Switching from Multiple Daily Injections to CSII Pump Therapy: Insulin Expenditures in Type 2 Diabetes

Objectives To identify variations in expenditures and utilization of insulin and other antidiabetes medications by comparing patients with type 2 diabetes mellitus using continuous subcutaneous insulin infusion (CSII) pump therapy versus multiple daily injection (MDI) therapy. Study Design Truven Health Analytics MarketScan Commercial Claims and Encounters Database and Medicare Supplemental Database for 2006 to 2010 were used in a difference-in-differences approach that took advantage of variation in the timing of the switch from MDI therapy to CSII pump therapy. Methods Continuous users of MDI therapy throughout the study period were compared with those who switched to the CSII pump therapy during this period. Specifications included: coefficient estimates from cross-sectional ordinary least squares (OLS) regressions with: 1) no additional controls, 2) controls for patient demographics and comorbidities, and 3) patient fixed effects. Propensity score matching at baseline mitigated concerns regarding patient selection bias. Results While insulin expenditures rose during the study period, switching to CSII pump therapy led to sizable reductions in insulin expenditures. This reduction in insulin expenditures due to switching varied between $657 (standard error [SE] $126; P <. 01) and $1011 (SE $250.60; P <. 01) per year. Conclusions This study demonstrated a significant reduction in insulin expenditures among MDI patients who switched to CSII pump therapy at various times throughout the study period.