Expert judgments of pandemic influenza risks.

Structured surveys were conducted with 19 medical experts, and 17 non-medical experts in related fields, attending a meeting about pandemic influenza. Respondents gave quantitative judgments for key variables potentially affecting the extent of a possible H5N1 pandemic. The medical experts saw about a 15% (median) chance of efficient human-to-human transmission, in the next 3 years. Should it occur, they saw almost no chance of there being adequate vaccines or antiviral responses. They saw varying chances of six other mitigation strategies reducing the threat, expressing the greatest faith in improved surveillance. Compared to the medical experts, the non-medical experts saw much higher chances of both human-to-human transmission and of effective vaccine and antiviral responses being available. The medical experts and the non-medical experts had similar, dire predictions for the extent of casualties, should transmission occur in the next 3 years. Their responses to open-ended questions revealed some of the theories underlying these beliefs.

Mental models of women with breast implants: local complications.

Twenty-five women with breast implants participated in semistructured interviews designed to reveal their "mental models" of the processes potentially causing local (i.e., nonsystemic) problems. The authors analyzed their responses in terms of an "expert model," circumscribing scientifically relevant information. Most of the women interviewed had something to say about most elements in the expert model. Nonetheless, gaps in their mental models undermined decision making about their implants. One woman misunderstood the terms used by the medical community to describe implant failure (e.g., rupture, leak, and bleed). Another exaggerated the implants' vulnerability to direct impacts, such as car accidents. Participants also overestimated their ability to detect localized problems and to select medical remedies. Although they were generally satisfied with their own implants, many participants were dissatisfied with the decision-making processes that lead to their choice. Their interviews are interpreted by the form and content of communications that women with implants need to help them manage their health decisions better.

Evaluating the effectiveness of risk-reduction strategies for consumer chemical products.

Communication about risks offers a voluntary approach to reducing exposure to pollutants. Its adequacy depends on its impact on behavior. Estimating those impacts first requires characterizing current activities and their associated risk levels, and then predicting the effectiveness of risk-reduction strategies. Characterizing the risks from chemical consumer products requires knowledge of both the physical and the behavioral processes that influence exposures. This article presents an integrated approach that combines consumer interviews, users' beliefs and behaviors, and quantitative exposure modeling. This model was demonstrated in the context of consumer exposure to a methylene chloride-based paint stripper, showing how it could be used to evaluate current levels of risk and predict the effectiveness of proposed voluntary risk-reduction strategies.

Women's views on breast cancer risk and screening mammography: a qualitative interview study.

BACKGROUND: To promote informed decision making about mammography, clinicians are urged to present women with complete, relevant information about breast cancer and screening. Understanding women's current beliefs may help guide such efforts by uncovering misunderstandings, conceptual gaps, and areas of concern. OBJECTIVE: The authors sought to learn how women view breast cancer, their personal risk of breast cancer, and how screening mammography affects that risk. METHODS: Forty-one open-ended semistructured telephone interviews with women selected from a national database by quota sampling to ensure a wide range in demographics of the participants. RESULTS: Almost all respondents viewed breast cancer as a uniformly progressive disease that begins in a silent curable form (typically found by mammograms) and, unless treated early, invariably grows, spreads, and kills. Some women felt that any abnormality found must be treated, even if it was not malignant. None had heard of potentially nonprogressive cancers, and when informed, most felt that the uncertain prognosis of such lesions reinforced the need to find and treat disease as soon as possible. Women expressed a wide range of views about their personal risk of breast cancer. Although some saw breast cancer as a central threat to their health, many others cited heart disease, other cancers, violence, and trauma as greater concerns. Most recognized the importance of "uncontrollable" factors for breast cancer such as age, sex, family history, and genetics. However, other "controllable" factors with little or no demonstrated link to breast cancer (e.g., smoking, diet, toxic exposures, "bad attitudes") were given equal or greater prominence, suggesting that many women feel considerable personal responsibility for their level of breast cancer risk. Similarly, although women recognized that mammography was not perfect, almost all believed that failure to have mammograms put one at risk for premature and preventable death. When asked how mammography worked, almost all repeated the message that "early detection saves lives," suggesting that advanced cancer (and perhaps most cancer deaths) reflected a failure of early detection. The belief in the benefit of early detection was so strong that some women advocated scaring other women into getting mammograms because it is "better to be safe than sorry." CONCLUSIONS: Women view breast cancer as a uniformly progressive disease rarely curable unless caught early. The exaggerated importance many attribute to a variety of controllable factors in modifying personal risk and the "danger" seen in failing to have mammograms may lead women diagnosed with breast cancer to blame themselves.

A deliberative method for ranking risks (I): Overview and test bed development.

Risk ranking offers a potentially powerful means for gathering public input to help set risk-management priorities. In most rankings conducted to date, the categories and attributes used to describe the risks have varied widely, the materials and procedures have not been designed to facilitate comparisons among risks on all important attributes, and the validity and reproducibility of the resulting rankings have not been assessed. To address these needs, a risk-ranking method was developed in which risk experts define and categorize the risks to be ranked, identify the relevant risk attributes, and characterize the risks in a set of standardized risk summary sheets, which are then used by lay or other groups in structured ranking exercises. To evaluate this method, a test bed involving 22 health and safety risks in a fictitious middle school was created. This article provides an overview of the risk-ranking method and describes the challenges faced in designing the middle school test bed. A companion article in this issue reports on the validity of the ranking procedures and the level of agreement among risk managers regarding ranking of risks and attributes.

A deliberative method for ranking risks (II): Evaluation of validity and agreement among risk managers.

A deliberative method for ranking risks was evaluated in a study involving 218 risk managers. Both holistic and multiattribute procedures were used to assess individual and group rankings of health and safety risks facing students at a fictitious middle school. Consistency between the rankings that emerged from these two procedures was reasonably high for individuals and for groups, suggesting that these procedures capture an underlying construct of riskiness. Participants reported high levels of satisfaction with their groups' decision-making processes and the resulting rankings, and these reports were corroborated by regression analyses. Risk rankings were similar across individuals and groups, even though individuals and groups did not always agree on the relative importance of risk attributes. Lower consistency between the risk rankings from the holistic and multiattribute procedures and lower agreement among individuals and groups regarding these rankings were observed for a set of high-variance risks. Nonetheless, the generally high levels of consistency, satisfaction, and agreement suggest that this deliberative method is capable of producing risk rankings that can serve as informative inputs to public risk-management decision making.

US women's attitudes to false-positive mammography results and detection of ductal carcinoma in situ: cross-sectional survey.

OBJECTIVE: To determine women's attitudes and knowledge of both false-positive mammography results and the detection of ductal carcinoma in situ after screening mammography. DESIGN: Cross-sectional survey. SETTING: United States. PARTICIPANTS: A total of 479 women aged 18 to 97 years who did not report a history of breast cancer. Main outcome measures Attitudes and knowledge about false-positive results and the detection of ductal carcinoma in situ after screening mammography. RESULTS: Women were aware that false-positive results do occur. Their median estimate of the false-positive rate for 10 years of annual screening was 20% (25th percentile estimate, 10%; 75th percentile estimate, 45%). The women were highly tolerant of false-positive results: 63% thought that 500 or more false-positives per life saved was reasonable, and 37% would tolerate a rate of 10,000 or more. Women who had had a false-positive result (n = 76) expressed the same high tolerance: 30 (39%) would tolerate 10,000 or more false-positives. In all, 62% of women did not want to take false-positive results into account when deciding about screening. Only 8% of women thought that mammography could harm a woman without breast cancer, and 94% doubted the possibility of nonprogressive breast cancers. Few had heard of ductal carcinoma in situ, a cancer that may not progress, but when informed, 60% of women wanted to take into account the possibility of it being detected when deciding about screening. CONCLUSIONS: Women are aware of false-positive results and seem to view them as an acceptable consequence of screening mammography. In contrast, most women are unaware that screening can detect cancers that may never progress but think that such information would be relevant. Education should perhaps focus less on false-positive results and more on the less-familiar outcome of the detection of ductal carcinoma in situ.

An integrated risk model of a drinking-water-borne cryptosporidiosis outbreak.

A dynamic risk model is developed to track the occurrence and evolution of a drinking-water-borne cryptosporidiosis outbreak. The model characterizes and integrates the various environmental, medical, institutional, and behavioral factors that determine outbreak development and outcome. These include contaminant delivery and detection, water treatment efficiency, the timing of interventions, and the choices that people make when confronted with a known or suspected risk. The model is used to evaluate the efficacy of alternative strategies for improving risk management during an outbreak, and to identify priorities for improvements in the public health system. Modeling results indicate that the greatest opportunity for curtailing a large outbreak is realized by minimizing delays in identifying and correcting a drinking-water problem. If these delays cannot be reduced, then the effectiveness of risk communication in preemptively reaching and persuading target populations to avoid exposure becomes important.

Traffic accident statistics and risk perceptions in Japan and the United States.

Several recent studies have concluded that Japan and the US have different risk cultures. This study examines the actual risk environments faced by citizens in the two countries, in the domain of traffic safety, as a possible source of differences in risk perceptions. The study contrasts traffic-accident risks from several points of view (e.g. car drivers, motorcyclists, bicyclists and pedestrians) and risk statistics (e.g. death rates, relative fatality risks, and accident lethality). Results clarify the traffic risks in the two countries and confirm their potential for explaining cross-national differences in risk perceptions.

A new scale for assessing perceptions of chance: a validation study.

BACKGROUND: Clinicians and researchers often wish to know how patients perceive the likelihoods of health risks. Little work has been done to develop and validate scales and formats to measure perceptions of event probabilities, particularly low probabilities (i.e., <1%). OBJECTIVE: To compare a new visual analog scale with three benchmarks in terms of validity and reliability. DESIGN: Survey with retest after approximately two weeks. Respondents estimated the probabilities of six events with the new scale, which featured a "magnifying glass" to represent probabilities between 0 and 1% on a logarithmic scale. Participants estimated the same probabilities on three benchmarks: two linear visual analog scales (one labeled with words, one with numbers) and a "1 in x" scale. SUBJECTS: 100 veterans and family members and 107 university faculty and students. MEASURES: For each scale, the authors assessed: 1) validity-the correlation between participants' direct rankings (i.e., numbering them from 1 to 6) and scale-derived rankings of the relative probabilities of six events; 2) test-retest reliability-the correlation of responses from test to retest two weeks later; 3) usability (missing/ incorrect responses, participant evaluation). RESULTS: Both the magnifier and the two linear scales outperformed the "1 in x" scale on all criteria. The magnifier scale performed about as well as the two linear visual analog scales for validity (correlation between direct and scale-derived rankings = 0.72), reliability (test-retest correlation = 0.55), and usability (2% missing or incorrect responses, 65% rated it easy to use). 62% felt the magnifier scale was a "very good or good" indicator of their feelings about chance. The magnifier scale facilitated expression of low-probability judgments. For example, the estimated chance of parenting sextuplets was orders of magnitude lower on the magnifier scale (median perceived chance 10(-5)) than on its linear counterpart (10(-2)). Participants' assessments of high-probability events (e.g., chance of catching a cold in the next year) were not affected by the presence of the magnifier. CONCLUSIONS: The "1 in x" scale performs poorly and is very difficult for people to use. The magnifier scale and the linear number scale are similar in validity, reliability, and usability. However, only the magnifier scale makes it possible to elicit perceptions in the low-probability range (<1%).

Setting risk priorities: a formal model

This article presents a model designed to capture the major aspects of setting priorities among risks, a common task in government and industry. The model has both design features, under the control of the rankers (e.g., how success is evaluated), and context features, properties of the situations that they are trying to understand (e.g., how quickly uncertainty can be reduced). The model is demonstrated in terms of two extreme ranking strategies. The first, sequential risk ranking, devotes all its resources, in a given period, to learning more about a single risk, and its place in the overall ranking. This strategy characterizes the process for a society (or organization or individual) that throws itself completely into dealing with one risk after another. The other extreme strategy, simultaneous risk ranking, spreads available resources equally across all risks. It characterizes the most methodical of ranking exercises. Given ample ranking resources, simultaneous risk ranking will eventually provide an accurate set of priorities, whereas sequential ranking might never get to some risks. Resource constraints, however, may prevent simultaneous rankers from examining any risk very thoroughly. The model is intended to clarify the nature of ranking tasks, predict the efficacy of alternative strategies, and improve their design.

The effect of question format on measured HIV/AIDS knowledge: detention center teens, high school students, and adults.

This study examines the effect of question format on HIV/AIDS knowledge assessed in teens in a detention center, public high school students, and adults. Multiple-choice items were taken from a Red Cross questionnaire and were transformed into open-ended and true/false/don't know formats. Each respondent received an open-ended and a structured version of the test (consisting of multiple-choice and true/false/don't know items). Format effects varied by group and order of presentation: High school students and adults performed better on the open-ended questions if they had answered the structured versions first-suggesting that the structured questions provided these respondents with unintended cues. Detention center youths did not benefit from having answered the structured items, and scored especially low on the open-ended questions. However, they did almost as well as the other groups with the true/false/don't know format. Implications are discussed for measuring HIV/AIDS knowledge and evaluating educational programs for different target audiences.

Modeling methylene chloride exposure-reduction options for home paint-stripper users.

Home improvement is a popular activity, but one that can also involve exposure to hazardous substances. Paint stripping is of particular concern because of the high potential exposures to methylene chloride, a solvent that is a potential human carcinogen and neurotoxicant. This article presents a general methodology for evaluating the effectiveness of behavioral interventions for reducing these risks. It doubles as a model that assesses exposure patterns, incorporating user time-activity patterns and risk-mitigation strategies. The model draws upon recent innovations in indoor air-quality modeling to estimate exposure through inhalation and dermal pathways to paint-stripper users. It is designed to use data gathered from home paint-stripper users about room characteristics, amount of stripper used, time-activity patterns and exposure-reduction strategies (e.g., increased ventilation and modification in the timing of stripper application, scraping, and breaks). Results indicate that the effectiveness of behavioral interventions depends strongly on characteristics of the room (e.g., size, number and size of doors and windows, base air-exchange rates). The greatest simple reduction in exposure is achieved by using an exhaust fan in addition to opening windows and doors. These results can help identify the most important information for product labels and other risk-communication materials.

Previous clinical diagnosis of chlamydia helps patients predict outcome of new chlamydia clinical test

Background: As part of an ongoing clinical trial evaluating the effectiveness of an intervention aimed at decreasing STDs in adolescent females, a host of different background measures were collected at baseline. These measures include self-reported behaviors, risk and probability estimates concerning STDs, self-reported prior medical diagnoses, and a Chlamydia trachomatis (Ct) infection assay, among other measures. This analysis examines participants' accuracy in estimating their own chance of chlamydia infection.Methods: Participants were 131 sexually active adolescent females, 79% black, 13% white, mean age 16 (range 13-19), who had been recruited from an adolescent health service. At the time of this study, participants were not primarily being seen for a clinical visit. Participants answered two questions that are examined here: The first asked, "What is the percent chance that you have chlamydia right now," accompanied by a visual scale ranging from 0% (no chance) to 100% (certainly). The second question asked, "In your life, have you ever been told by a doctor or nurse that you had chlamydia?" Following all questions a vaginal swab was collected by the participant, which was analyzed by polymerase chain reaction (PCR) for Ct. A multiple regression was performed, predicting the outcome of the chlamydia swab test using participants' estimates that they had chlamydia, their self-reported prior diagnosis with chlamydia (dichotomous), and the interaction between these two variables.Results: The regression F(3, 127) = 10.95, p <.01, revealed that participants' estimates of the chance that they had chlamydia significantly predicted outcome of the clinical test, t(127) = 3.34, p <.01. Previous diagnosis with chlamydia alone did not predict outcome of the clinical test, t(127) = -0.84, ns, but the interaction between the two variables significantly predicted clinical outcome, t(127) = -2.07, p <.05. A previous chlamydia diagnosis made participants' own estimates highly predictive of the clinical outcome; the estimates of those who had never been previously diagnosed with chlamydia had very little predictive power. Conclusions: Those participants who had prior experience with a chlamydia diagnosis were much more able to interpret their own risks and symptoms, and arrive at a very accurate estimate of the chance that they had a chlamydia infection. It is important to note that these participants were not seeking care at the time of this study, but that they had enough information to predict clinical outcome of a chlamydia test, especially those who had been diagnosed with chlamydia in the past. Arguably, these are they very patients who are most at risk for long-term sequelae of chlamydia infection, and asking (or having the patient ask) the relevant questions may increase the likelihood that they are identified and treated promptly, and early in the course of infection.

The long-term risks in the short-term benefits: perceptions of potentially addictive activities.

It is generally assumed that individuals who take risks with their health either underestimate the magnitude of those risks or seek some benefit. This study assessed whether risk taking might also result from underestimating the benefits. In Study 1, lower estimates of the pleasure of drug use and risk of addiction were significantly related to increased self-reported experimentation and problems with drug use. This relationship remained significant even after controlling for preexisting psychosocial factors. In Study 2, perceptions of these "risks-in-the-benefits" were shown (a) to be distinct from perceptions of immediate benefits and (b) to serve as a protective factor against future alcohol use. Results are discussed in terms of creating improved interventions.

US women's attitudes to false positive mammography results and detection of ductal carcinoma in situ: cross sectional survey.

OBJECTIVE: To determine women's attitudes to and knowledge of both false positive mammography results and the detection of ductal carcinoma in situ after screening mammography. DESIGN: Cross sectional survey. SETTING: United States. PARTICIPANTS: 479 women aged 18-97 years who did not report a history of breast cancer. MAIN OUTCOME MEASURES: Attitudes to and knowledge of false positive results and the detection of ductal carcinoma in situ after screening mammography. RESULTS: Women were aware that false positive results do occur. Their median estimate of the false positive rate for 10 years of annual screening was 20% (25th percentile estimate, 10%; 75th percentile estimate, 45%). The women were highly tolerant of false positives: 63% thought that 500 or more false positives per life saved was reasonable and 37% would tolerate 10 000 or more. Women who had had a false positive result (n=76) expressed the same high tolerance: 39% would tolerate 10 000 or more false positives. 62% of women did not want to take false positive results into account when deciding about screening. Only 8% of women thought that mammography could harm a woman without breast cancer, and 94% doubted the possibility of non-progressive breast cancers. Few had heard about ductal carcinoma in situ, a cancer that may not progress, but when informed, 60% of women wanted to take into account the possibility of it being detected when deciding about screening. CONCLUSIONS: Women are aware of false positives and seem to view them as an acceptable consequence of screening mammography. In contrast, most women are unaware that screening can detect cancers that may never progress but feel that such information would be relevant. Education should perhaps focus less on false positives and more on the less familiar outcome of detection of ductal carcinoma in situ.

Women's understanding of the mammography screening debate.

BACKGROUND: The fractious public debate over mammography screening recommendations for women aged 40 to 49 years has received extensive attention in medical journals and in the press. OBJECTIVE: To learn how women interpret the mammography screening debate. METHODS: We mailed a survey to a random sample of American women 18 years and older, oversampling women of screening age (40-70 years). Sixty-six percent of women completed the survey (n = 503). MAIN OUTCOME MEASURES: The main outcome measures were women's reactions to the debate, their suggestion for the starting age for mammography screening, and their understanding of the source of the debate. RESULTS: Almost all women (95%) said that they had paid some attention to the recent discussion about mammography screening. Only 24% said the discussion had improved their understanding of mammography, while 50% reported being upset by the public disagreement among screening experts. Women's beliefs about mammography differed from those articulated by experts in the debate. Eighty-three percent believed that mammography had proven benefit for women aged 40 to 49 years, and 38% believed that benefit was proven for women younger than 40 years. Most women suggested that mammography screening should begin before age 40 years, while only 5% suggested a first mammogram should be performed at 50 years or older. In response to an open-ended question about why mammography has been controversial, 15% cited concerns about the potential harms of radiation and another 12% cited questions about efficacy. Nearly half (49%), however, identified costs as the major source of debate (eg, "Health maintenance organizations [HMOs] don't want to pay for mammography"). CONCLUSIONS: Most women paid attention to the recent debate about routine mammography screening for women aged 40 to 49 years, but many believed the debate was about money rather than the question of benefit. Policy makers issuing recommendations about implementation of large-scale mammography screening services need to consider how to effectively disseminate their message.

Verbal and Numerical Expressions of Probability: "It's a Fifty-Fifty Chance"

When estimating risks, people may use "50" as an expression of the verbal phrase "fifty-fifty chance," without intending the associated number of 50%. The result is an excess of 50s in the response distribution. The present study examined factors determining the magnitude of such a "50 blip," using a large sample of adolescents and adults. We found that phrasing probability questions in a distributional format (asking about risks as a percentage in a population) rather than in a singular format (asking about risks to an individual) reduced the use of "50." Less numerate respondents, children, and less educated adults were more likely to say "50." Finally, events that evoked feelings of less perceived control led to more 50s. The results are discussed in terms of what they reveal about how people express epistemic uncertainty. Copyright 2000 Academic Press.