临床经济学评价

1、Tools for Decision Making,Economic evaluation of Health Interventions Shi Rong Shanghai Jiao Tong University,PART I.Opportunity cost,To make a choice means opt for something and give up another opportunity. = Every choice involves a cost. The economists use the term of opportunity cost to emphasis t

2、his cost. Opportunity cost: the best alternative foregone.,Example,You have 1,000 You have 3 options: A/EPI 15 lives saved B/DOTS 20 lives saved C/Fluconazol 5 lives saved What is the opportunity cost of choosing (1) A, (2)B and (3) C?,Marginality : the question is not “ to study or not ”, but “how

3、many hours per course”? Hours in study Result 5 20/100 10 50/100 15 70/100 20 80/100 25 85/100 30 86/100,Marginality for the consumer,It depends also on the quantity I have already! Before buying/consuming one unit, I consider what utility brings this supplementary unit. Economists considers that ma

4、rginal utility is decreasing: the next unit brings less utility than the previous one.,Choice: the example of the MoH,In many situations, decision is not on my own resources along my own preferences. Example: Must the MoH put its next $ in condoms, drugs for opportunistic diseases or ARV? How to com

5、pare marginal benefit and marginal cost? = Cost-effectiveness study!,PART .COST ANALYSIS,1. The use of cost information,4 reasons to study costs: to plan a budget and stay within in (accountable); to compare efficiency of different facilities (to identify opportunities of rationing); to fix prices o

6、f a service (allocate cost to goods and services produced); to prioritize between different interventions. = A vital managerial tool!,2.The relation between cost and output: a few definitions,Output: goods or services produced by a firm. Fixed costs: cost incurred once you start a specific productio

7、n, but which is not related to the quantity of output. Variable costs:directly related to the quantity of output.,A few definitions,Total cost: for a given output, FC + VC; It is determined by the current state of technique for the 2nd year: 1 / ( 1 + 0.05)2 = 0.9070; for the 3rd year: 1 / (1 + 0.05

8、)3 = 0.8638; and so on.,Discounting: the formulas,Formula for one year: NPV ( Ci ) = Ci * discount factor if the cost is incurred at the end of the year, the discount factor is 1 if the cost is incurred at the beginning of the year, the discount factor is,( 1 + )i,( 1 + )i-1,1,Discounting: the formu

9、las,Formula for a series of future costs: if the cost is incurred at the end of the year, NPV ( Ci ) = if the cost is incurred at the beginning of the year, NPV ( Ci ) = ,n,n,i=1,n,Ci,(1 +)i,n,i=1,Ci,(1 + )i-1,Example,If, we have 3 years, with C1 = 20, C2 = 30 and C3 = 50, then the formula NPV ( Ci

10、) = becomes NPV ( C ) = + + (cost incurred at the beginning of the year),n,n,i=1,Ci,(1 + )i-1,20,(1+)0,(1+)1,30,(1+)2,50,Exercise,What is the NPV of each distribution of costs? ( = 0.06, costs at the beginning of the year) 2004 2005 2006 2007 Option 1 100 200 300 400 Option 2 500 300 200 0 Option 3

11、0 0 0 1000,Discounting with tables,Tables exist. In the table, N starts at 1. l = next year if the cost is incurred at the beginning of the year; l = this current year, if the cost is incurred the end of the year.,What is the social rate of time preference?,In developed countries, economists use a d

12、iscount rate between 3 and 5 %. In developing countries, the discount rate must be higher (“higher urgency of needs”): the World Bank uses a rate around 10%. Local real interest rate (i.e. inflation taken away ) can also be used as the social discount rate = = r.,Exercise,What is the actualized cost

13、 of this program?(=10%; costs assumed as incurred at the beginning of the years),Sensitivity analysis,This proceeds by: identifying uncertain parameters, drawing up the most realistic range of values for them, inserting these into the final calculation of costs and benefits, considering the effect o

14、f changing the values on the final outcome.,Consequences,If the final value of the decisional criterion is significantly altered and the value of the variable is genuinely uncertain,the conclusion will be shown to be weak by such sensitivity analysis. If the sensitivity analysis shows that the final

15、 value remains quite the same, the conclusion is reinforced.,Example: costs of 2 programs,Discount rate 3% 5% 10% 1800 usd (year 10) 1550 usd (year 5) Choice?,PART . COST-EFFECTIVENESSANALYSIS,The best use of scarce resources Content of this session: Cost benefit Analysis Cost effectiveness Analysis

16、 exercise Cost utility Analysis Other criteria than efficiency,1st Proposal: Cost-Benefit Analysis,“Investing 1 million in intervention X will yield a social benefit of 1,2 million”. “The same amount in intervention Y will yield a social benefit of 1,1 million”. “The same amount in intervention Z wi

17、ll yield a social benefit of 0,9 million”.,1st Proposal: Cost-Benefit Analysis,CBA: method of economic evaluation where the monetary value of the resources consumed by a health intervention (costs) is compared with the monetary value of the outcomes (benefits) achieved by the intervention. Method us

18、ed for damp, highway, tunnel ,CBA,Great quality: the numerator and nominator are in the same unit. = It is possible to compare all the public intervention. Ex: is it better to build a bridge, use the same budget for education or for the control of a disease. Drawback: many outcomes are difficult to

19、value in monetary terms.,How to compare benefits to cost?,The net benefits: Total Benefits Total Costs of an intervention. Intervention relevant if Net Benefit 0 Benefit Cost Ratio: Total Benefit / Total Costs Intervention relevant if BCR 1,Example,Benefit Costs Net BCR (NPV,) (NPV,) Benefits Option

20、 1 4,500 5,000 -500 0.9 Option 2 4,500 3,600 900 1.25 Option 3 45,500 36,000 9,000 1.25,Health benefits in monetary value?,How to give a monetary value to the benefits brought by an intervention? There are 3 types of benefits: direct:savings in future costs of prevention,treatment, control which wou

21、ld be incurred by the health service or patients or society at large. indirect: avoided costs in terms of production or productivity losses. intangible: avoided costs in terms of loss of quality of life.,Indirect benefit,How to value in money terms the years / quality of life saved by an interventio

22、n? “Life has no price” but it has an opportunity cost! Better to save a baby, an adult or an eldery?,Which monetary value for life?,Ask to users themselves: Willingness To Pay Survey. “Ask” to the market (other!): valuation of the life of somebody according to his return to the society = Human Capit

23、al: salary “Ask” to the politicians: study the revelead preferences in political decisions.,To summarize,Too ambitious for health intervention. Good method when the indirect costs are an important part of the problem for the society.Example: a disease which generate many production losses. It is the

24、 only relevant method if you want to compare an intervention in health and an intervention in another sector (cation).,2nd Proposal: Cost-Effectiveness,“Investing 1 million in intervention X will allow to vaccinate 123,000 children”. “With the same amount, intervention Y may finance 1,931,000

25、 malaria chloroquine treatments”. “The same amount in intervention Z will prevent 76,000 prematured deaths”.,2nd Proposal: Cost-Effectiveness,Effects are measured in non monetary values, Natural units. Principle: we have to identify the effect we want to study. For example, to compare two strategies

26、 of vaccination, we will compare cost per child completely vaccinated. It is not always easy to chose!,Breast Cancer Screening: Which cost to minimize?,Screening cost / screened woman? Screening cost / positive case detected? Scr. Example:QWB 3 / For a disease, one estimates the number of years in e

27、ach category of “health status” and we can apply the weight.,The Global Burden of Diseases,Exercise done jointly by the WHO and the WB to identify the diseases having the highest burden on the World (WDR 1993）。 They have used a measure easier than QALYs: international DALYs (Disability Adjusted Life

28、 Years). Application to 107 health disorders, distinction per continent and gender.,A few figures (WHO 2000),Total lost DALYs in 1999:1438 bilions. 66% of DALYs are lost because of a premature death, 34 % because of individuals. Diarrhoea + childhood & perinatal diseases + malaria + RTI = 26.1% Afri

29、ca (10% of world population): 26 % of lost DALY s.,Measuring gains,QALYs and DALYs are different mathematical transformations measuring health outcome. They combine the change in quality of life and the change in life expectancy caused by an intervention, Suppose a medicine allows a patient to live 5 more years but only in a state of health that is considered half as good as a perfect health. Then the gain is 5 *5 = 2.5 QALEs,Cost Utility Analysis,For a given interventi