OBJECTIVES: A published CEA of the 10 year DPP/DPPOS study, comparing placebo (PBO), metformin (MET), individual and group lifestyle (ILS and GLS) interventions concluded, confusingly, that metformin and lifestyle interventions were cost-effective. We clarify and extend the original work to address decision uncertainty through probabilistic sensitivity analysis (PSA).

METHODS: METHODS: Various costs and effectiveness (QALYs – quality-adjusted life years) numbers from the original publication (including making a correction to the QALY calculation) were used to calculate incremental cost-effectiveness ratios (ICERs). We clarified the significant ambiguity of the original paper’s conclusions using the cost-effectiveness plane. We used PSA to construct cost-effectiveness acceptability curves and frontiers (CEAC/Fs).

RESULTS: Analysis of both the original data and of results with the corrected QALY calculation clearly indicated that, relative to the other intervention, GLS dominates or, for likely WTP thresholds, is the cost-effective intervention. If GLS is eliminated as an option, ILS is optimal, as it is the most effective intervention and has an acceptable ICER ($19,433). Metformin is cost-effective only if the WTP threshold is unrealistically low (<$1,585/QALY). The PSA and CEAC/Fs analyses show that the GLS probability of being cost-effective varies, but has the highest probability of being CE throughout (and far beyond) a wide range of “reasonable” WTP thresholds. The only other alternative with a significant probability of being cost effective is ILS.

CONCLUSIONS: The original paper's ambiguous/conflicting conclusions (e.g., “policies should support the funding of intensive lifestyle and metformin interventions”) misrepresented and obscured the simplicity of the results. The value of various depictions of deterministic and probabilistic results was shown by clarifying the original results – if these data reflect the performance of the interventions accurately, GLS (or ILS if GLS not available) was the cost-effective alternative in diabetes prevention. Contrary to the original article, there was no place for metformin in diabetes prevention.