Sensitivity of diabetic retinopathy associated vision loss to screening interval in an agent-based/discrete event simulation model.

OBJECTIVE: To examine the effect of changes to screening interval on the incidence of vision loss in a simulated cohort of Veterans with diabetic retinopathy (DR). This simulation allows us to examine potential interventions without putting patients at risk. METHODS: Simulated randomized controlled trial. We develop a hybrid agent-based/discrete event simulation which incorporates a population of simulated Veterans--using abstracted data from a retrospective cohort of real-world diabetic Veterans--with a discrete event simulation (DES) eye clinic at which it seeks treatment for DR. We compare vision loss under varying screening policies, in a simulated population of 5000 Veterans over 50 independent ten-year simulation runs for each group. RESULTS: Diabetic Retinopathy associated vision loss increased as the screening interval was extended from one to five years (p<0.0001). This increase was concentrated in the third year of the screening interval (p<0.01). There was no increase in vision loss associated with increasing the screening interval from one year to two years (p=0.98). CONCLUSIONS: Increasing the screening interval for diabetic patients who have not yet developed diabetic retinopathy from 1 to 2 years appears safe, while increasing the interval to 3 years heightens risk for vision loss.

An Agent-Based Modeling Template for a Cohort of Veterans with Diabetic Retinopathy.

BACKGROUND: Agent-based models are valuable for examining systems where large numbers of discrete individuals interact with each other, or with some environment. Diabetic Veterans seeking eye care at a Veterans Administration hospital represent one such cohort. OBJECTIVE: The objective of this study was to develop an agent-based template to be used as a model for a patient with diabetic retinopathy (DR). This template may be replicated arbitrarily many times in order to generate a large cohort which is representative of a real-world population, upon which in-silico experimentation may be conducted. METHODS: Agent-based template development was performed in java-based computer simulation suite AnyLogic Professional 6.6. The model was informed by medical data abstracted from 535 patient records representing a retrospective cohort of current patients of the VA St. Louis Healthcare System Eye clinic. Logistic regression was performed to determine the predictors associated with advancing stages of DR. Predicted probabilities obtained from logistic regression were used to generate the stage of DR in the simulated cohort. RESULTS: The simulated cohort of DR patients exhibited no significant deviation from the test population of real-world patients in proportion of stage of DR, duration of diabetes mellitus (DM), or the other abstracted predictors. Simulated patients after 10 years were significantly more likely to exhibit proliferative DR (P<0.001). CONCLUSIONS: Agent-based modeling is an emerging platform, capable of simulating large cohorts of individuals based on manageable data abstraction efforts. The modeling method described may be useful in simulating many different conditions where course of disease is described in categorical stages.

Enhancing entrance into PTSD treatment for post-deployment veterans through collaborative/integrative care.

High rates of posttraumatic stress disorder (PTSD) among post-deployment veterans and the associated long-term consequences highlight the importance of early identification and treatment. The Veterans Health Administration (VHA)'s Primary Care Mental Health Integration (PCMHI) program aims to increase identification and access to care for veterans with mental illness, decrease stigma, improve continuity of care, and the efficiency of healthcare utilization. This project examines PCMHI's progress towards these goals within the Operation Iraqi Freedom/Operation Enduring Freedom (OEF/OIF) population. We examined data from consults to the OEF/OIF PTSD clinic for 18 months. PCMHI placed 129 consults and 91 (70.5%) were completed. Veterans referred by PCMHI tended to have increased consult completion in specialty care, higher rates of confirmed PTSD, however, no significant differences in reported PTSD symptoms, or follow-up visits in the OEF/OIF PTSD clinic compared to Veterans referred from the hospital at large. PCMHI potentially preserve resources, increases continuity of care, and increases treatment access for OEF/OIF/OND veterans.