Julie S. Ivy

Assessing Dynamic Breast Cancer Screening Policies

Questions regarding the relative value and frequency of mammography screening for premenopausal women versus postmenopausal women remain open due to the conflicting age-based dynamics of both the disease (increasing incidence, decreasing aggression) and the accuracy of the test results (increasing sensitivity and specificity). To investigate these questions, we formulate a partially observed Markov chain model that captures several of these age-based dynamics not previously considered simultaneously. Using sample-path enumeration, we evaluate a broad range of policies to generate the set of “efficient” policies, as measured by a lifetime breast cancer mortality risk metric and an expected mammogram count, from which a patient may select a policy based on individual circumstance. We demonstrate robustness with respect to small changes in the input data and conclude that, in general, to efficiently achieve a lifetime risk comparable to the current risk among U.S. women, screening should start relatively early in life and continue relatively late in life regardless of the screening interval(s) adopted. The frontier also exhibits interesting patterns with respect to policy type, where policy type is defined by the relationship between the screening interval prescribed in younger years and that prescribed later in life.

A simulation-based approach for inventory modeling of perishable pharmaceuticals

Pharmaceutical expenditures are increasing for hospital systems nationwide. We model the inventory and ordering policies for perishable drugs in the setting of an inpatient hospital pharmacy. We consider two stages of inventory: raw material and finished good (e.g. intravenous). We use a two-phased approach to explore policy structures that could be implemented in the hospital pharmacy. We develop a policy which is based on the idea that hospitals can improve both costs and patient demand fulfillment by using knowledge of patient mix to guide their drug inventory and preparation decisions. We compare this policy to a simpler stationary base stock policy. The policies are evaluated on the basis of (1) shortage cost, (2) outdating cost (expirations), and (3) holding cost through a range of cost scenarios.

Pelvic Floor Consequences of Cesarean Delivery on Maternal Request in Women with a Single Birth: A Cost-effectiveness Analysis

BACKGROUND The potential benefit in preventing pelvic floor disorders (PFDs) is a frequently cited reason for requesting or performing cesarean delivery on maternal request (CDMR). However, for primigravid women without medical/obstetric indications, the lifetime cost-effectiveness of CDMR remains unknown, particularly with regard to lifelong pelvic floor consequences. Our objective was to assess the cost-effectiveness of CDMR in comparison to trial of labor (TOL) for primigravid women without medical/obstetric indications with a single childbirth over their lifetime, while explicitly accounting for the management of PFD throughout the lifetime. METHODS We used Monte Carlo simulation of a decision model containing 249 chance events and 101 parameters depicting lifelong maternal and neonatal outcomes in the following domains: actual mode of delivery, emergency hysterectomy, transient maternal morbidity and mortality, perinatal morbidity and mortality, and the lifelong management of PFDs. Parameter estimates were obtained from published literature. The analysis was conducted from a societal perspective. All costs and quality-adjusted life-years (QALYs) were discounted to the present value at childbirth. RESULTS The estimated mean cost and QALYs were

Univariate input models for stochastic simulation

14,259 (95% confidence interval [CI]

Optimal two-phase vaccine allocation to geographically different regions under uncertainty

8,964-

Combined DES/SD model of breast cancer screening for older women, II: screening-and-treatment simulation

24,002) and 58.21 (95% CI 57.43-58.67) for CDMR and

Patient-based pharmaceutical inventory management: a two-stage inventory and production model for perishable products with Markovian demand

13,283 (95% CI

Managing Supply Critical to Patient Care: An Introduction to Hospital Inventory Management for Pharmaceuticals

7,861-

Cost-effectiveness analysis of vaccination and self-isolation in case of H1N1

23,829) and 57.87 (95% CI 56.97-58.46) for TOL over the combined lifetime of the mother and the child. Parameters related to PFDs play an important role in determining cost and quality of life. CONCLUSIONS When a woman without medical/obstetric indications has only one childbirth in her lifetime, cost-effectiveness analysis does not reveal a clearly preferable mode of delivery.

Modeling for the equitable and effective distribution of food donations under stochastic receiving capacities

Techniques are presented for modelling and then randomly sampling many of the continuous univariate probabilistic input processes that drive discrete-event simulation experiments. Emphasis is given to the generalized beta distribution family, the Johnson translation system of distributions, and the Bézier distribution family because of the flexibility of these families to model a wide range of distributional shapes that arise in practical applications. Methods are described for rapidly fitting these distributions to data or to subjective information (expert opinion) and for randomly sampling from the fitted distributions. Also discussed are applications ranging from pharmaceutical manufacturing and medical decision analysis to smart-materials research and health-care systems analysis.