OBJECTIVES: To validate the Treatment Transitions Model (TTM) using real-world data   METHODS: Patients with at least one medical claim for type 2 diabetes mellitus (T2DM) and one pharmacy claim for a non-insulin antidiabetic medication during the index period (January 2008 - August 2013) were identified from a large health plan claims database. The first claim for T2DM was set as the index date. Patients enrolled a year prior to the index date, and at least two years post-index, were included in this study. Based on treatment guidelines recommended by American Diabetes Association and European Association for the Study of Diabetes, four treatment escalation pathways were chosen. Baseline population characteristics including demographics and complication history were collected from the database retrospectively. These characteristics and trial-based treatment efficacies were used by the TTM to predict the incidence of diabetes-related complications during the post-index period, which was then compared to the incidence in claims data.   RESULTS: Only one pathway – patients starting on one oral antidiabetic medication and escalating to three oral antidiabetic medications had a sufficient base sample size (n=296) to include in the analysis. Comparing the 2-year prevalence of diabetes-related complications predicted by TTM to those observed in the claims database revealed (respectively): retinopathy (11.5% vs. 18.9%), microalbuminuria (5.6% vs. 21.6%), peripheral neuropathy (33.4% vs. 38.5%), angina (20.0% vs. 36.8%), and stroke (13.8% vs. 19.3%).   CONCLUSIONS: A key finding was that the treatment pathways recommended by the guidelines were not observed in real-world settings. The higher prevalence of complications in claims data than what was predicted by the model may indicate issues in interpreting diagnosis codes, or underlying issues in the population not originally observed in the baseline characteristics. Work is ongoing to refine the model and investigate gaps between real-world data and model predictions.