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BCC Transbehavioral Outcome Assessments. December 06, 2001. Potential Outcomes. Criterion % of individuals who attain behavior goal Reduction in 30 mortality Woolf, 1999 Clinical Preventable Burden & Cost Effectiveness Coffield et al., 2001 Quality adjusted life years saved (QALYs)
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BCC TransbehavioralOutcome Assessments December 06, 2001
Potential Outcomes • Criterion • % of individuals who attain behavior goal • Reduction in 30 mortality Woolf, 1999 • Clinical Preventable Burden & Cost Effectiveness Coffield et al., 2001 • Quality adjusted life years saved (QALYs) • Net cost of service/QALYs
References • Woolf, S.H. (1999). The need for perspective in evidence-based medicine. JAMA, 282, 2358-2365. • Coffield, Maciosek, McGinnis et al. (2001). Priorities among recommended clinical preventive services. American Journal of Preventive Medicine, 21(1), 1-9.
Which Interventions Work Best? • Woolf recommends systematically comparing the relative effectiveness of interventions in preventing disease outcomes • Treatment of heart disease reduces mortality by 21-33% • Are these treatments more or less likely to prevent death than smoking cessation or exercise?
Policy and Personal Implications • For Policy Makers: Comparisons are important in terms of reducing number of deaths in the population. • For Individuals: Comparisons inform personal choices.
Calculations • Population projections were derived by multiplying the number of deaths potentially preventable by the intervention by the preventable fraction • Preventable fraction=(p[1-RRR])/(RRR+p[1-RRR]) • p=proportion of eligible population that has not received the intervention • RRR=relative risk reduction
Calculations • Reduction of 30 year mortality • Absolute difference between 30 year cumulative probability of death with and without the intervention • Cumulative probability of death was derived from a standard survival calculation for hypothetical cohort of 45-year-old women using annual mortality rates specified in the tables • Cumulative death rates x RRR = 30 year probability of death with the intervention
Comments • Lifestyle changes offer much greater benefits when compared to disease treatments • Offers rough approximation of benefits comparing tobacco cessation versus dietary change or regular exercise
Ratio’s based on Woolf’s data • Exercise/Tobacco Cessation • NNT = 1.78 • Preventable deaths = 1.84 • Lipids/Tobacco Cessation • NNT = 3.77 • Preventable deaths = 2.48 • Lipids/Exercise • NNT = 2.13 • Preventable deaths = 1.35
Limitations • RRRs have wide confidence intervals • All deaths are not equally preventable • Model is binary, but health effects are continuous (e.g., exercise, all benefit) • Assumes complete adherence (unrealistic) • Total deaths after age 25 • Mortality vs. QALYs or CE
Clinically Preventable Burden (CPB) • Proportion of disease and injury prevented if delivered to 100% of the target population • CPB is the product of the burden of disease targeted by the service and its effectiveness • Represented as Quality Adjusted Life Years (QALY)
Cost Effectiveness (CE) • CE=(costs of prevention-costs averted) divided by the QALYs saved expressed in 1995 dollars • 13 services CE existed in published studies • 17 services this was estimated
Ratios based on CPB • Tobacco Cessation/Exercise • CPB ratio = 1.67 • QALYs = 33.03 • Tobacco Cessation/Diet • CPB ratio = 2.50 • QALYS = 63.50 • Exercise/Diet • CPB = 1.50 • QALYs = 1.95
Conclusion • Woolf indicates his model can use QALYs or CE to replace 30-year mortality, and adjust for intensity of intervention • 30-year mortality and clinically preventable burden allow broad comparisons across behavior change outcomes and other treatments for disease • Resulting comparisons are meaningful at policy as well as individual counseling levels