Biomedical subjects

Mark S Roberts

Publications and source records attributed to Mark S Roberts.

41 records · Page 3Linked to original sources

PubMedDate not supplied

Willingness to pay for a quality-adjusted life year: implications for societal health care resource allocation.

BACKGROUND: Health-state preferences can be combined with willingness-to-pay (WTP) data to calculate WTP per quality-adjusted life year (QALY). The WTP/QALY ratios provide insight into societal valuations of expenditures for medical interventions. METHODS: The authors measured preferences for current health in 3 patient populations (N = 391) using standard gamble, time trade-off, visual analog scale, and WTP, then they calculated WTP/QALY ratios. The ratios were compared with several proposed cost/QALY cost-effectiveness ratio thresholds, the value-of-life literature, and with WTP/QALY ratios derived from published preference research. RESULTS: Mean WTP/QALY ratios ranged from 12,500 to 32,200 US dollars (2003 US dollars). All values were below most published cost-effectiveness ratio thresholds, below the ratio from a prototypic medical treatment covered by Medicare (i.e., renal dialysis), and below ratios from the value-of-life literature. The WTP/QALY ratios were similar to those calculated from published preference data for patients with symptomatic meno-pause, dentofacial deformities, asthma, or dermatologic disorders. CONCLUSIONS: WTP/QALY ratios calculated using preference data collected from diverse populations are lower than most proposed thresholds for determining what is "cost-effective." Current proposed cost-effectiveness ratio thresholds may overestimate the willingness of society to pay for medical interventions.

Adult↗

PubMedDate not supplied

Incorporating biological natural history in simulation models: empirical estimates of the progression of end-stage liver disease.

OBJECTIVE: To develop an empiric natural-history model that can predict quantitative changes in the laboratory values and clinical characteristics of patients with end-stage liver disease (ESLD), to be used to calibrate an individual microsimulation model. METHODS: The authors report the development of a stochastic model that uses cubic splines to interpolate between observed laboratory values over time in a cohort of 1997 patients with ESLD awaiting liver transplantation at the University of Pittsburgh Medical Center. The splines were recursively sampled to provide a stochastic, quantitative natural history of each candidate's disease. RESULTS: The model was able to simulate the types of erratic disease trajectories that occur in individual patients and was able to preserve the statistical properties of the natural history of ESLD in cohorts of real patients. Moreover, the model was able to predict pretransplant survival rates (87% at 1 year), which were statistically similar to rates observed in the authors' local cohort (92%). CONCLUSIONS: Cubic splines can be used to generate quantitative natural histories for individual patients with ESLD and may be useful for developing clinically robust microsimulation models of other diseases.

Disease Progression↗

PubMedDate not supplied

The cost-effectiveness of strategies to reduce mortality from an intentional release of aerosolized anthrax spores.

BACKGROUND: Intentional exposures to aerosolized Bacillus anthracis spores have caused fatalities. OBJECTIVE: To evaluate the cost-effectiveness of strategies to reduce mortality from future inhalational anthrax exposures. METHODS: Computer cohort simulation of a 100,000-person single-site exposure (worst-case scenario) and a 100-person multiple-site exposure (resembling the recent US attack). For each scenario, universal vaccination and an emergency surveillance and response (ESR) system were compared with a default strategy that assumed eventual discovery of the exposure. RESULTS: If an exposure was unlikely to occur or was small in scale, neither vaccination nor an ESR system was cost-effective. If an exposure was certain and large in scale, an ESR system was more cost-effective than vaccination ($73 v. $29,600 per life-year saved), and a rapid response saved more lives than improved surveillance. CONCLUSIONS: Strategies to reduce deaths from anthrax attacks are cost-effective only if large exposures are certain. A faster response is more beneficial than enhanced surveillance.

Aerosol Propellants↗

PubMedDate not supplied

Increasing the efficiency of Monte Carlo cohort simulations with variance reduction techniques.

The authors discuss techniques for Monte Carlo (MC) cohort simulations that reduce the number of simulation replications required to achieve a given degree of precision for various output measures. Known as variance reduction techniques, they are often used in industrial engineering and operations research models, but they are seldom used in medical models. However, most MC cohort simulations are well suited to the implementation of these techniques. The authors discuss the cost of implementation versus the benefit of reduced replications.

Computer Simulation↗

PubMedDate not supplied

Teaching medical decision modeling: a qualitative description of student errors and curriculum responses.

BACKGROUND: Novice medical decision modelers are prone to errors. The purpose of this article is to describe the common errors committed by decision modeling students and the changes made to a structured decision modeling project course in response. CURRICULUM: The decision modeling curriculum includes month-long segments in decision analysis, cost-effectiveness analyses, and a project course. In the project course, students solve a decision problem with prespecified assumptions and input variable values, with the expectation that all reach the same answer. At first, students worked in groups of 2 or 3 but more recently work individually; over time, there have been other changes in the course. Originally, the only assignment was an abstract and 10-minute presentation describing their solution, but now periodic homework monitors progress. OUTCOMES: Students' results frequently differed significantly from the expected answers. Errors were common in sensitivity analyses and model construction, among other areas. Defensible differences in structural programming decisions were rare. More recently, result ranges have narrowed as stepwise homework ensures progress and areas prone to error are emphasized. Student communication is timelier, facilitated by homework-related questions. Individual, rather than group, work avoids potential problems with weaker students being carried by the more advanced. Student satisfaction has increased, with more beginning their own projects afterward. CONCLUSION: Solving a common decision problem is an efficient teaching tool. Closer supervision leads to increased satisfaction and decreased frustration, facilitated by a more structured approach and the anticipation of common errors.

Biomedical Research↗