Title: ROLE OF ECONOMIC MODELLING IN A COST-EFFECTIVENESS ANALYSIS
1ROLE OF ECONOMIC MODELLING IN A
COST-EFFECTIVENESS ANALYSIS
- Evaluating the cost-effectiveness of
antimalarials in South Africa - Charlotte Muheki Zikusooka
2INTRODUCTION
- In a world with limited resources, it is
necessary to have methods of determining the best
way to allocate those resources among alternative
uses. - Definition Economic Evaluation is a technique
that was developed by economists to assist
decision-making when choices have to be made
between several courses of action. - There are 4 economic evaluation techniques each
one involves the systematic identification,
measurement and valuation of costs and
consequences / benefits/ outcomes of the
alternatives under review.
3BACKGROUND SOUTH AFRICA
- Malaria in South Africa in 3 out of 9 provinces
- Development of resistance to antimalarials to
Chloroquine (CQ) Sulphadoxine-pyremethamine (SP) - Sky-rocketing malaria cases as a result.
- SP adult dose cost 0.10 compared to AL adult
dose cost 2.50 (at that time) - Policy makers need evidence-based information
showing the effectiveness, costs and
cost-effectiveness of a range of alternatives, in
order to make choices. - Traditional economic evaluation approaches become
inadequate in situations where the measurement of
the impact of an intervention is methodologically
complex.
4MALARIA TRENDS IN KWAZULU-NATAL
5BACKGROUND
- Extended response to the malaria problem,
including improved vector control (using new
insecticide for indoor residual spraying) and
improved management of malaria cases (effective
antimalarial) and IRS in neighboring districts in
Mozambique - Dramatic impact on malaria transmission cases
- To which intervention do attribute the positive
impact? - How do conduct a cost-effectiveness analysis in
this complex situation? - A range of methods were used, but in this
presentation we focus on modelling, using the
decision-tree model
6Economic Modelling
- Modelling a way of representing the complexity
of the real world in a more simple and
comprehensible form - In economic evaluation, modelling is a
systematic quantitative approach for assessing
the relative value of one or more decision
options - The use of models in cost-effectiveness studies
has been increasing over the years despite the
concerns and debates - Decision-analytic models used in economic
evaluation include, decision trees, Markov
models, Monte Carlo (stochastic) simulations, and
Discrete Event simulations. - A decision tree graphically depicts components
of a decision problem and relates actions to
consequences - Markov model is a decision-analytic model that
involves a Markov process, i.e. is a modelling
technique derived from matrix algebra, which
describes the transitions a cohort of patients
make among a number of health states during the
series of short or long cycles
7(No Transcript)
8MARKOV Model - illustration
9COST-EFFECTIVES OF ANTIMALARIALS IN S. AFR
- Comparing SP and ACTs in 2 provinces (KZN MPM)
- A decision tree was used to evaluate and compare
the relative impact on costs and health outcomes
associated with both uncomplicated and severe
malaria - SP monotherapy artemether-lumefantrine (in KZN)
- SP monotherapy Artesunate SP (in MPUM)
- Antimalarial effectiveness
- KZN SP (12) AL (99)
- MPUM SP (95) ASSP (99)
10RESULTS FROM DECISION TREE MODEL
KZN Cost Incr Cost Eff Incr Eff C/E Incr C/E
Treat with AL 18.80 Â 0.9999 Â 18.82 Â
Treat with SP 115.80 97.00 0.9792 -0.0206 118.26 (Dominated)
The strategy "Treat with SP" is dominated by "Treat with AL". The strategy "Treat with SP" is dominated by "Treat with AL". The strategy "Treat with SP" is dominated by "Treat with AL". The strategy "Treat with SP" is dominated by "Treat with AL". The strategy "Treat with SP" is dominated by "Treat with AL". The strategy "Treat with SP" is dominated by "Treat with AL". The strategy "Treat with SP" is dominated by "Treat with AL".
MPUM Cost Incr Cost Eff Incr Eff C/E Incr C/E
Treat with ASP 12.00 Â 0.99987 Â 12.05 Â
Treat with SP 24.00 12.00 0.99882 -0.00105 24.05 (Dominated)
The strategy "Treat with SP" is dominated by "Treat with ASP". The strategy "Treat with SP" is dominated by "Treat with ASP". The strategy "Treat with SP" is dominated by "Treat with ASP". The strategy "Treat with SP" is dominated by "Treat with ASP". The strategy "Treat with SP" is dominated by "Treat with ASP". The strategy "Treat with SP" is dominated by "Treat with ASP".
11RESULTS
- ACTs were clearly more cost-effective relative
to SP monotherapy, in both KZN and MPUM. - Sensitivity analyses of the decision tree model
consistently confirm that ACTs more
cost-effective relative to SP monotherapy even
when the values of different variables are varied
over a wide range of values. - C/E ratios were found sensitive to changes in
some of the variables. - C/E ratio for the SP option is sensitive to
changes in the values of pHosp_SP (i.e. the
probability that a patient who has failed to get
cured with SP (first time) will seek care at a
hospital and will be hospitalised to get second
line treatment). - The lower the value of pHosp_SP, the lower the
C/E ratio and vice versa for the SP option.
12KEY FINDINGS AND LESSONS
- Despite being relatively more expensive, ACTs can
be cost-effective. - ACTs were not only more cost-effective than SP
monotherapy, but also resulted in substantial
cost savings in the Kwazulu Natal and Mpumalanga
contexts. - The finding that ACTs are cost-saving in
Mpumalanga is particularly important in two ways
- SP monotherapy was still highly effective in
Mpumalanga (90) unlike in Kwazulu Natal where
its effectiveness had declined to only 12 - There had been no changes in local vector control
programme in Mpumalanga (as was the case in
Kwazulu Natal) - Similar findings have been reported by others
Sudre, P., J.G. Breman, D. McFarland, and J.P.
Koplan (1992) Wilkins, J.J., N. Valentine, and
K. Barnes (2002) Institute of Medicine of the
National Academies (2004) Coleman, P.G., C.
Morel, S. Shillcutt, C.A. Goodman, and A.J. Mills
(2004)
13ROLE OF MODELLING IN ECONOMICS
- Health outcomes are normally achievable in the
very long run - analysts need to find a method for extending the
evidence of effectiveness to cover the time
interval for which effectiveness could logically
apply - THUS, the need to use modelling in economic
evaluation remains of critical importance - HOWEVER Data needs for economic models are
normally extensive and such data are not easily
available, resulting in the need to rely on
assumptions - ALSO Limitations with how to present more
realistic disease epidemiology and health system
challenges in economic models - POLICY MAKERS the black-box effect of some
models makes their results less acceptable by
policy makers
14FINAL REMARKS
- Economist, epidemiologist, public health
specialists not trained in economic/mathematical
models. - Ability to use modelling techniques in analyses
either requires prior training on these
techniques (which is not always feasible) or
working with specialists in modelling (who
usually do not have any training in diseases). - Results of models are not very much trusted and
accepted by policy-makers and other. - Use of models in disease modelling and economic
evaluations is useful and cannot be completely
avoided. - How can modelling techniques be improved and made
more accessible to non-mathematicians?
15THANK YOUfor YOUR ATTENTION