Our systematic review showed that, with few exceptions, ADA-recommended interventions for preventing or treating diabetes and its complications were cost saving, very cost-effective, or cost-effective (i.e., with an ICER of less than $50,000 per QALY or LYG), although the strength of evidence varied. Generally, interventions that cost less than $50,000 per QALY are considered an efficient use of resources and worth recommending (11
). Interventions with strong evidence for being cost saving, very cost-effective, or cost-effective should be considered for implementation. Interventions with supportive evidence for being cost saving, very cost-effective, or cost-effective should be adopted if extra resources are available or if similar interventions with strong evidence are unavailable or infeasible in a specific setting.
The one intervention recommended by the ADA that was shown as not CE was screening for type 2 diabetes of all U.S. residents aged 45 years and older. When considering allocating resources efficiently, universal screening for undiagnosed diabetes should be undertaken with great caution. The high CE ratio for universal screening for undiagnosed type 2 diabetes was primarily attributable to the small gain in health benefit. For example, screening everyone aged 45 years and older gained only 0.003 QALY per eligible person compared with no screening. However the additional costs associated with screening and early treatments were relatively large ($564 per person). Although detecting and treating diabetes earlier can prevent future diabetes-related complications and their associated medical costs, such savings are relatively small ($57 per person). Combining the health benefit and costs would yield an ICER of more than $1 million per QALY (35
). An alternative to broad screening is to focus on screening persons with additional risk factors, such as hypertension. Such targeted screening is shown to be cost-effective when compared with no screening or universal screening.
Intensive glycemic control for all U.S. residents with type 2 diabetes diagnosed at age 25 years and older is marginally CE. However the cost-effectiveness of this intervention varies by age at the time of the diabetes diagnosis. The intervention is cost-effective in persons diagnosed at 25–54 years of age. However, intensive glycemic control for those diagnosed with diabetes at 55 years of age and older is not cost-effective. In fact, this result is consistent with the ADA's recommendation of less stringent A1C goals for patients with limited life expectancies.
The ADA recommended annual eye screening for diabetic retinopathy. This recommended intervention is very cost-effective compared with no screening in persons with type 2 diabetes. If considering the efficient allocation of resources, however, screening every other year might be a better alternative. Screening annually leads to a small health benefit but results in a moderate additional cost. For example, Vijan et al. (69
) showed that, compared with a 2-year screening, annual screening among persons at moderate risk (65 years old with A1C level 9%) resulted in an increase of 2–3 days of sight at a cost of $540–690 per person. However the ADA also stated in its recommendation that “less frequent exams (every 2–3 years) may be considered following one or more normal eye exams.”
For the interventions with uncertain CE (including optimal age of starting screening for type 2 diabetes), following the current treatment guidelines may be the best option until more evidence on their CE is available.
The CEs of 43 ADA-recommended interventions were evaluated. Of these, 25 were in the “strong” evidence category. This number would probably have been larger if we had used less stringent criteria to define evidence as being strong. For example, evidence on the CE of using metformin to prevent type 2 diabetes among high-risk individuals was considered “supportive” in our current classification even though the efficacy of the intervention was shown by well-conducted multi-center large clinical trials in different country settings (71
), and its CE was evaluated by “excellent” CE studies (25
). This intervention was considered to have supportive evidence because it ranked lower in the ADA recommendations (7
Among all the interventions considered, evidence for the CE of primary prevention through intensive lifestyle modification was the strongest regarding the quantity and quality of the CE studies and efficacy data. Several well-conducted clinical trials have shown the efficacy of intensive lifestyle modification in preventing diabetes in different country settings, such as the U.S. DPP (71
), Finnish Diabetes Prevention Study (73
), China Da Qing Diabetes Prevention Study (74
), and Indian DPP (72
). Eight cost-effectiveness studies (seven of them rated as excellent quality) have been conducted by different groups in different countries based on data from these well-conducted clinical trials (15
). The results from these studies consistently showed that intensive lifestyle modification in persons with impaired glucose tolerance was cost saving or very cost-effective in the long run (15
). Even in a short-term and one-on-one consulting setting, the intervention remained cost-effective (66
). The intervention would be more cost-effective than existing studies show if the cost of the lifestyle intervention could be reduced. This might be achieved by changing the setting in which the intervention is provided. Only one study found a DPP-like intervention to be marginally cost-effective (25
). Even in this study, however, the intervention would have been very cost-effective (23
) if done in the type of group environment that is most likely in a real-world setting. A group-based, DPP-style lifestyle intervention partnership with the YMCA costs $275 to $325 per participant in the first year compared with $1,400 in the one-on-one setting of the DPP trial (75
). Preventing diabetes, in particular by lifestyle modification, is not only effective but also a very efficient use of health care resources.
The CE of an intervention can vary by country setting. For example, intensive glycemic control (with a goal A1C level of 7%) in type 2 diabetic patients diagnosed at 25 years of age and older was marginally cost-effective in the U.S. but very cost-effective in other developed countries. Although the efficacy data of all studies of intensive glycemic control in type 2 diabetic patients were based on the same UKPDS data, the cost data were based on how residents of the different countries used health services and the cost of those services. The incremental cost of intensive glycemic control was much higher in the U.S. than in the U.K. because of different practice patterns. Patients outside the U.S. did not receive diabetes disease management services and had less frequent self-testing and physician office visits than their U.S. counterparts at the time these studies were conducted. If using the health services as described in the UKPDS setting but with the U.S. cost of these services, the CE of the intensive glycemic control in the U.S. would resemble that of other developed countries.
Future economic evaluation of diabetes interventions should consider the following. First, more studies are needed to evaluate the CE of interventions that fell in the “supportive” evidence category. For studies with weaker efficacy data, further efficacy studies are needed. Second, there are also 38 interventions recommended by the ADA but they have not been evaluated for their CE or the studies did not meet the inclusion criteria for our review (list is available upon request from the authors). The CE of these interventions should be assessed. Third, more CE studies are needed that address interventions in real-world settings. For example, few studies considered attrition rate, noncompliance, and dropout rates in evaluating CE. Fourth, more studies are needed to evaluate the CE of public policy changes. Only two studies evaluated public insurance reimbursement of ACEI therapy and both found this intervention to be cost saving. Finally, the CE of multiple interventions needs to be evaluated. In most real-world settings, patients receive multiple interventions simultaneously. Nearly all previous studies only evaluated the CE of a single intervention.
This review's conclusions should be used with caution. First, our conclusions are based on available information up to May 2008. More studies have been published since then. In addition, data on both the effectiveness and cost of an intervention could have changed since the time the original study was conducted. Using the newly available data could change our current conclusion. For example, in our review, we concluded that the CE of optimal age to start screening for type 2 diabetes was uncertain. A recently published CE study on age at initiation of screening for type 2 diabetes, released after our analysis was complete, might change that conclusion (76
). Another example is the large decrease in costs for metformin, statins, and ACEIs. Studies that evaluate CE using current costs might look more favorably on interventions that include statins and ACEIs than those reported here. Reevaluating the costs and benefits of these interventions, using current-day costs, is beyond the scope of this study. Second, when using the results and conclusions of our review, readers need to be certain that terms are understood correctly. For example, “intensive insulin treatment” in our review meant “multiple insulin injection” or “insulin infusion.” Developments in medical technology might make continuous glucose monitoring systems, which record blood glucose levels throughout the day and night, more common. Drugs such as TZD Byetta and Gliptin, not available at the time covered by this review, are increasingly used to achieve intensive glycemic control. The CE of treatment with these and other new devices and drugs are unknown. New CE analyses are needed for these new interventions. Third, not everyone will necessarily agree with our classification criteria. Different classification criteria might have changed some conclusions. Fourth, most of the CE studies are based on simulation modeling. Although good-quality simulation modeling can provide information at a much lower cost than clinical trials, models are based on assumptions and represent a simplification of—and therefore might depart from—reality. Fifth, these CE studies use different methods, which could account for some differences in CERs. If the results from different models were consistent, we would have more confidence in the conclusion on the CE of the intervention. Sixth, we used the same threshold for the classification of the CE of interventions regardless of whether the ICERs were expressed as dollars per LYG or dollars per QALY, although they are different measures. The studies that reported costs per LYG did not incorporate the impact of the intervention on quality of life into the analysis. If they did, the cost per QALY could be higher, lower, or the same depending on the relative magnitude of the health benefit of the intervention on quality of life. Seventh, the interpretation of the CE of an intervention must include consideration of variables such as study population, comparison interventions, and country setting. Lastly, our recommendations are based on the CE of the interventions and not their efficacy; therefore, these recommendations are not necessarily the same as the ADA recommendations.
The importance of CE in decision making should not be overstated. CE is only one aspect to consider. CE analysis does not address the distribution of costs and the benefits of an intervention, societal or personal willingness to pay, social and legal aspects, or ethical issues associated with each intervention. All these aspects are important in formulating public policy. The good news is that our study shows that a majority of the recommended diabetes interventions provide both health benefits and good use of health care resources.