Biomedical subjects

L A Lenert

Publications and source records attributed to L A Lenert.

48 records · Page 3Linked to original sources

PubMedDate not supplied

Automated computer interviews to elicit utilities: potential applications in the treatment of deep venous thrombosis.

OBJECTIVE: To assess the practicality of an automated computer interview as a method to assess preferences for use in decision making. To assess preferences for outcomes of deep vein thrombosis (DVT) and its treatment. STUDY DESIGN: A multimedia program was developed to train subjects in the use of different preference assessment methods, presented descriptions of mild post-thrombotic syndrome (PTS), severe PTS and stroke and elicited subject preferences for these health states. This instrument was used to measure preferences in 30 community volunteers and 30 internal medicine physicians. We then assessed the validity of subject responses and calculated the number of quality-adjusted life years (QALYs) for each individual for each alternative. RESULTS: All subjects completed the computerized survey instrument without assistance. Subjects generally responded positively to the program, with volunteers and physicians reporting similar preferences. Approximately 26.5% of volunteers and physicians had preferences that would be consistent with the use of thrombolysis. Individualization of therapy would lead to the most QALYs. CONCLUSIONS: Utilization of computerized survey instruments to elicit patient preferences appears to be a practical and valid approach to individualize therapy. Application of this method suggests that there may be many patients with DVT for whom treatment with a thrombolytic drug would be optimal.

Adult↗

PubMedDate not supplied

Rapid approximation of confidence intervals for Markov process decision models: applications in decision support systems.

OBJECTIVE: Develop the methodological foundation for interactive use of Markov process decision models by patients and physicians at the bedside. DESIGN: Monte Carlo simulation studies of a decision model comparing two treatments for benign prostatic hypertrophy: watchful waiting (WW) and transurethral prostatectomy (TUR). MEASUREMENTS: The 95% confidence interval (CI) for the mean of the Markov model; the correlation of a linear approximation with the full Markov model; the predictive performance of the approximation; the information index of specific utilities in the model. RESULTS: The 95% CI for the gain in utility with initial TUR was -1.4 to 19.0 quality-adjusted life-months. A multivariate linear model had an excellent fit to the predictions of the Markov model (R2 = 0.966). In an independent data set, the linear model also had a high correlation with the full Markov model (R2 = 0.967); its predictions were unbiased (p = 0.597, paired t-test); and, in 96.4% of simulated cases, its treatment recommendation was the same. CONCLUSION: Using the linear model, it was possible to efficiently compute which health state had the largest contribution to the variance of the decision model. This is the most informative utility value to elicit next. The most informative utility at any point in a sequence changed depending on utilities previously entered into the model. A linear model can be used to approximate the predictions of a Markov process decision model.

Aged↗

PubMedDate not supplied

Quality-of-life research on the Internet: feasibility and potential biases in patients with ulcerative colitis.

OBJECTIVE: The World Wide Web (WWW) is a new communications medium that permits investigators to contact patients in nonmedical settings and study the effects of disease on quality of life through self-administered questionnaires. However, little is known about the feasibility and, what is more important, the validity of this approach. An on-line survey for patients with ulcerative colitis (UC) and patients whose UC had been treated with surgical procedures was developed. To understand how patients on the WWW might differ from those in practice and the potential biases in conducting epidemiological research in volunteers recruited on the Internet, post-surgery patients who responded to the WWW survey were compared with those in a surgical practice. SETTING: The Internet and private practice surgical clinic. MAIN OUTCOMES: Scores from the Short form 36 (SF-36) Health Assessment Questionnaire and the Self-Administered Inflammatory Bowel Disease Questionnaire (IBDQ). RESULTS: Over a 5-month period, 53 post-surgery patients enrolled in the Internet study; 47 patients from a surgical clinic completed the same computer-based questionnaire. Surgically treated patients on the WWW were younger than their clinic counterparts (median age category 35-44 years vs. 45-54 years, p = 0.01) but more ill with a lower summary IBDQ score (168 vs. 186, p = 0.019) and lower health status across almost all dimensions of the SF-36 (p = 0.016). CONCLUSIONS: It is feasible to conduct epidemiological research on the effects of UC on quality of life on the Web; however, systematic differences in disease activity between volunteer patients on the WWW and "in the clinic" may limit the applicability of results.

Adult↗

PubMedDate not supplied

Use of meta-analytic results to facilitate shared decision making.

OBJECTIVES: Describe and evaluate an Internet-based approach to patient decision support using mathematical models that predict the probability of successful treatment on the basis of meta-analytic summaries of the mean and standard deviation of symptom response. DESIGN: An Internet-based decision support tool was developed to help patients with benign prostatic hypertrophy (BPH) determine whether they wanted to use alpha blockers. The Internet site incorporates a meta-analytic model of the results of randomized trials of the alpha blocker terazosin. The site describes alternative treatments for BPH and potential adverse effects of alpha blockers. The site then measures patients' current symptoms and desired level of symptom reduction. In response, the site computes and displays the probability of a patient's achieving his objective by means of terazosin or placebo treatment. SETTING: Self-identified BPH patients accessing the site over the Internet. MAIN OUTCOME MEASURES: Patients' perceptions of the usefulness of information. RESULTS: Over a three-month period, 191 patients who were over 50 years of age and who reported that they have BPH used the decision support tool. Respondents had a mean American Urological Association (AUA) score of 18.8 and a desired drop in symptoms of 10.1 AUA points. Patients had a 40 percent chance of achieving treatment goals with terazosin and a 20 percent chance with placebo. Patients found the information useful (93 percent), and most (71 percent) believed this type of information should be discussed before prescribing medications. CONCLUSIONS: Interactive meta-analytic summary models of the effects of pharmacologic treatments can help patients determine whether a treatment offers sufficient benefits to offset its risks.

Adrenergic alpha-Antagonists↗

PubMedDate not supplied

The risks of multimedia methods: effects of actor's race and gender on preferences for health states.

OBJECTIVE: While the use of multimedia methods in medical education and decision support can facilitate learning, it also has certain hazards. One potential hazard is the inadvertent triggering of racial and gender bias by the appearance of actors or patients in presentations. The authors hypothesized that race and gender affect preferences. To explore this issue they studied the effects of actors' race and gender on preference ratings for health states that include symptoms of schizophrenia. DESIGN: A convenience sample of patients with schizophrenia, family members of patients, and health professionals was used. Participants were randomly assigned to rate two health states, one portrayed by either a man of mixed race (Hispanic-black) or a white man and the second portrayed by either a white woman or a white man. MEASUREMENTS: Visual analog scale (VAS) and standard gamble ratings of health state preferences for health states that include symptoms of mild and moderate schizophrenia. RESULTS: Studies of the effects of the race of the actor (n = 114) revealed that racial mismatch between the actor and the participant affected the participant's preferences for health states. Ratings were lower when racial groups differed (mean difference, 0.098 for visual analog scale ratings and 0.053 lower in standard gamble, P = 0.006 for interactions between the race of the subject and the actor). In studies of the effects of a female actress on ratings (n = 117), we found no evidence of a corresponding interaction between the gender of the actor and the study participant. Rather, an interaction between actor's gender and method of assessment was observed. Standard gamble ratings (difference between means, 0.151), but not visual analog scale ratings (difference, 0.005), were markedly higher when the state was portrayed by the actress (P = 0.003 for interactions between actor's gender and method of preference assessment). Differential effects on standard gamble ratings suggest that an actor's gender may influence the willingness of viewers to gamble to gain health benefits (or risk attitude). CONCLUSIONS: Educators and researchers considering the use of multimedia methods for decision support need to be aware of the potential for the race and gender of patients or actors to influence preferences for health states and thus, potentially, medical decisions.

Analysis of Variance↗

PubMedDate not supplied

Utility elicitation using single-item questions compared with a computerized interview.

BACKGROUND: The use of a simpler procedure for the measurement of utilities could affect primarily the variance or both the mean and the variance of measurements. In the former case, simpler methods would be useful for population studies of preferences; however, in the latter, their use for such studies might be problematic. PURPOSE: The purpose of this study was to compare the results of utility elicitation using single-item questions to computer elicitation using the Ping-Pong search procedure. METHODS: In a convenience sample of 149 primary care patients with symptoms of depression, the authors measured and compared standard gamble (SG) utilities elicited using a single-item "open question" to SG elicitations performed using a computerized interview procedure. Elicitations were performed 1 to 2 weeks apart to minimize memory effects. RESULTS: More than 90% of persons with utilities of 1.0 to the single-item standard gamble had utilities of less than 1.0 on the computer SG instrument. Consistent with this finding, the mean utilities were lower in computer interviews (0.80 vs. 0.90; P < 0.0001 for differences). Within subjects, utility measures had only a fair degree of correlation (r = 0.54). CONCLUSIONS: Use of single-item questions to elicit utilities resulted in less precise estimates of utilities that were upwardly biased relative to those elicited using a more complex search procedure.

Adult↗

PubMedDate not supplied

iMPACT3: Internet-based development and administration of utility elicitation protocols.

iMPACT3 (Internet Multimedia Preference Assessment Instrument Construction Tool, version 3) is a software development environment that helps researchers build Internet-capable multimedia utility elicitation software programs. The program is a free, openly accessible Web site (http.// preferences.ucsd.edu/impact3/asp). To develop a utility elicitation software program using iMPACT3, a researcher selects modular protocol components from a library and custom tailors the components to the details of his or her research protocol. iMPACT3 builds a Web site implementing the protocol and downloads it to the researcher's computer. In a study of 75 HIV-infected patients, an iMPACT3-generated protocol showed substantial evidence of construct validity and good internal consistency (logic error rates of 4% to 10% and procedural invariance error rates of 10% to 28%, depending on the elicitation method) but only fair 3- to 6-week test-retest reliability (intraclass correlation coefficient= 0.42 to 0.55). Further work may be needed on specific utility assessment procedures, but this study's results confirm iMPACT3's feasibility in facilitating the collection of health state utility data.

Adult↗

PubMedDate not supplied

Developing and testing a multimedia presentation of a health-state description.

Quality-adjustment weights for health states are an essential component of cost-utility analysis (CUA). Quality-adjustment weights are obtained by presenting large numbers of subjects with multiattribute descriptions of health states for rating. Comprehending multiattribute health states is a difficult task for most respondents. The authors hypothesized that multimedia (MM) presentation using computers might facilitate this task better than would a paper-based text (Text). To test this hypothesis, they developed closely matched MM and Text descriptions of health states in the first-person narrative style, and developed a method of testing the presentation of a health state. Subjects were randomized to exposure to either MM or Text and subject recall of the health state and recognition of features of the health state were tested. How well defined the preferences of the subjects were after each presentation method was assessed by having the subjects mark on a double-anchored visual-analog scale the "best" and "worst" they believed the quality of life in the health state might be. MM subjects had better recall (11.85 vs 9.44 of a total of 24 meaning units, p = 0.098) and better recognition (4.71 vs 4.22, p = 0.08). The average interval between the "best" and "worst" ratings was shorter for the MM subjects (2.19 cm vs 3.26 cm, p = 0.12).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Incorporating risk attitude into Markov-process decision models: importance for individual decision making.

Most decision models published in the medical literature take a risk-neutral perspective. Under risk neutrality, the utility of a gamble is equivalent to its expected value and the marginal utility of living a given unit of time is the same regardless of when it occurs. Most patients, however, are not risk-neutral. Not only does risk aversion affect decision analyses when tradeoffs between short- and long-term survival are involved, it also affects the interpretation of time-tradeoff measures of health-state utility. The proportional time tradeoff under- or overestimates the disutility of an inferior health state, depending on whether the patient is risk-seeking or risk-averse (it is unbiased if the patient is risk-neutral). The authors review how risk attitude with respect to gambles for survival duration can be incorporated into decision models using the framework of risk-adjusted quality-adjusted life years (RA-QALYs). They present a simple extension of this framework that allows RA-QALYs to be calculated for Markov-process decision models. Using a previously published Markov-process model of surgical vs expectant treatment for benign prostatic hypertrophy (BPH), they show how attitude towards risk affects the expected number of QALYs calculated by the model. In this model, under risk neutrality, surgery was the preferred option. Under mild risk aversion, expectant treatment was the preferred option. Risk attitude is an important aspect of preferences that should be incorporated into decision models where one treatment option has upfront risks of morbidity or mortality.

Aged↗

PubMedDate not supplied

The effect of search procedures on utility elicitations.

OBJECTIVE: Elicited preferences for health states vary among scaling methods, manners of describing health states, and other features of the elicitation process. The authors examined the effects of changing the search procedure for a subject's utility on mean utility values. METHODS: A randomized controlled trial of two search procedures (titration and "ping-pong") using two otherwise identical computer programs that describe health states related to Gaucher's disease, then measuring subjects' preferences. SETTING: Paid, healthy volunteers recruited from the community through advertisements. RESULTS: The mean time tradeoff (TTO) and standard gamble (SG) utility values for life with severe anemia and splenomegaly and life with chronic bone pain from Gaucher's disease were between 0.10 and 0.15 higher with the titration search procedure than with the ping-pong procedure. Effects of the search procedure were additive with variability due to scaling methods, resulting in mean differences in utility ratings for the same health state of as much as 0.28 among procedures and scaling methods. Effects of search procedures on utility values persisted on repeated testing at week 2 and week 3; there was no evidence of convergence to a single "true" utility value over time. CONCLUSIONS: The procedure used to search for subjects' utility values strongly influences the results of preference-assessment experiments. Effects of search procedures persist on repeated testing. The results suggest that utility values are heavily influenced by, if not created during, the process of elicitation. Thus, utility values elicited using different search procedures may not be directly comparable.

Adult↗

PubMedDate not supplied

Health values and prospect theory.

Health values are important components of medical decisions. Experimental data suggest that people value health in complex and dynamic ways. Prospect theory is a descriptive theory of choice that may accurately characterize how people assign values to health states. The authors first provide background on prospect theory and how it can be applied to health values. Next, they review the relevant health research and find mixed support for prospect theory. Last, they discuss implications of prospect theory for cost-effectiveness analysis. The application of prospect theory to health deserves further research because it may help clarify the link between health and values.

Attitude to Health↗

PubMedDate not supplied

Effects on preferences of violations of procedural invariance.

BACKGROUND: In studies of health preferences, utilities for hypothetical health states cannot always be successfully measured. One marker for unsuccessful measurement is violation of "procedural invariance": when the ranking of two health states varies across assessment procedures. Using preference values based on unsuccessful measurement may result in misinterpretation of patients' attitudes about health. OBJECTIVE: The authors sought to determine whether people who violated procedural invariance had different preferences than people who satisfied it. METHODS: They performed secondary analyses of three completed studies that used the same two assessment procedures, identifying participants who violated procedural invariance and comparing the mean standard gamble (SG) and visual analog scale (VAS) scores of violators and satisfiers. PARTICIPANTS: Experiment 1, 30 healthy volunteers and 30 patients with cardiac arrhythmias; experiment 2, 139 patients with depressive illness; experiment 3, 98 family members of patients with schizophrenia. RESULTS: Rates of violation of procedural invariance ranged from 16% to 32%. Violation of procedural invariance was not associated with age, education level, race, or gender. Subjects with violations of procedural invariance had, in general, less ability to discriminate among states and less reliable VAS and SG measurements, and sometimes had different mean SG and VAS values. CONCLUSIONS: Violation of procedural invariance of preferences across scaling methods may be a signal for failure of the measurement process. Researchers should test for procedural invariance and consider reporting data separately for satisfiers and violators.

Aged↗