Biomedical subjects

G B Hazen

Publications and source records attributed to G B Hazen.

6 recordsLinked to original sources

PubMed1999

A Bayesian approach to sensitivity analysis.

Sensitivity analysis has traditionally been applied to decision models to quantify the stability of a preferred alternative to parametric variation. In the health literature, sensitivity measures have traditionally been based upon distance metrics, payoff variations, and probability measures. We advocate a new approach based on information value and argue that such an approach is better suited to address the decision-maker's real concerns. We provide an example comparing conventional sensitivity analysis to one based on information value. This article is a US government work and is in the public domain in the United States.

Bayes Theorem↗

PubMed1996

A cost-effectiveness analysis of total hip arthroplasty for osteoarthritis of the hip.

OBJECTIVE: To quantify the trade-off between the expected increased short- and long-term costs and the expected increase in quality-adjusted life expectancy (QALE) associated with total hip arthroplasty (THA) for persons with functionally significant hip osteoarthritis. DESIGN: A cost-effectiveness study was performed from the societal perspective by constructing stochastic tree, decision analytic models designed to estimate lifetime functional outcomes and costs of THA and nonoperative managements. MAIN OUTCOME MEASURES: A modified four-state American College of Rheumatology functional status classification was used to measure effectiveness. These functional classes were assigned utility values to allow the relative effectiveness of THA to be expressed in quality-adjusted life years (QALYs). Lifetime costs included costs associated with primary and potential revision surgeries and long-term care costs associated with the functionally dependent class. DATA USED IN THE COST-EFFECTIVENESS MODEL: Probability and incidence rate data were summarized from the literature. The THA hospital cost data were obtained from local teaching hospitals' cost accounting systems. Estimates of recurring medical costs for functionally significant hip osteoarthritis and for custodial care were derived from the literature. RESULTS: The THA cost-effectiveness ratio increases with age and is higher for men than for women. In the base-case scenario for 60-year-old white women who have functionally significant but not dependent hip osteoarthritis, the model predicts that THA is cost saving because of the high costs of custodial care associated with dependency due to worsening hip osteoarthritis and that the procedure increases QALE by about 6.9 years. In the base-case scenario for men aged 85 years and older, the average lifetime cost associated with THA is $9100 more than nonoperative management, with an average increase in QALE of about 2 years. Thus, the THA cost-effectiveness ratio for men aged 85 years and older is $4600 per QALY gained, less than that of procedures intended to extend life such as coronary artery bypass surgery or renal dialysis. Worst-case analysis suggests that THA remains minimally cost-effective for this oldest age category ($80,000/QALY) even if probabilities, rates, utilities, costs, and the discount rate are simultaneously varied to extreme values that bias the analysis against surgery. CONCLUSIONS: For persons with hip osteoarthritis associated with significant functional limitation, THA can be cost saving or, at worst, cost- effective in improving QALE when both short- and long-term outcomes are considered. Further research is needed to determine whether this procedure is actually being used in this cost-effective manner, especially in older age categories.

Age Factors↗

PubMedDate not supplied

Continuous-risk utility assessment in medical decision making.

The authors argue that for risky medical treatment decisions, conventional utility assessment techniques are inadequate due to their emphasis on unrealistic risk magnitudes and sure consequences, leading to assessment questions that are unfamiliar to most patients, have little educational value, and do not reliably extend to the application at hand. As an alternative, medical utility assessments should be performed in a continuous-risk domain with risk levels matching those of the actual decision problem. In support of this position, the authors describe an empirical study that compares the responses of subjects under a conventional assessment protocol with those of subjects under a continuous-risk utility assessment protocol. Preliminary results show that conventional assessment protocols result in significantly lower estimates of the degrees of risk aversion compared with a more realistic continuous-risk protocol.

Attitude of Health Personnel↗

PubMedDate not supplied

Stochastic trees: a new technique for temporal medical decision modeling.

This paper introduces stochastic trees, a new modeling approach for the class of medical decision problems in which risks of mortality and morbidity may extend over time. A stochastic tree may be regarded as a continuous-time version of a Markov-cycle tree, or alternately, as a multi-state DEALE model. Optimal decisions in stochastic trees can be determined by rollback, much in the same fashion as decision trees. The author discusses how age-dependent mortality rates and declining incidence rates may be modeled using stochastic trees. Concepts are illustrated using examples from the medical literature. It is argued that stochastic trees possess important advantages over Markov-cycle trees for medical decision modeling.

Age Factors↗

PubMedDate not supplied

Factored stochastic trees: a tool for solving complex temporal medical decision models.

The stochastic tree is a continuous-time version of a Markov-cycle tree, useful for constructing and solving medical decision models in which risks of mortality and morbidity may extend over time. Stochastic trees have advantages over Markov-cycle trees in graphic display and computational solution. Like the decision tree or Markov-cycle tree, stochastic tree models of complex medical decision problems can be too large for convenient graphic formulation and display. This paper introduces the notion of factoring a large stochastic tree into simpler components, each of which may be easily displayed. It also shows how the rollback solution procedure for unfactored stochastic trees may be conveniently adapted to solve factored trees. These concepts are illustrated using published examples from the medical literature.

Decision Trees↗

PubMedDate not supplied

Sensitivity analysis and the expected value of perfect information.

Measures of decision sensitivity that have been applied to medical decision problems were examined. Traditional threshold proximity methods have recently been supplemented by probabilistic sensitivity analysis, and by entropy-based measures of sensitivity. The authors propose a fourth measure based upon the expected value of perfect information (EVPI), which they believe superior both methodologically and pragmatically. Both the traditional and the newly suggested sensitivity measures focus entirely on the likelihood of decision change without attention to corresponding changes in payoff, which are often small. Consequently, these measures can dramatically overstate problem sensitivity. EVPI, on the other hand, incorporates both the probability of a decision change and the marginal benefit of such a change into a single measure, and therefore provides a superior picture of problem sensitivity. To lend support to this contention, the authors revisit three problems from the literature and compare the results of sensitivity analyses using probabilistic, entropy-based, and EVPI-based measures.

Adult↗