· Were sources identified for all values?
· Were approximations made for any absent market values (as for volunteer labor)?
· Were consequences valued appropriately for the question (e.g., conversion of health effects to monetary value for cost-benefit analyses)?
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Valuation (cont.)
· Were measurement-strategy-related variations in health state valuation described and justified?
· State-to-preference mapping method
· Preference elicitation details
· Were costs and consequences discounted to their present value? Were the discount rates justified?
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Incremental Analyses
· Were the comparisons properly chosen?
· Were both strongly dominated and extendedly dominated alternatives included?
· Were the calculations for the final, best incremental cost-effectiveness ratio well documented?
Description of Uncertainty Analyses
Patient-Level Costs
and Consequences
· Were appropriate statistical analyses performed?
· Were the proper distributions used?
· How were missing data addressed?
· Were alternative statistical techniques used to accurately model the incremental cost-effectiveness ratio uncertainty from trial data?
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Parameters
· Were all of the uncertain parameters identified?
· Were parameters with no assumed uncertainty identified?
· Was any lack of uncertainty justified (e.g., known with absolute certainty)?
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Specifying Uncertainty
· If an arbitrary range of plausible values was used for important parameters, was empirical justification provided for it and the distribution shape?
· Were easy-to-fit distributions (e.g., triangular) with limited statistical justification used?
· Was unavoidable lack of uncertainty evidence for any important variable clear in results discussion?
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Sensitivity Analyses
· Was justification made for any departure from a probabilistic approach?
· If a probabilistic approach was used, was there an analysis of the expected value of perfect information?
· Did the study use any other forms of sensitivity analyses (e.g., scenario analyses on model uncertainty)?
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Reporting Sensitivity Results
· Were the main results sensitive to the sensitivity analyses results?
· Was heterogeneity within subgroups assessed?
· Implications for generally cost-ineffective interventions with potential value for high-risk groups
· Important for evaluating an intervention's potential health disparities effects
Reference Case and Reporting Guidelines
Importance of Reference Case
· Necessary for critical review of economic evaluations
· Foundation upon which modern methodological advice is built
· Considered standard practice
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Why Use a Reference Case?
· Lack of transparency and quality are barriers to utilization of economic evaluation studies.
· Transparency for lay and technical audiences helps ensure quality.
· The wide range of underlying assumptions used in modeling studies is a barrier to assessing quality.
· For comparisons of different studies of the same intervention to be meaningful, the methodologies underlying the results are comparable.
· Prescriptive reporting guidelines aid in transparent communication.
· Agreed-upon preferred analytic methods are needed.
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Why Use a Reference Case? (cont.)
· The elements should be included in every analysis.
· This still allows analysts to report alternative results using different methods while promoting comparability in the field.
· The reference case developed by the U.S. Public Health Service Panel on Cost-Effectiveness in Health and Medicine is a guiding document.
· A second panel will be updating these guidelines in 2016 after 20 years of use in the field.
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Core Element 1: Societal Perspective
The societal perspective should be adopted.
· Taking a narrow perspective that includes either healthcare system or patient costs and outcomes may not adequately capture the costs and outcomes of a health-promotion intervention.
· Societal perspective captures:
· All benefits and harms of the intervention in the outcome, even if they do not accrue to the intended recipients
· The costs of all resources, regardless of who pays and even if no money changes hands
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Core Element 2: Benefits and Harms
Effectiveness estimates should incorporate benefits and harms.
· Corollary to societal perspective
· Narrowly considering only the benefits to target population could ignore harms to others.
· Example: Folic acid fortification potentially masking pernicious anemia in elderly populations
· An intervention can have unintended negative consequences for a group that was not the intended target.
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Core Element 3: QALYs
Mortality and morbidity consequences should be combined using quality-adjusted life years (QALYs).
· Example of hypothetical cancer therapy
· Ignoring health-related quality of life (HRQoL) by focusing narrowly on life years obscures critical information on treatment effectiveness.
· Use of disability-adjusted life years (DALYs) widely accepted
· Analysts may consider reporting both QALY and DALY results when feasible.
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Core Element 4: Sources
Effectiveness estimates from best-designed and least-biased sources should be used.
· This highlights the importance of causally strong systematic review and meta-analysis techniques in the field.
· The utility of trial-based evaluations is limited if the effectiveness results deviate widely from the best evidence in the broader field.
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Core Element 5: Costs
Costs should include healthcare services, patient and caregiver time, and costs of nonhealth impacts.
· This is closely related to the adoption of the societal perspective.
· It is important to capture the costs from all of these sectors.
· Costs should be reported separately to help identify barriers to adoption of cost-effective interventions.
· Who pays is not always (or often not) who benefits from public health interventions.
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Core Element 6: Comparison
Comparison should be made with existing practice and, if necessary, a viable low-cost alternative.
· Comparison to current practice directly relates to the decision context, but may be misleading if current practice is based on ineffective or expensive interventions.
· Anything will look cost-effective if compared to a sufficiently bad alternative.
· Status quo bias should not require us to limit the consideration of alternatives to current bad practice.
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Core Element 7: Discounting
Discounting of costs and health outcomes should be undertaken at a real rate of 3% per year (with 5% as an alternative scenario).
· Debate continues about the "best" discount rate as well as whether health and cost outcomes should discounted at the same rate.
· But there is general consensus on uniform discount rates.
· Using a reference discount rate is critical for comparability.
· Rate may vary based on different decision-making contexts.
· Analyses should include the reference rate for broader comparability.
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Core Element 8: Sensitivity
One-way and multiway sensitivity analysis should be undertaken for important parameters.
· Guideline replaced by the general practice of conducting probabilistic sensitivity analyses
· Limits of using one-way or even multiway sensitivity analyses noted
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Core Element 9: ICER
Comparison of the ICER should be made with those for other relevant interventions.
· Broadly applicable
· Requires consideration of the most relevant alternative
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Reporting Guidelines
· Consolidated Health Economic Evaluation Reporting Standards (CHEERS) Task Force
· Developed to be consistent with CONSORT methodology for reporting results from clinical trials
· Are largely consistent with guidelines previously reviewed
· Contain additional detail on reporting economic evaluations within context of clinical study, as opposed to when using decision-analytic model
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Reporting Guidelines (cont.)
· National Institute of Health and Care Excellence (NICE)
· Ensure minimum methodological standards
· Improve comparability across submissions
· World Health Organization (WHO)
· Used extensively outside of Europe and North America
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ISPOR Guidelines
International Society for Pharmacoeconomics and Outcomes Research
· ISPOR has more than 30 sets of guidelines and continues to provide additional guidance.
· These guidelines are:
· "Official" (i.e., intended for making reimbursement decisions)
· Technical guidance for academics to improve the quality of research
· ISPOR collaborated on a task force with the Society for Medical Decision Making, issuing a series of articles on Modeling Good Research Practices that update the technical aspects of the original reference case guidance.
Model Validation Principles
Importance of Transparency
· Clearly describes the model structure, equations, parameter values, and assumptions
· Enables interested parties to understand the model
· Establishes foundation upon which model evaluation is based
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ISPOR Task Force Reporting
International Society for Pharmacoeconomics and Outcomes Research (ISPOR)-SMDM
· Transparency and validation are required components of full model evaluation.
· Validation is subjecting the model to tests, such as comparing model results with events observed in reality.
· If transparency helps readers understand what a model does and how it does it, validation is the only way for readers to determine how well it works.
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Multiple vs. Single Application Models
· The effort put into building a comprehensive model of disease epidemiology and related health and healthcare costs makes using the same model to evaluate multiple interventions attractive if only to realize some economy of scale.
· More importantly, using the same model to evaluate a range of interventions provides a level methodological field so that variation in ICERs across interventions should be due primarily to intervention-specific inputs and assumptions instead of variation in underlying modeling approaches.
· For these types of models, there is a distinction between validation focused on underlying methods and validation of a specific application of the model.
· Because there is no set of criteria that makes a model "valid," the concept of validation should apply to the specific application, not to the model itself.
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Five Types of Validation
1. Face validity
2. Verification (or internal validity)
3. Cross-validity
4. External validity
5. Predictive validity
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Face Validity (cont.)
· Was once a core component of validation in scale development
· It has fallen out of the nomenclature given its subjectivity.
· ISPOR-SMDM notes that as currently practiced, peer review is insufficiently consistent to be relied on for determining face validity.
· Included in current best practice recommendations, despite limitations
· Should include description of process
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Verification
· Also called internal validity, consistency, or technical validity
· Is a two-step process:
· Verifying individual equations
· Verifying accurate implementation in code
· Should be aligned with best practices in software development
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Cross-Validation
· This is also called external consistency.
· This involves:
· Examining different models that address the same problems and comparing the results
· Examining the differences and their causes
· If different models are highly dependent (i.e., use parameters from other models), the value of cross-validation decreases.
· Modelers should:
· Search for modeling analyses of the same or similar problems
· Discuss insights gained from similarities and differences in results
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External Validation
· Compares a model's results to actual event data
· Involves simulating events that have occurred, often from a clinical trial
· Could apply to the model as a whole or to components such as:
· Population creation
· Disease incidence
· Disease progression
· Outcome occurrence
· Intervention effects
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Calibration: Subcomponent of
External Validation
· In a modeling context, refers to ensuring that inputs and outputs are consistent with available data
· Is important for unobservable intermediate parameters
· Commonly, matches output to external data and adjusts model parameters to achieve a fit with known outcome
· Should include in reporting
· Target
· Goodness-of-fit metric
· Search algorithm
· Acceptance criteria
· Stopping rule
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Predictive Validation
· Involves:
· Identifying an opportunity in which a study design can be well-specified and simulated while reporting the outcome before the outcome occurs
· Comparing the predictions to what actually happened
· Is an important test for multiple-use models that are attempting to inform a broad set of specific applications
· Can be most easily done based on well-reported clinical trial designs that are reported before results are released
· Is much harder to achieve in health-promotion interventions
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Evaluating Validation
Users of models should examine validation results for:
· Rigor of the process
· Quantity and quality of sources used
· How well sources represent model's proposed use
· Model's ability to simulate sources in appropriate detail
· Closeness of results to observed outcomes
Priority-Setting Principles
Complex Global Context
· Growing evidence of poor use of limited health resources
· Rising healthcare expenditures
· Increasing doubts about "free" market as the mechanism for health resource allocation, access to health/health outcomes
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Priority Setting
· Attempts to maintain the clear benefits of economic evaluation by incorporating other resource-prioritization approaches
· Is a recognized field that deals with rationing, but lacks consensus on best methods
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Models of Priority Setting:
Normative Advice
· Behavioral science (achieving consensus)
· Epidemiologists/clinicians (needs assessment)
· Philosophers (social justice)
· Economists (efficiency)
· Administrators (feasibility, historical allocation)
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Choosing From Conflicting
Normative Advice
Assessing Cost-Effectiveness (ACE) framework (Rob Carter et al.) is the basis of an "ideal" approach to priority setting.
· Economic theory: guidance on choices amidst resource scarcity
· Ethics: standards for judging societal welfare
· Empirical evidence and user considerations for relevance
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Economic Theory
· Provides theoretical rationale for better-to-worse alternative ranking
· Bases rank on an allocative efficiency assessment reflective of societal values
· Overlaps with ethics definition of societal welfare
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Economic Approaches
· Welfare economics: favors individual preferences and role of the market
· Extra-welfarism: is health-based, conducive to government intervention and judgment by health professionals
· Decision-making approaches (DMA): focus on the decision-maker as arbiter
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The welfarist focus on individual utility and the extra-welfarist focus on health needs should be supplemented with information on other social concerns, such as need, health status, equity, and procedural justice.
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Ethics and Social Justice
· Like economics, uses logical argument with explicit assumptions
· Unlike welfarism, sometimes rejects the role of community preferences in moral judgments
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Ethical Approaches
· Deontology: duty, process, and individual rights
· Consequentialism: outcomes and collective good
· Distributive justice: impartial, fair balance of competing individual claims
· Combination based on background, experience, and choice problem and setting
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Empirical Experience
· Is commonly used but not as a purely technical approach
· Values efficiency but not at the expense of other objectives
· Strives to balance economic techniques and decision rules with due process and consultation
· Suffers from technical barriers (e.g., lack of data), can limit scope
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User Considerations
· Aims to deliver services to people who will benefit
· Creates guidelines for matching patients to treatment types and intensity levels
· Focuses on evidence-based clinical and public health practices rather than efficiency-based care rationing
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What Is the Best Approach?
While decision-making approaches cannot ignore economic evaluation, policy makers and the public reject those which rely exclusively upon it.
ACE Prevention Priority Setting Example
ACE Prevention Study
· In 2010, the Assessing Cost-Effectiveness (ACE) in Prevention study issued a final report of five-year effort to evaluate cost-effectiveness of prevention investments in Australia.
· Funded by Australian National Health and Medical Council
· Led by Theo Vos and Rob Carter of University of Queensland and Deakin University
· Developed to address the challenges of aging population.
· With consideration of increasing budget pressures
· With a focus on identifying best values in prevention
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ACE Prevention Study (cont.)
· Focused on achieving a more efficient and fairer prevention system
· Addressing deep health inequalities facing indigenous Australians
· Allocating prevention resources to reduce inequities
· Was the largest and most rigorous evaluation of preventive strategies at the time
· Is still a model for using economic evaluation to develop broad health-promotion prioritization strategies
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ACE Prevention Study: Details
· Evaluated 123 prevention interventions and 27 treatment interventions
· Adapted the general population model to evaluate the cost-effectiveness of 21 interventions specifically for indigenous population
· More than doubled the total number of economic evaluations of health promotion and illness prevention in Australia
· Placed results in broader priority-setting context by:
· Getting guidance from stakeholders in government, health nongovernment organizations, academia, and service providers
· Having stakeholders help formulate conclusions by combining technical results with other policy-relevant considerations such as acceptability, feasibility, and equity
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Findings: Impact
Large impact on population health could be achieved with a limited number of cost-effective interventions.
· Taxation of tobacco, alcohol, and unhealthy foods
· Regulation of sodium in bread, cereals, and margarine
· Improving efficiency of blood pressure and cholesterol-lowering drug prescription
· Gastric banding for severe obesity
· Intensive sun-exposure-prevention campaign
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Findings: Second-Stage Filters
Technical findings were combined with second-stage filter considerations.
· The evidence varies.
· "Likely" for taxation and regulation
· "Sufficient" for treatment interventions
· "Limited" for sun-exposure campaign
· Taxation and regulation have low implementation costs but high political costs.
· Proposed changes to blood pressure and cholesterol prescribing have challenges to stakeholder acceptability.
· Government subsidies for gastric banding requires additional guidelines on best practices.
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Findings
· 43 were either cost-saving or cost less than $10,000 per DALY prevented.
· These should only be ignored if there were serious reservations about the evidence base or insurmountable problems related to acceptability or feasibility.
· 31 provided good value compared to a threshold of $50,000 per DALY prevented.
· 38 were expensive compared to the threshold of $50,000 per DALY prevented.
· Of these, four had insufficient evidence, two were associated with more harm than benefit, and two were dominated by more cost-effective alternatives.
The authors concluded that prevention interventions are not always good value and are not always better than treating disease.
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Separate Indigenous Analysis
· Conducted because of differences in many key evaluation parameters
· Target disease burden
· Prevalence and distribution of harmful exposures
· Effectiveness of intervention strategies
· Models of health service delivery
· Acceptability to stakeholders
· Cost of implementation
· Identified meaningful differences in population's health priorities
· Community health gain
· Cultural security
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Recommendations
· Increase tax on tobacco by 30%.
· Change to volumetric tax on alcohol.
· Implement 10% tax on unhealthy foods.
· Enact mandatory regulation of salt in bread, margarine, and cereal.
· Disinvest in prevention activities found to be not cost-effective, including:
· Current cardiovascular preventive treatment
· PSA testing for prostate cancer
· Aspirin for primary prevention of cardiovascular disease
· Most approaches for promoting fruit and vegetable intake and weight-loss programs
· School-based illegal drug interventions