Development and Validation for a Model of Treatment of Glaucoma for the United States

Evaluation of cost-effectiveness for chronic disease treatment requires development and validation of a model of disease progression. In this presentation we describe the development of a decision analytic model and how the model might be used to enhance evaluation of the cost-effectiveness of glaucoma treatment in the US. We constructed a Markov model using patient-level data from three large studies of glaucoma treatment and evaluated the validity of the model. Glaucoma severity and disease progression were defined clinically in terms of visual field loss expressed as mean deviation (MD) measured in decibels (dB). We used patient level data for the model came from the Collaborative Initial Glaucoma Treatment Study (CIGTS n=574), the Ocular Hypertension Treatment Study (OHTS n=1,546), and the Advanced Glaucoma Intervention Study (AGIS n=580). The model was estimated with TreeAge software using a microsimulation approach. For validation, a clinically significant difference was considered to be 3 decibels (dB) of MD. Three variables---age, race, and starting MD---were most strongly associated with change in MD. Predicted values from the model were regressed on actual study results. The R2 for the right eye was 0.72, and for the left 0.70. Our initial results indicate that the glaucoma progression model properly predicts the result of disease progression in over 80% of “participants”. This suggests that our modeling approach provides a reasonable reflection of real world progression and provides a useful tool for researchers and policy makers. We conclude by discussing the impact of precise assessment of progression on reporting cost-effectiveness.