Over 10 years, lifestyle intervention and metformin were cost-effective or cost saving compared with placebo.
Previously, we reported the clinical and economic outcomes of an intent-to-treat analysis of the combined 10 years of the Diabetes Prevention Program/Diabetes Prevention Program Outcomes Study (DPP/DPPOS).1,2 In that analysis, participants were analyzed according to their randomized treatment group whether or not they adhered to their assigned treatment. In this paper, we report the results of an “on treatment” or “per protocol” analysis of DPP/ DPPOS. We assess outcomes by treatment group for participants who were adherent to their randomized assignments and compare the effectiveness and cost utility of the intensive lifestyle intervention (lifestyle) and the metformin intervention (metformin) with the placebo intervention (placebo).
Our previously published 10-year intent-to-treat analysis of DPP/ DPPOS used data from all randomized participants including those who did not adhere to their randomized treatments, and so likely underestimated both the effectiveness and the benefits of lifestyle and metformin. In real-world clinical practice, neither costs nor benefits are incurred by nonparticipants, but among participants, both intervention costs and benefits are likely to be greater. Our goal in this analysis of the DPP/ DPPOS is to extend our previous analyses to estimate the clinical effectiveness and cost-effectiveness of diabetes prevention among metformin participants who remained on treatment with metformin and lifestyle participants who succeeded in losing weight.
The DPP enrolled 3234 participants with impaired glucose tolerance and fasting hyperglycemia who were at least 25 years of age and had body mass index of 24 kg/m2 or higher (22 kg/m2 in Asian Americans).3 The protocol and informed consent procedures were approved by all responsible institutional review boards. Participants signed written consent forms after discussion of all aspects of the study with study staff. For this analysis, we assigned costs related to finding the participants randomized to lifestyle and metformin but not the participants randomized to placebo. In estimating the costs of finding participants, we assumed that 10.4% of adults aged 45 to 74 years would be eligible to participate.4 We further assumed that potentially eligible subjects would be tested with a random capillary glucose level.5 If the capillary glucose level was >110 mg/dl, an oral glucose tolerance test (OGTT) would be performed6 and those with abnormal OGTTs would have a 15-minute visit with a physician to discuss the results. Based on the sensitivity, specificity, and reproducibility of the tests, we estimated that 12.8% of subjects screened would be eligible to participate in the DPP and that the average cost per eligible participant identified would be $173.
Click here to read the full-text version of this article, which was originally published in The American Journal of Managed Care.