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The Singapore Diabetes Prevention Program Cost-Effectiveness Analysis Revisited: Proper Methods Overturn Previous Conclusions

Speaker(s)

Paredes J1, Rittenhouse B2
1MCPHS University, Beverly, MA, USA, 2MCPHS University, Winchester, MA, USA

Presentation Documents

OBJECTIVES: A 2014 Singapore Cost-Effectiveness Analysis (CEA) from a healthcare system perspective claimed that Metformin and Lifestyle modification treatments were cost-effective for patients classified as having Pre-Diabetes. However, Incremental Cost-Effectiveness Ratios (ICERs) were calculated incorrectly, comparing all treatment alternatives to a common (Placebo) alternative. Our main objective is to reproduce, correct and extend that analysis, using correct ICER calculation methods and to indicate the extent of losses when incorrectly implementing treatments that are not cost-effective.

METHODS: We reproduced original costs, effects and (incorrectly calculated) ICERs in the original analysis. ICERs were then calculated correctly, using textbook methods. The analysis was also expanded, using Net Loss Curves, showing the extent of losses in implementing any but the optimal treatment.

RESULTS: When rerunning the Singapore model, the reproduction of the cost and QALY numbers showed that results were consistent with the original work. However, the only ICER relevant to report is Lifestyle vs. Placebo ($18,778 per QALY); the Metformin alternative is extendedly dominated by the combination of Lifestyle and Placebo. The expected net loss from implementing Metformin over the optimal Lifestyle is $1,036 per patient at a WTP value of $50,000. This may be scaled up to a population level by multiplying that by the number of discounted total pre-diabetes patients over time who could be influenced by such a decision.

CONCLUSIONS: The Singapore DPP CEA main conclusions were that both the Lifestyle and Metformin interventions were cost-effective. We demonstrated that this claim of dual cost-effective treatments was incorrect, under the healthcare system perspective. This incorrect conclusion resulted from an inappropriate comparison of all alternatives to a common Placebo alternative. The expected Net Loss Curves demonstrated the high costs of investing in an alternative that is not cost-effective.

Code

EE453

Topic

Economic Evaluation, Study Approaches

Topic Subcategory

Cost-comparison, Effectiveness, Utility, Benefit Analysis, Decision Modeling & Simulation, Value of Information

Disease

Diabetes/Endocrine/Metabolic Disorders