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Biomedical subjects

P F Stalmeier

Publications and source records attributed to P F Stalmeier.

12 recordsLinked to original sources
PubMed2001

A fallacy of the multiplicative QALY model for low-quality weights in students and patients judging hypothetical health states.

OBJECTIVES: In quality-adjusted life-years (QALY) models, it is customary to weigh life-years with quality of life via multiplication. As a consequence, for positive health states a longer duration has more QALYs than a shorter duration (i.e., longer is better). However, we have found that for poor health states, many prefer to live only a limited amount of time (i.e., longer is worse). Such preferences are said to be maximum endurable time (MET). In the present contribution, the following questions are asked: a) How low does the utility have to be in order for a MET to arise? and b) Do MET preferences occur when patients judge hypothetical health states? METHODS AND RESULTS: We reanalyzed data from 176 students for the hypothetical health states of "living with migraines" and "living with metastasized cancer." For utilities smaller than 0.7 (ranging from 0 to 1), the MET preference rate was larger than 50%. High MET preference rates were also found in two new studies on migraine and esophageal cancer patients, who evaluated hypothetical health states related to their disease. CONCLUSIONS: We discuss the interpretation of the MET preferences and the preference reversal phenomenon. Standard QALY models imply that longer is better. However, we find that more often, longer is worse for poorly evaluated health states. Consider the following question: are 3 years with a weight of 0.3 equally as valuable as 1 year with a weight of 0.9? Our results suggest that the 3-year period may be less valuable because for poor health, many will prefer a 1-year over a 3-year period.

Adult↗
PubMed1994

Visual search and segregation as a function of display complexity.

Complexity is proposed as an important psychological factor in search and segregation tasks. Displays were presented with target and nontarget areas that were each built up of one type of randomly rotated micropatterns. We manipulated experimentally (a) the complexity of the target elements, as measured by Garner's (1970) invariance criterion; (b) the complexity of the target region; (c) the complexity of the nontargets; and (d) the number of elements within a target region. The main result is that detectability increases when the within-region complexity of the target and the nontarget regions decreases. Furthermore, interactions between the target and nontarget areas affect detectability too: We found that search asymmetry is produced by the asymmetrical effect of complexity when target and nontarget areas are interchanged.

Adult↗
PubMed1993

A test of Levelt's second proposition for binocular rivalry.

Levelt's second proposition (1968) was tested by investigating the effect of increasing the stimulus strength on the ipsilateral mean dominance duration. In three experiments, three stimulus dimensions were investigated: luminance contrast, colour contrast, and motion velocity. We included an experiment similar to Levelt's own equipment, in which a reversed contrast stimulus was used. In all three experiments, including the Levelt disk-ring experiment, the proposition was rejected. We conclude that Levelt's proposition cannot always be generalized to a broad class of stimulus dimensions and therefore cannot be held against reciprocal inhibition models.

Adult↗
PubMed1991

Large color differences and selective attention.

Similarity data for large color differences, obtained with triadic comparisons, are presented. Approximately 63,000 judgments are collected. We have compared the performance of the CIELUV, the CIELAB, and the Optical Society of America's [symbol; see text] jg color spaces, using three different color sets and two instructions. For color sets containing large color differences in the isoluminant plane, the [symbol; see text] jg color space outperforms the CIELUV and CIELAB spaces. We also investigated the effects of selective attention and conclude that, for judgments of large color differences, selective attention leads to significant changes in the relative contribution of the brightness dimension on the one hand and the hue and saturation dimensions on the other hand.

Adult↗
PubMedDate not supplied

A review on family history of breast cancer: screening and counseling proposals for women with familial (non-hereditary) breast cancer.

With the aim to specify screening recommendations for women with familial (non-hereditary) breast cancer (FBC) we analysed 59 studies using quantitative methods of pooling. The pooled relative risk (RR) and cumulative probability were used to estimate breast cancer risk. The RRs for women with a family history of breast cancer in a first-degree relative was 2.03 (95% CI 1.09-2.22). The highest RR is observed for women with a family history and atypical hyperplasia in their breast biopsy specimen (RR = 10.87, 95% CI 6.05-19.69). A high cumulative probability before the age of 50 was only found for women with a combination of two risk factors: a family history and atypical hyperplasia, namely 19% (95% CI 11-33%). The cumulative probabilities of women aged 50 to 70 years who have a family history were between 11% (95% CI 9-13%, a family history in combination with age at first birth before 22 years) and 53% (95% CI 35-75%, a family history in combination with atypical hyperplasia). These high risks suggest that women over 50 years of age who have a family history of FBC have to be actively encouraged to participate in a screening program consisting of a biannual palpation by a specialist, an annual mammogram and a monthly self-control. Yearly screening is recommended for women under 50 years of age who have a family history and atypical hyperplasia. These recommendations remain valid until the effectiveness of such screening programs is assessed.

Aged↗
PubMedDate not supplied

Prophylactic mastectomy or screening in women suspected to have the BRCA1/2 mutation: a prospective pilot study of women's treatment choices and medical and decision-analytic recommendations.

BACKGROUND: Women suspected to have the BRCA1/2 mutation may choose between two management options: breast cancer screening and prophylactic mastectomy (PM). OBJECTIVES: To compare women's treatment choices with medical and decision-analytic recommendations and to explore variables related to the women's choices. METHODS: After provision of information, individual time-tradeoff values for the health outcome "living after PM" were assessed and incorporated into a decision-analytic model, which compared the management options PM and screening with respect to their effects on quality-adjusted life expectancy. RESULTS: Of the 54 women suspected to have the mutation, 51 completed the shared-decision-making procedure. Quality-adjusted life expectancy after PM management was longer for 67% of proven carriers and for 58% of women awaiting the DNA-test result. Twelve proven carriers made definitive treatment choices: eight (67%) chose PM and four (33%) chose screening. All carriers' treatment choices agreed with the normative decision-analytic recommendations. Four (33%) disagreed with the medical recommendations. Of the 36 women awaiting DNA-test results, 32 made hypothetical treatment choices. The agreement between these hypothetical treatment choices and the decision-analytic recommendations was good (78%). Combining data from all 48 women, being married (OR = 14.00, p = 0.006), having children (OR = 4.71, p = 0.02), low desire to participate (OR = 0.14, p = 0.004), high decisional stress (OR = 5.22, p = 0.01), a lower estimate of the "probability of cure for screen-detected breast cancer" (OR = 0.13, p = 0.004), and higher time-tradeoff values for PM (OR = 182, p < 0.0001) made a choice for PM more likely. CONCLUSIONS: The complete agreement between the decision-analytic recommendations and the carriers' choices suggests that women act in accordance with normative decision theory. The disagreement between the carriers' choices and the medical recommendations suggests that women's choices and physicians' recommendations were guided by different arguments. The strong association between time-tradeoff value and treatment choice suggests that the time-tradeoff is a valid method to assess preferences.

Adult↗
PubMedDate not supplied

What should be reported in a methods section on utility assessment?

BACKGROUND: The measurement of utilities, or preferences, for health states may be affected by the technique used. Unfortunately, in papers reporting utilities, it is often difficult to infer how the utility measurement was carried out. PURPOSE: To present a list of components that, when described, provide sufficient detail of the utility assessment. METHODS: An initial list was prepared by one of the authors. A panel of 8 experts was formed to add additional components. The components were drawn from 6 clusters that focus on the design of the study, the administration procedure, the health state descriptions, the description of the utility assessment method, the description of the indifference procedure, and the use of visual aids or software programs. The list was updated and redistributed among a total of 14 experts, and the components were judged for their importance of being mentioned in a Methods section. RESULTS: More than 40 components were generated. Ten components were identified as necessary to include even in an article not focusing on utility measurement: how utility questions were administered, how health states were described, which utility assessment method(s) was used, the response and completion rates, specification of the duration of the health states, which software program (if any) was used, the description of the worst health state (lower anchor of the scale), whether a matching or choice indifference search procedure was used, when the assessment was conducted relative to treatment, and which (if any) visual aids were used. The interjudge reliability was satisfactory (Cronbach's alpha = 0.85). DISCUSSION: The list of components important for utility papers may be used in various ways, for instance, as a checklist while writing, reviewing, or reading a Methods section or while designing experiments. Guidelines are provided for a few components.

Authorship↗
PubMedDate not supplied

Proportional heuristics in time tradeoff and conjoint measurement.

The time-tradeoff (TTO) test is widely used to measure quality of life for different health states. Subjects are asked to equate the value of living a given period in an inferior health state to the value of living a shorter period in good health. Applications of TTOs have been criticized based on the fact that the value of future life duration is taken as the future life duration itself. The authors show that for a health state in which a subject does not want to live longer than a specified amount of time, subjects' responses do not comply with the assumption that the value of the period in inferior health is equated to the value of the shorter period in good health. Actually, preference reversals with respect to such a health state point to the use of a proportional heuristic in the TTO test. Comparisons of the TTO test in these subjects with category scaling and difference measurements also favor a proportional interpretation of the TTO test. In tests based on conjoint measurement, these subjects also appear to use a proportional heuristic. Consequences of the use of the TTO test and conjoint measurement in quality-of-life models are discussed.

Adult↗
PubMedDate not supplied

Assessment of the time-tradeoff values for prophylactic mastectomy of women with a suspected genetic predisposition to breast cancer.

BACKGROUND: Female carriers of the breast-cancer-susceptibility genes BRCA1 and BRCA2 are at high risk for breast cancer (85%). They face the choice between prophylactic mastectomy (PM) and breast cancer screening. For this treatment choice, a shared-decision-making program was developed. In this program, the time tradeoff (TTO) was used to assess preferences for PM. PURPOSE: Assessment of the feasibility, constant proportional tradeoff, and reliability of using the TTO for this purpose. METHODS: Fifty-four women suspected to carry the BRCA1/2 mutation were provided with comprehensive relevant information. Their preferences for PM were assessed on two occasions. Discrepancies between preferences indicated by the two tests were resolved by testing a third time. The preferences assessed on the last occasion were used for individual decision analyses. In order to test constant proportional tradeoff, the TTO consisted of four items with different numbers of life years. RESULTS: Forty-two women (78%) completed the TTO twice and nine women (17%) performed the test a third time. Three women (5%) completed the TTO only once. The mean TTO value for PM at the last replication was 0.69 (SD=0.30). Violations of constant proportional tradeoff were significant: the largest tradeoffs were recorded for the shortest durations. Pearson's correlation coefficient between the TTO values for the two last sessions was 0.96. CONCLUSION: Assessment of individual preferences by the TTO in this patient group is feasible and reliable. Therefore, the TTO can be used in clinical settings to elicit treatment preferences of women proven or suspected to have a genetic predisposition to breast cancer.

Adult↗
PubMedDate not supplied

Evaluation of a shared decision making program for women suspected to have a genetic predisposition to breast cancer: preliminary results.

BACKGROUND: Women suspected to have a genetic predisposition to breast cancer face the difficult choice between regular breast cancer screening and prophylactic mastectomy. The authors developed a shared decision making program (SDMP) to support this decision. OBJECTIVES: To evaluate the SDMP in terms of practicality, beneficial effects, and patient satisfaction. DESIGN: A one-group pretest-posttest design was used. MEASURES: Decision uncertainty, decision burden, subjective knowledge, and risk comprehension were assessed before and after the SDMP. Additional measures were obtained for concepts related to breast cancer concern, desire to participate in the program, satisfaction, program acceptability, and emotional reaction to the program information. RESULTS: Seventy-two women, most of whom were awaiting the genetic test results, participated. Decision uncertainty (effect size d = 0.37) and decision burden (d = 0.41) were reduced by the SDMP. Subjective knowledge (averaged d = 0.94) and risk comprehension were improved. The women were satisfied with the SDMP and found its rationale acceptable. Women who had strong emotional reactions to the information benefited less from the SDMP, whereas women with strong desires to participate in the decision benefited more. CONCLUSIONS: There is a need to give patients more information, especially about prophylactic mastectomy and among gene carriers. Beneficial effects were observed irrespective of whether genetic status was known, suggesting that information concerning treatment options should be made available as soon as DNA testing begins. The better psychological outcomes of women with stronger desires to participate may arise because the desire to participate is characteristic of emotional stability.

Adult↗
PubMedDate not supplied

The discrepancy between risky and riskless utilities: a matter of framing?

Utilities differ according to whether they are derived from risky (gamble) and riskless (visual analog scale, time-tradeoff) assessment methods. The discrepancies are usually explained by assuming that the utilities elicited by risky methods incorporate attitudes towards risk, whereas riskless utilities do not. In (cumulative) prospect theory, risk attitude is conceived as consisting of two components: a decision-weight function (attentiveness to changes in, or sensitivity towards, chance) and a utility function (sensitivity towards outcomes). The authors' data suggest that a framing effect is a hitherto unrecognized and important factor in causing discrepancies between risky and riskless utilities. They collected risky evaluations with the gamble method, and riskless evaluations with difference measurement. Risky utilities were derived using expected-utility theory and prospect theory. With the latter approach, sensitivity towards outcomes and sensitivity towards chance are modeled separately. When the hypothesis that risky utilities from prospect theory coincide with riskless utilities was tested, it was rejected (n = 8, F(1,7) = 132, p = 0.000), suggesting that a correction for sensitivity towards chance is not sufficient to resolve the difference between risky and riskless utilities. Next, it was assumed that different gain/loss frames are induced by risky and riskless elicitation methods. Indeed, identical utility functions were obtained when the gain/loss frames were made identical across methods (n = 7), suggesting that framing was operative. The results suggest that risky and riskless utilities are identical after corrections for sensitivity towards chance and framing.

Analysis of Variance↗