Cost effectiveness models are widely used to help policy makers and clinicians make decisions about alternative interventions. Models have limitations that are well understood—a model is only as reliable, or generalisable, as the assumptions and data that inform it. Moreover, a cost effectiveness model will not deal with questions about feasibility, acceptability, or affordability that may be crucial to decisions about implementation. However, decision analysis models often help to clarify the key factors likely to influence cost effectiveness, so that decision makers can better understand the importance of remaining uncertainties and make more logical decisions in the face of uncertainty.1 2

In the accompanying paper, Gillies and colleagues report a cost effectiveness analysis for screening and prevention of type 2 diabetes.3 They compare four strategies—screening for diabetes; screening for diabetes and impaired glucose tolerance, followed by either lifestyle interventions or drugs; and no screening. Their findings are consistent with …