Cost effectiveness of insulin glargine plus oral antidiabetes drugs compared with premixed insulin alone in patients with type 2 diabetes mellitus in Canada

Several treatment options are available for patients with type 2 diabetes mellitus who are making the transition from oral antidiabetes drugs (OADs) to insulin. Two options currently recommended by the Canadian Diabetes Association for initiating insulin therapy in patients with type 2 diabetes who are no longer responsive to OADs alone are insulin glargine plus OADs, and premixed insulin therapy only. Because of differences in efficacy, adverse events (such as hypoglycaemia) and acquisition costs, these two treatment options may lead to different long-term clinical and economic outcomes.

To determine the cost effectiveness of insulin glargine plus OADs compared with premixed insulin without OADs in insulin-naive patients with type 2 diabetes in Canada.

Using treatment effects taken from a published clinical trial, the validated IMS-CORE Diabetes Model was used to simulate the long-term cost effectiveness of insulin glargine with OADs, versus premixed insulin. Input treatment effects for the two therapeutic approaches were based on changes in glycosylated haemoglobin A_1c (HbA_1c) at clinical trial endpoint, and hypoglycaemia rates. The analysis was conducted from the perspective of the Canadian Provincial payer. Direct treatment and complication costs were obtained from published sources (primarily from Ontario) and reported in $Can, year 2008 values. All base-case costs and outcomes were discounted at 5% per year. Sensitivity analyses were conducted around key parameters and assumptions used in the study. Outcomes included direct medical costs associated with both treatment and diabetes-related complications. Cost-effectiveness outcomes included total average lifetime (35 years) costs, life expectancy (LE), QALYs and incremental cost-effectiveness ratios (ICERs).

Base-case analyses showed that, compared with premixed insulin only, insulin glargine in combination with OADs was associated with a 0.051-year increase in LE and a 0.043 increase in QALYs. Insulin glargine plus OADs showed a very slight increase in total direct costs ($Can343 ± 2572), resulting in ICERs of $Can6750 per life-year gained (LYG) and $Can7923 per QALY gained. However, considerable uncertainty around the ICERs was demonstrated by insulin glargine having a 50% probability of being cost effective at a willingness-to-pay threshold of $Can10 000 per QALY, and a 54% probability at a $Can20 000 threshold. Base-case results were most sensitive to assumed disutilities for hypoglycaemic events, to the assumed effect of insulin glargine plus OADs on HbA_1c, and to its assumed acquisition costs.

These findings should be interpreted within the context of a large degree of uncertainty and of several study limitations that include a single clinical trial as the source for primary treatment assumptions and a single province as the source for most cost inputs. Under current study assumptions and limitations, insulin glargine plus OADs was projected to be a cost-effective option, compared with premixed insulin only, for the treatment of insulin-naive patients with type 2 diabetes unresponsive to OADs. Additional work is needed to examine the generalizability of the findings to individual jurisdictions of the Canadian healthcare system.