Enhancing the rational use of antimalarials: The cost-effectiveness of rapid immunochromatographic dipsticks in sub-Saharan Africa

Malaria Diagnosis Current practice – presumptive treatment (WHO,1999) ACTs are expensive Misdiagnosis Rapid dipstick tests are being developed for simple diagnosis WHO (1996) IMCI Information Package

Study Questions At what levels of malaria prevalence is dipstick diagnosis cost-effective? How much should we be willing to pay for further information about model parameters before making a decision?

Simple decision tree model Sensitivity Specificity PT: 100% 0% 0% 100% Dip: 86-94% 6-14% 72-99% 1-28%

Probabilistic sensitivity analysis Uncertainty around most parameters represented by lognormal and beta distributions Incremental cost-effectiveness ratios (ICERs) calculated probabilistically using Monte-Carlo simulation ICERs converted to net-benefit Net Benefit = Effects * λ – Costs The ceiling ratio (λ) is US $150 per DALY averted (WHO, 1996) WHO (1996) Report of the Ad Hoc Committee on Health Research Relating to Future Investment Options

Probability Cost-Effective Ceiling Ratio = $150/DALY averted This is where a large graphic or chart can go.

Incremental Net-benefit This is where a large graphic or chart can go.

Calculation of EVPI Ceiling Ratio = $150/DALY averted Iterations Net Benefit Dipsticks Net Benefit PT Net Benefit WPI 1 $40 $20 2 $25 3 $35 4 $30 Average $32.50 EVPI = $32.50 - $30 = $2.50

EVPI according to prevalence This is where a large graphic or chart can go.

Discussion Cost-effectiveness most sensitive to Further benefits Epidemiological setting Cost and accuracy of dipsticks Probability patients return for treatment Further benefits Reduce drug pressure and development of drug resistance Encourage use of treatment facilities Epidemiological surveillance

Limitations of the model Assumes that health workers and patients trust and follow dipstick results False positive diagnoses are not well defined Does not consider private sector Not applicable in areas where microscopy is currently in use EVPI depends on number of variables you include in your model

Further work Conduct a EVSI analysis to determine which parameters warrant further testing Consider parasite density, immunity, and health worker behaviour Determine affordability of dipsticks at a national level Predict impact on drug resistance

Acknowledgements Chris Whitty Sarah Staedke Shunmay Yeung Andrew Briggs Funders: UK Department for International Development, LSHTM Health Economics and Financing Programme