WSC 2005 Final Abstracts

Implementation of a Discrete Event Simulator For Biological Self-Assembly Systems
Tiequan Zhang, Rori Rohlfs, and Russell Schwartz (Carnegie Mellon University)

Abstract:
We have implemented a simulation tool for the study of computationally challenging biological self-assembly systems, particularly viral protein shells. The simulator implements a generic model of self-assembly based on simple local binding interactions to specify the behavior of complex self-assembly reactions. Recently developed discrete event methods allow for fast quantitative simulation of these systems. The new simulator uses the Java language to implement the model in a portable, interactive graphical tool. The Java libraries can also be used directly to build customized simulations. This paper discusses the simulator model, the theoretical basis for its efficient operation, and implementation issues in its design. It also discusses empirical validation of the simulator package and presents sample applications.

Clinical Trial Factors in a Pain Transition State Model
Meyer Katzper (Food and Drug Administration)

Abstract:
This paper presents a pain state transition model which accounts for constraints used in clinical trials. The pain transition state model is an approach for summarizing, presenting and modeling pain state transitions in a population. Data used are from the ibuprofen arm of a number of clinical trials measuring dental extraction pain. The data de termine the state transition coefficients of the model. The pain process in the presence of an analgesic is thus fully characterized.

A Comparison of Screening Methods for Colorectal Cancer
Ali Tafazolli and Stephen D. Roberts (North Carolina State University) and Reid M. Ness and Robert S. Dittus (Vanderbilt University Medical Center)

Abstract:
We used a discrete-event simulation model of the natural history of Colorectal Cancer (CRC) to do a cost-effectiveness analysis comparing the latest CRC screening strategies recommended by the American Gastroenterological Association (AGA) and the newest screening modalities for which clinical efficacy has been established. Cost-effectiveness was based on discounted costs and quality-adjusted life-years. A probabilistic sensitivity analysis examined the uncertainty in important parameter estimates. Considering all populations (average and high risk), annual Fecal Occult Blood Test (FOBT), Sigmoidoscopy every five years and annual FOBT, and Colonoscopy every ten years were the three strategies that demonstrated a greater than 50% probability of not being dominated in probabilistic sensitivity analysis. Depending on the maximum acceptable marginal cost-effectiveness value, any of these procedures have a high likelihood of becoming preferred (most effective strategy given a specific cost limit per Quality-Adjusted Life-Year (QALY) saved).

Assessing the Viability of an Open Access Policy in an Outpatient Clinic: A DiscreteEvent and Continuous Simulation Modeling Approach
Ronald E. Giachetti, Edwin A. Centeno, Martha A. Centeno, and Ramakrishnan Sundaram (Florida International University)

Abstract:
This paper presents the preliminary results of an ongoing research project investigating the patient appointment scheduling for an outpatient clinic. The outpatient clinic was experiencing three problems of long patient throughput times, a large backlog of appointments, and a high no-show rate. We believe a new scheduling approach called Open Access could address all three problems. To analyze and make recommendations for improvement to patient cycle time we developed a discrete event simulation. To understand the factors leading to a high no-show rate we developed a systems dynamic simulation model. The study identified feasible strategies the clinic management could implement to greatly improve patient throughput time by 50%. Our preliminary results indicate that Open Access is a viable strategy for the clinic. Ongoing work is being conducted to refine the models and determine the best configuration of an Open Access scheduling policy for the outpatient clinic.

Evaluating Hospital Pharmacy Staffing and Work Scheduling Using Simulation
Charles W. Spry and Mark A. Lawley (Purdue University School of Industrial Engineering)

Abstract:
With increasing healthcare costs, an aging population, and a shortage of trained personnel it is becoming increasingly important for hospital pharmacy management to make good operational decisions. In the case of hospital inpatient pharmacies, making decisions about staffing and work scheduling is difficult due to the complexity of the systems used and the variation in the orders to be filled. In order to help BroMenn Healthcare make decisions about staffing and work scheduling a simulation model was created to analyze the impact of alternate work schedules. The model estimates the effect of changes to staffing and work scheduling on the amount of time medication orders take to process. The goal is to use the simulation to help BroMenn find the best schedule to get medications to the patients as quickly as possible by using pharmacy staff effectively.

Simulation Analysis of Appointment Scheduling in an Outpatient Department of Internal Medicine
Athula Wijewickrama and Soemon Takakuwa (Nagoya University)

Abstract:
Long waiting times for treatment in the outpatient department of internal medicine, followed by short consultations has long been a complaint of patients. This issue is becoming increasingly important in Japan with the progressively aging society. In this context, a discrete event simulation model to examine various appointment schedules in a mixed-patient type environment in an outpatient department of a general hospital was developed. A special purpose data generator was designed to validate the model and to conduct experiments in bottleneck situations at consultation rooms in the existing system. Some efficient appointment schedules (ASs) were identified, which drastically reduced patient waiting time while keeping doctor idle time as low as possible without adding extra resources. The sensitivity of performance was examined under three realistic environmental factors: no show, variance of consultation time, and variation of walk-ins.