Economic evaluations relating to diabetes: a descriptive review and their compliance with guidance.

From a search of the Health Economics Evaluations Database (HEED), 301 studies relating to diabetes-related interventions were identified. Of these, 223 studies contained some original data, i.e., were applied studies. Over the 1990s, the number of studies undertaken in this area appears to be increasing year on year, and more of the studies are applicable to the USA than to all other countries combined. Most studies are peer reviewed, the main type of analysis is cost-consequence, and the interventions most often assessed are pharmaceutical and care services. Both the public and the private sectors sponsor many of these studies. However, only a fraction of these studies appear to accord with guidance for good economic evaluation. For example, when the search criteria were tightened to capture only those studies that consider both outcomes and costs, 173 studies were identified. Narrowing the search criteria to capture only those studies that were based on randomized controlled trial (RCT) or modeling data-the methods recommended by the US Panel and the National Institute of Clinical Excellence (NICE)-reduced the sample to 56 studies. With specific focus on those studies that evaluated pharmaceuticals, only the modeling approach appeared to show any compliance at all with another key recommendation of the existing guidance on methods; that of using outcome measures that are applicable to a long-term time horizon. Though modeling does offer certain advantages over RCTs (for example, a larger range of comparators can be more readily incorporated, long-term outcome measures can be more easily and inexpensively estimated), modeling results have less internal validity. Also, modeling in itself relies on good RCT data. Therefore, the results of economic evaluations should be interpreted with care, irrespective of whether they are principally based on RCT or model-based methods.