Measured enthusiasm: does the method of reporting trial results alter perceptions of therapeutic effectiveness? Adjuvant chemotherapy for breast cancer: how presentation of recurrence risk influences decision-making. Completeness of reporting trial results: effect on physicians' willingness to prescribe. Teaching Bayesian reasoning: an evaluation of a classroom tutorial for medical students. Health professionals' and service users' interpretation of screening test results: experimental study. Teaching Bayesian reasoning in less than two hours. Influence of method of reporting study results on decision of physicians to prescribe drugs to lower cholesterol concentration. Danish GPs' perception of disease risk and benefit of prevention. Impact of presentation of research results on likelihood of prescribing medications to patients with left ventricular dysfunction. Patients' responses to risk information about the benefits of treating hypertension. Communicating the benefits of chronic preventive therapy: does the format of efficacy data determine patients' acceptance of treatment? Absolutely relative: how research results are summarized can affect treatment decisions. Reconciling population benefits and women's individual autonomy in mammographic screening: in-depth interviews to explore women's views about 'informed choice'. GPs' and physicians' interpretation of risks, benefits and diagnostic test results. [Methods of reporting research-results and their influence on decision-making by cardiologists prescribing drugs for primary and secondary prevention]. Evidence based practice in population health: a regional survey to inform workforce development and organisational change. Does the frame affect the picture? A study into how attitudes to screening for cancer are affected by the way benefits are expressed. The psychology of good judgment: frequency formats and simple algorithms. A randomized comparison of patients' understanding of number needed to treat and other common risk reduction formats. The effect of alternative summary statistics for communicating risk reduction on decisions about taking statins: a randomized trial. How should the impact of different presentations of treatment effects on patient choice be evaluated? A pilot randomized trial. The framing effect of relative and absolute risk. Effects of information framing on the intentions of family physicians to prescribe long-term hormone replacement therapy. The role of numeracy in understanding the benefit of screening mammography. Perception of risk information. Similarities and differences between Danish and Polish general practitioners. Evidence based purchasing: understanding results of clinical trials and systematic reviews. Influence of 'framing effect' on women's support for government funding of breast cancer screening. Same information, different decisions: the influence of evidence on the management of hypertension in the elderly.
To compare clinicians' ratings of therapeutic effectiveness when different trial end points were presented as percent reductions in relative compared with absolute risk and as numbers of patients treated to avoid one adverse outcome.
                Survey, with random allocation of two questionnaires.
                Toronto teaching hospitals.
                Convenience sample of 100 faculty and housestaff in internal medicine and family medicine.
                One questionnaire presented results for three end points of the Helsinki Heart Study as separate drug trials using only absolute differences in events; the other showed the same end points as relative differences. Both questionnaires included a fourth "trial," showing person-years of treatment needed to prevent one myocardial infarction.
                The "trials" were each rated on an 11-point scale, from treatment "harmful" to "very effective."
                Respondents' ratings of effectiveness varied with the end point. Controlling for end point, ratings of effectiveness by the 50 participants receiving absolute event data were lower than those by 50 participants responding to relative risk reductions (P < 0.001); however, no end-point difference was more than 0.6 scale points. For a "trial" reporting that 77 persons were treated for 5 years to prevent one myocardial infarction, mean ratings were 2.3 or 1.8 scale points lower, respectively (both P < 0.001), than when the same data were shown as relative or absolute risk reductions.
                Clinicians' views of drug therapies are affected by the common use of relative risk reductions in both trial reports and advertisements, by end-point emphasis, and, above all, by underuse of summary measures that relate treatment burden to therapeutic yields in a clinically relevant manner. The purpose of this study was to examine the impact of four methods of communicating survival benefits on chemotherapy decisions. We hypothesized that the four methods of communicating mathematically equivalent risk information would lead to different chemotherapy decisions.
                Each participant received two hypothetical scenarios regarding their mother (a postmenopausal woman with an invasive, lymph node-negative, hormone receptor-positive breast cancer) and was asked to decide whether they would encourage their mother to take chemotherapy in addition to surgery and tamoxifen. In the part 1, participants received one of four methods of describing the chemotherapy survival benefit: (1) relative risk reduction, (2) absolute risk reduction, (3) absolute survival benefit, or (4) number needed to treat. In part 2, each participant received all four methods. Following each decision, participants were asked to rate their confidence and confusion regarding their decision.
                Participants included 203 preclinical medical students. In part 1, participants who received relative risk reduction information were significantly more likely to endorse chemotherapy. In part 2, there were no treatment decision differences when participants received all four methods of communicating survival benefits of chemotherapy. However, receiving all four methods led to significantly higher ratings of confusion. In deciding on endorsing chemotherapy, participants understood the information best when presented with data in the absolute survival benefit format.
                These results support the hypothesis that the method used to present information about chemotherapy influences treatment decisions. Absolute survival benefit is the most easily understood method of conveying the information regarding benefit of treatment. Clinical trials may lead to conflicting results. We studied how different ways of reporting results affected physicians' recommendations. A questionnaire distributed to 148 general practitioners presented results of a clinical trial where a reduction of cardiac events and an increase of mortality was reported. Results were shown in four different ways--relative risk reduction, absolute risk reduction, percentages of event-free patients, number needing to be treated to prevent an event--as if they derived from different trials. A fifth presentation was the reduced rate of cardiac events along with the increased rate of mortality. Physicians were asked to estimate how much they would be willing to prescribe each drug. The mean agreement of physicians' decisions was 77 (28)% for relative risk reduction, 24 (28)% for absolute risk reduction, 37 (37)% for different percentages event-free patients, 34 (34)% for number need to treat, and 23 (28)% for events reduction and mortality for increase (p < 0.001 relative risk vs others). The method of reporting trial results and the completeness of information in the case of controversial results affects physicians willingness to prescribe. How likely is a diagnosis, given a particular medical test result? This probability can be determined by using Bayes's rule; however, previous research has shown that doctors often experience problems with Bayesian inferences. These findings illustrate the need to teach statistical reasoning in medical education. A new method of teaching Bayesian reasoning is representation learning: the key idea is to instruct medical students how to translate probability information into a representation that is easier to process, namely natural frequencies. This approach was implemented in a one-hour classroom tutorial to evaluate its effectiveness in this setting and compared with a traditional rule-learning approach. Evaluation took place two months after training by testing students' ability to correctly solve a Bayesian inference task with information represented as probabilities. While both approaches improved performance, almost three times as many students were able to profit from representation training as opposed to rule training. To investigate the accuracy of interpretation of probabilistic screening information by different stakeholder groups and whether presentation as frequencies improves accuracy.
                Between participants experimental design; participants responded to screening information embedded in a scenario.
                Regional maternity service and national conferences and training days.
                43 pregnant women attending their first antenatal appointment in a regional maternity service; 40 companions accompanying the women to their appointments; 42 midwives; 41 obstetricians. Participation rates were 56%, 48%, 89%, and 71% respectively.
                Participants estimated the probability that a positive screening test result meant that a baby actually had Down's syndrome on the basis of all the relevant information, which was presented in a scenario. They were randomly assigned to scenarios that presented the information in percentage (n = 86) or frequency (n = 83) format. They also gave basic demographic information and rated their confidence in their estimate.
                Most responses (86%) were incorrect. Obstetricians gave significantly more correct answers (although still only 34% [corrected]) than either midwives (0%) or pregnant women (9%). Overall, the proportion of correct answers was higher for presentation as frequencies (24%) than for presentation as percentages (6%), but further analysis showed that this difference occurred only in responses from obstetricians. Many health professionals were confident in their incorrect responses.
                Most stakeholders in pregnancy screening draw incorrect inferences from probabilistic information, and health professionals need to be aware of the difficulties that both they and their patients have with such information. Moreover, they should be aware that different people make different mistakes and that ways of conveying information that help some people will not help others. The authors present and test a new method of teaching Bayesian reasoning, something about which previous teaching studies reported little success. Based on G. Gigerenzer and U. Hoffrage's (1995) ecological framework, the authors wrote a computerized tutorial program to train people to construct frequency representations (representation training) rather than to insert probabilities into Bayes's rule (rule training). Bayesian computations are simpler to perform with natural frequencies than with probabilities, and there are evolutionary reasons for assuming that cognitive algorithms have been developed to deal with natural frequencies. In 2 studies, the authors compared representation training with rule training; the criteria were an immediate learning effect, transfer to new problems, and long-term temporal stability. Rule training was as good in transfer as representation training, but representation training had a higher immediate learning effect and greater temporal stability. To determine whether the reporting of study results by using reductions in relative or absolute risk and the number needed to treat affects the views of physicians about the effectiveness of drugs to lower lipid concentrations and decisions about treatment.
                Random allocation of two questionnaires presenting the results of three end points of the Helsinki heart study as results from separate trials by using reduction in either relative or absolute risk. In both questionnaires one end point was also presented by showing person years of treatment needed to prevent one myocardial infarction. The effectiveness of lipid lowering drugs was assessed for all end points on an 11 point scale. For each study result the likelihood to treat hypercholesterolaemia of 7.5 mmol/l in a healthy man had to be indicated on a seven point scale.
                Random sample of 802 internists and general practitioners representative of providers of primary care in Switzerland.
                The response rate was 69.6% (558). For the prevention of fatal and non-fatal myocardial infarction the mean ratings of effectiveness of lipid lowering drugs were 0.45 (95% confidence interval 0.21 to 0.69) and 1.39 (1.09 to 1.68) scale points lower when the reduction of absolute risk or number needed to treat were reported instead of the relative risk reduction (both P < 0.001). Physicians receiving trial results for identical end points in form of absolute reduction of risk or number needed to treat were less inclined to treat hypercholesterolaemia (both P < 0.001).
                Physicians' views of the effectiveness of lipid lowering drugs and the decision to prescribe such drugs is affected by the predominant use of reduction of relative risk in trial reports and advertisements. Uncertainty and risk are central issues in relation to health and health care services. Healthy individuals do not necessarily fall ill, despite the presence of risk factors. It has been documented that doctors, health service administrators and patients are more inclined to choose interventions against risk factors when information about the effects is presented in terms of relative risk reductions rather than absolute risk reductions.
                The objective of the study was to gain better insight into how GPs perceive risk of disease, and how this perception is influenced by the way the risk is presented, e.g. whether changes in risk are presented in absolute or relative terms.
                Questionnaires with clinical episodes were sent to 1500 Danish GPs. The GPs were randomized into four groups of 375, who all received the same case story with information about risk reduction achieved through medical treatment phrased in terms of either relative risk reduction, absolute risk reduction, number needed to treat or all of the aforementioned terms of risk reduction. The GPs were asked whether they would recommend medical treatment as primary prevention, knowing the case story and expected risk reduction.
                The GPs' attitude towards recommending medical treatment was dependent on the phrasing of risk reductions. Seventy-two per cent of doctors who received all information on risk reductions would definitely or probably recommend medication, while 91% would recommend medication if information only about relative risk reduction was given, and 63% would recommend medication if information was given in terms of absolute risk reduction or number needed to treat.
                In order to advise patients in a rational way, in addition to knowledge of the patients' preferences, doctors need to take into account all available measures of risk reductions. This study was conducted to evaluate willingness to prescribe medication based on identical data presented in different outcome terms to health professionals of varied discipline, geographic location, and level of training. Cross-sectional survey using a self-administered questionnaire was performed in 400 health professionals (physicians, pharmacists, physicians-in-training, and pharmacy students) in the United States and Europe. Data reflecting a clinical trial were presented in 6 outcome terms: 3 terms describing identical mortality (relative risk reduction, absolute risk reduction, and number of patients needed to be treated to prevent 1 death); and 3 distractors (increased life expectancy, decreased hospitalization rate, and decreased cost). Willingness to prescribe and rank order of medication preference assuming willingness to prescribe were measured. The results of the study showed that willingness to prescribe and first choice preference were significantly greater when study results were presented as relative risk reduction than when identical mortality data were presented as absolute risk reduction or number of patients needed to be treated to avoid 1 death (p <0.001). Increase in life expectancy was the most influential distractor. In conclusion, this study, performed in the era of "evidence-based medicine," demonstrates that the method of reporting research trial results has significant influence on health professionals' willingness to prescribe. The high numerical value of relative risk reduction and the concrete and tangible quality of increased life expectancy exert greater influence on health professionals than other standard outcome terms. The medical profession is often presented with information on the value of treatment in terms of likely risk reduction. If this same information was presented to patients--so enabling them to give proper informed consent--would this affect their decision to be treated?
                To examine patients' choice about treatment in response to different forms of risk presentation.
                Postal questionnaire study.
                The questionnaire was sent to 102 hypertensive patients and 207 matched non-hypertensive patients aged between 35 and 65 years in a UK general practice.
                Patients were asked the likelihood, on a four-point scale, of their accepting treatment for a chronic condition (mild hypertension) on the basis of relative risk reduction, absolute risk reduction, number needed to treat, and personal probability of benefit.
                An 89% response rate was obtained. Of these, 92% would accept treatment using a relative risk reduction model, 75% would accept treatment using an absolute risk reduction model, 68% would accept treatment using a number needed to treat model, and 44% would accept treatment with a personal probability of benefit model.
                Many patients may prefer not to take treatment for mild hypertension if the risks were fully explained. However, given that the form of the explanation has a strong influence on the patient's decision, it is not clear how decision-making can be fully shared nor what should constitute informed consent to treatment in this situation. Patients' informed acceptance of chronic medical therapy hinges on communicating the potential benefits of drugs in quantitative terms. In a hypothetical scenario of treatment initiation, the authors assessed how three different formats of the same data affected the willingness of 100 outpatients to take what were implied to be three different lipid-lowering drugs. Side-effects were declared negligible and costs insured. Subjects make a "yes-no" decision about taking such a medication, and graded the decision on a certainty scale. Advised of a relative risk reduction--"34% reduction in heart attacks"--88% of the patients assented to therapy. All other formats elicited significantly more refusals (p < 0.0001): for absolute risk difference--"1.4% fewer patients had heart attacks"--42% assented; for inverted absolute risk--"treat 71 persons for 5 years to prevent one heart attack"--only 31% accepted treatment. When the data were extrapolated to disease-free survival--"average gain of 15 weeks"--40% consented. Similar responses were obtained for descriptions of an antihypertensive drug: 89% assented to therapy when given relative risk reduction but only 46% when given absolute risk reduction. The subjects were confident in both acceptance and refusal: 93% of the decisions were rated "somewhat certain" to "completely certain." The authors conclude that patients' views of medical therapy are shaped by the formats in which potential benefits are presented. Multiple complementary formats may be most appropriate. The results imply that many patients may decline treatment if briefed on the likelihood or extent of benefit. To determine whether alternative methods of presenting a contrast between the same two quantities in descriptions of research results could lead to different treatment decisions by physicians.
                We conducted a survey of practicing physicians and of faculty and fellows in training programs in clinical epidemiology and social science research methods. Each questionnaire presented results from a published study of either hypertension or hypercholesterolemia in two different ways: once as the relative change in the outcome rate and once as the absolute change in the outcome rate. We asked respondents to read each summary and indicate how the information contained in the summary would influence decisions about treatment.
                Of the 235 physicians who completed the questionnaire, 108 (46%) gave different responses to the same results presented in different ways. Of these, 97 (89.8%) indicated a stronger inclination to treat patients after reading of the relative change in the outcome rate (p less than 0.0001).
                The manner of presentation of results can influence physicians' judgments about the treatment of patients. To explore women's reactions to 'informed choice' in mammographic screening.
                Telephone interviews with a convenience sample of 106 women aged 45-70 years recruited from general practices in Sydney.
                Many (42%) women preferred an active role in decision-making. Respondents had low scores for 'uncertainty' and 'factors contributing to uncertainty' in response to explicit questions about the decision to have mammographic screening. Yet respondents indicated significantly greater willingness to have a test when the benefit of a 'new' screening test for breast cancer was expressed as relative risk reduction (RRR) (88%) than either absolute risk reduction (ARR) (78%) (McNemar's test: chi(2)1=7.14, p=0.013) or all-cause mortality (53%) (McNemar's test: chi(2)1=35.1, p<0.01). Significantly more respondents considered information about ARR 'new' to them (65%) compared with RRR information (30%) (McNemar's test: chi(2)1=25.83, p<0.01).
                As mammographic screening exposes well women to potential harms for an overall population benefit, it is challenging to ensure 'informed choice'. Our results suggest women will likely appreciate individual consultations as the context in which to share complex information that women in our study agreed they need to know about mammographic screening. Our results also demonstrate that women's willingness as individuals to participate in mammographic screening is influenced by 'framing effect'. Hence, the quantitative content of decision aids to promote 'informed choice' must be comprehensive and balanced. Understanding pre-test probability and baseline risks helps to interpret the results of diagnostic tests and the benefits of treatment, but how good is the understanding of these concepts?
                Our aim was to assess the ability of GPs and consultant physicians to make accurate estimates and understand the application of pre-test probability and baseline risk for two common clinical conditions.
                A two-stage questionnaire survey based on case scenarios of patients with angina and congestive heart failure was carried out of 202 physicians, randomly selected from the members of the Royal College of Physicians in the NW of England, 205 GPs randomly chosen from the practice list of the NW Health Authorities and 128 MRCGP examiners attending an examiners meeting. A total of 115, 106 and 81 members of these groups, respectively, responded to the first stage, and 44, 46 and 64 to the second. The main outcome measures were the stated likelihood of true ischaemic heart disease (IHD) being present and the predicted 1-year mortality; the impact of changing prevalence and baseline risk on these results; and interpretation of different methods of risk presentation.
                Estimates of pre-test probability of IHD being present ranged from 5 to 100% and of baseline risk of 1-year mortality from 0 to 86%. More GP examiners and consultant physicians understood the impact of increasing age on the test result than did the random sample of GPs. A majority of each group correctly said that increasing age would reduce the number needed to treat (NNT). Presentation of benefit as relative risk reduction was a greater stimulus to starting treatment than the NNT or measures of population impact.
                Clinicians should collect data to allow a better knowledge of the likelihood of disease and of baseline risk in their patient populations. Methods to increase the understanding of the influence of pre-test probability on diagnostic test results and of how to quantify and demonstrate the impact of the benefit of interventions should be explored. To assess the influence of the form of presentation of the results of clinical trials on the quantitative perceptions of cardiologists regarding the efficacy of drugs for the primary and secondary prevention of coronary heart disease and their likelihood of prescribing them.
                We conducted a survey of 1,408 cardiologists in Spain who were randomly allocated of three questionnaires that used different measurements to evaluate the impact of published clinical trials.
                Five-hundred and fifty-nine questionnaires (40%) were suitable for analysis. On a scale of 0 to 10, the following mean efficacy estimates were obtained from questionnaire items that focused, respectively, on the results of clinical trials in terms of relative risk reduction, absolute risk reduction, and number needed to treat: primary prevention with statins: 6.79, 6.38 and 5.43; primary prevention with aspirin: 6.84, 5.06 and 4.25; secondary prevention with statins: 8.16, 7.76 and 7.54; secondary prevention with ACE inhibitors: 7.11, 7.81 and 7.19, and secondary prevention with beta-blockers: 7.22, 7.43 and 6.98. The likelihood that a drug treatment would be prescribed was not influenced very much by the form of presentation of the trial results.
                Presenting the results of clinical trials in the form of relative risk reduction, as compared with presenting results in terms of absolute risk reduction or number needed to treat, led to overestimation of the efficacy of interventions without influencing the likelihood of prescribing a given drug therapy. To assess current capacity to implement evidence based practice (EBP) in population health.
                Postal survey of a regional population health workforce in Sydney, Australia.
                Division of Population Health, South Western Sydney Area Health Service.
                104 population health staff (response rate: 73%).
                In the sample of regional population health practitioners, views about the current promotion of EBP were positive. Non-medical respondents with less that Masters degree were more likely to report "high self assessed need" to increase their capacity in EBP (p = 0.022). Confidence in understanding of EBP terminology was not associated with seniority but with highest level of education reached (p<0.000) and having medical qualifications (p<0.000). Occupational category was not associated with respondents' self assessed "need for evidence", "need for EBP skills" or "need to increase their capacity in EBP" in their current position. The proportion of participants "strongly" supporting implementation of a colorectal cancer screening programme whose benefit was expressed as relative risk reduction was greater than that so supporting a programme whose benefit was expressed as number needed to screen (p = 0.008). Most respondents referred to their immediate managers when seeking support for EBP.
                The findings provide a quantitative baseline for capacity building through workplace programmes. Managerial commitment has been increased and performance development is now underway. To find out how presenting information about the benefits of screening for cancer in different ways affects an individual's decision to accept or reject screening.
                A telephone survey of the Wellington region, New Zealand was carried out.
                A response rate of 75.6% was obtained. Respondents were most likely to accept screening when the benefits of screening were presented as a relative risk reduction. They were most likely to reject screening when the benefits were presented as numbers needed to screen to save on life.
                An individual's decision about screening for cancer is affected by the way the benefits are framed. Health professionals must choose between framing the benefits of screening in the most positive light, to enhance participation rates, and presenting information in such a way as to reduce framing effects--for example, by expressing the benefits in a variety of forms. Clearly there may be a tension between these approaches; the former is arguably manipulation, and the latter may enhance informed choice, but may also reduce participation rates in screening programmes. Mind and environment evolve in tandem--almost a platitude. Much of judgment and decision making research, however, has compared cognition to standard statistical models, rather than to how well it is adapted to its environment. The author argues two points. First, cognitive algorithms are tuned to certain information formats, most likely to those that humans have encountered during their evolutionary history. In particular, Bayesian computations are simpler when the information is in a frequency format than when it is in a probability format. The author investigates whether frequency formats can make physicians reason more often the Bayesian way. Second cognitive algorithms need to operate under constraints of limited time, knowledge, and computational power, and they need to exploit the structures of their environments. The author describes a fast and frugal algorithm. Take The Best, that violates standard principles of rational inference but can be as accurate as sophisticated "optimal" models for diagnostic inference. Commentators have suggested that patients may understand quantitative information about treatment benefits better when they are presented as numbers needed to treat (NNT) rather than as absolute or relative risk reductions.
                To determine whether NNT helps patients interpret treatment benefits better than absolute risk reduction (ARR), relative risk reduction (RRR), or a combination of all three of these risk reduction presentations (COMBO).
                Randomized cross-sectional survey.
                University internal medicine clinic.
                Three hundred fifty-seven men and women, ages 50 to 80, who presented for health care.
                Subjects were given written information about the baseline risk of a hypothetical "disease Y" and were asked (1) to compare the benefits of two drug treatments for disease Y, stating which provided more benefit; and (2) to calculate the effect of one of those drug treatments on a given baseline risk of disease. Risk information was presented to each subject in one of four randomly allocated risk formats: NNT, ARR, RRR, or COMBO.
                When asked to state which of two treatments provided more benefit, subjects who received the RRR format responded correctly most often (60% correct vs 43% for COMBO, 42% for ARR, and 30% for NNT, P =.001). Most subjects were unable to calculate the effect of drug treatment on the given baseline risk of disease, although subjects receiving the RRR and ARR formats responded correctly more often (21% and 17% compared to 7% for COMBO and 6% for NNT, P =.004).
                Patients are best able to interpret the benefits of treatment when they are presented in an RRR format with a given baseline risk of disease. ARR also is easily interpreted. NNT is often misinterpreted by patients and should not be used alone to communicate risk to patients. While different ways of presenting treatment effects can affect health care decisions, little is known about which presentations best help people make decisions consistent with their own values. We compared six summary statistics for communicating coronary heart disease (CHD) risk reduction with statins: relative risk reduction and five absolute summary measures-absolute risk reduction, number needed to treat, event rates, tablets needed to take, and natural frequencies.
                We conducted a randomized trial to determine which presentation resulted in choices most consistent with participants' values. We recruited adult volunteers who participated through an interactive Web site. Participants rated the relative importance of outcomes using visual analogue scales (VAS). We then randomized participants to one of the six summary statistics and asked them to choose whether to take statins based on this information. We calculated a relative importance score (RIS) by subtracting the VAS scores for the downsides of taking statins from the VAS score for CHD. We used logistic regression to determine the association between participants' RIS and their choice. 2,978 participants completed the study. Relative risk reduction resulted in a 21% higher probability of choosing to take statins over all values of RIS compared to the absolute summary statistics. This corresponds to a number needed to treat (NNT) of 5; i.e., for every five participants shown the relative risk reduction one additional participant chose to take statins, compared to the other summary statistics. There were no significant differences among the absolute summary statistics in the association between RIS and participants' decisions whether to take statins. Natural frequencies were best understood (86% reported they understood them well or very well), and participants were most satisfied with this information.
                Presenting the benefits of taking statins as a relative risk reduction increases the likelihood of people accepting treatment compared to presenting absolute summary statistics, independent of the relative importance they attach to the consequences. Natural frequencies may be the most suitable summary statistic for presenting treatment effects, based on self-reported preference, understanding of and satisfaction with the information, and confidence in the decision.
                ISRCTN85194921. Different presentations of treatment effects can affect decisions. However, previous studies have not evaluated which presentations best help people make decisions that are consistent with their own values. We undertook a pilot study to compare different methods for doing this.
                We conducted an Internet-based randomized trial comparing summary statistics for communicating the effects of statins on the risk of coronary heart disease (CHD). Participants rated the relative importance of treatment consequences using visual analogue scales (VAS) and category rating scales (CRS) with five response options. We randomized participants to either VAS or CRS first and to one of six summary statistics: relative risk reduction (RRR) and five absolute measures of effect: absolute risk reduction, number needed to treat, event rates, tablets needed to take, and natural frequencies (whole numbers). We used logistic regression to determine the association between participants' elicited values and treatment choices. 770 participants age 18 or over and literate in English completed the study. In all, 13% in the VAS-first group failed to complete their VAS rating, while 9% of the CRS-first group failed to complete their scoring (p = 0.03). Different ways of weighting the elicited values had little impact on the analyses comparing the different presentations. Most (51%) preferred the RRR compared to the other five summary statistics (1% to 25%, p = 0.074). However, decisions in the group presented the RRR deviated substantially from those made in the other five groups. The odds of participants in the RRR group deciding to take statins were 3.1 to 5.8 times that of those in the other groups across a wide range of values (p = 0.0007). Participants with a scientific background, who were more numerate or had more years of education were more likely to decide not to take statins.
                Internet-based trials comparing different presentations of treatment effects are feasible, but recruiting participants is a major challenge. Despite a slightly higher response rate for CRS, VAS is preferable to avoid approximation of a continuous variable. Although most participants preferred the RRR, participants shown the RRR were more likely to decide to take statins regardless of their values compared with participants who were shown any of the five other summary statistics.
                Controlled-Trials.com ISRCTN85194921. To test whether a patient's perception of benefit is influenced by whether the benefit is presented in relative or absolute terms.
                Questionnaire-based study.
                A general medicine outpatient clinic at a rural tertiary care center associated with a medical school.
                470 of 511 consecutive patients who agreed to answer a questionnaire while waiting for their clinic visit. Mean age was 49.1 years, 62.1% were female, and 51.9% had at least one year of education beyond high school.
                Patient response to the choice of two equally efficacious medications for the management of a hypothetical serious disease. The benefit of one medication was stated in relative terms, the other in absolute terms. Patients could choose either medication alone, indicate indifference to the choice of medication, or choose not to answer.
                56.8% of the patients chose the medication whose benefit was in relative terms. 14.7% chose the medication whose benefit was in absolute terms. Only 15.5% were indifferent to the choice of medication. The patients preferred the medication whose benefit was in relative terms across a wide range of ages and educational levels. Further questioning suggested that the patients thought benefit was greater when expressed in relative terms because they ignored the underlying risk of disease and assumed it was one.
                The "framing" of benefit (or risk) in relative versus absolute terms may have a major influence on patient preference. To determine whether the way in which information on benefits and harms of long-term hormone replacement therapy (HRT) is presented influences family physicians' intentions to prescribe this treatment.
                Family physicians were randomized to receive information on treatment outcomes expressed in relative terms, or as the number needing to be treated (NNT) with HRT to prevent or cause an event. A control group received no information.
                Primary care.
                Family physicians practicing in the Hunter Valley, New South Wales, Australia.
                Estimates of the impact of long-term HRT on risk of coronary events, hip fractures, and breast cancer were summarized as relative (proportional) decreases or increases in risk, or as NNT.
                Intention to prescribe HRT for seven hypothetical patients was measured on Likert scales. Of 389 family physicians working in the Hunter Valley, 243 completed the baseline survey and 215 participated in the randomized trial. Baseline intention to prescribe varied across patients-it was highest in the presence of risk factors for hip fracture, but coexisting risk factors for breast cancer had a strong negative influence. Overall, a larger proportion of subjects receiving information expressed as NNT had reduced intentions, and a smaller proportion had increased intentions to prescribe HRT than those receiving the information expressed in relative terms, or the control group. However, the differences were small and only reached statistical significance for three hypothetical patients. Framing effects were minimal when the hypothetical patient had coexisting risk factors for breast cancer.
                Information framing had some effect on family physicians' intentions to prescribe HRT, but the effects were smaller than those previously reported, and they were modified by the presence of serious potential adverse treatment effects. Quantitative information about risks and benefits may be meaningful only to patients who have some facility with basic probability and numerical concepts, a construct called numeracy.
                To assess the relation between numeracy and the ability to make use of typical risk reduction expressions about the benefit of screening mammography.
                Randomized, cross-sectional survey.
                A simple random sample of 500 female veterans drawn from a New England registry.
                One of four questionnaires, which differed only in how the same information on average risk reduction with mammography was presented.
                Numeracy was scored as the total number of correct responses to three simple tasks. Participants estimated their risk for death from breast cancer with and without mammography. Accuracy was judged as each woman's ability to adjust her perceived risk in accordance with the risk reduction data presented.
                61% of eligible women completed the questionnaire. The median age of these women was 68 years (range, 27 to 88 years), and 96% were high school graduates. Both accuracy in applying risk reduction information and numeracy were poor (one third of respondents thought that 1000 flips of a fair coin would result in < 300 heads). Accuracy was strongly related to numeracy: The accuracy rate was 5.8% (95% CI, 0.8% to 10.7%) for a numeracy score of 0, 8.9% (CI, 2.5% to 15.3%) for a score of 1, 23.7% (CI, 13.9% to 33.5%) for a score of 2, and 40% (CI, 25.1% to 54.9%) for a score of 3.
                Regardless of how information was presented, numeracy was strongly related to accurately gauging the benefit of mammography. More effective formats are needed to communicate quantitative information about risks and benefits. The objective of the study was to gain better insight into how general practitioners (GPs) perceive risk reduction and the way this perception may be influenced by healthcare environment.
                Questionnaires with clinical episodes were sent to Danish and Polish GPs, who were randomised into four groups, each receiving the same case story with differently phrased information about risk reduction achieved through medical treatment. The GPs were asked whether they would recommend medical treatment, knowing the case story and expected risk reduction.
                Danish and Polish GPs.
                A greater proportion of Polish GPs than Danish GPs would definitely or probably recommend treatment (93% versus 72%; p < 0.001). Both groups of doctors were more inclined to recommend treatment when the achievable benefits were presented in terms of relative risk reduction rather than absolute risk reduction or number needed to treat.
                Neither information on number needed to treat nor relative risk reduction alone provides doctors with all the information they need to recommend treatment or prevention to their patients. The present study showed that the professional handling of risk information is affected by differences produced by healthcare cultures. To assess whether the way in which the results of a randomised controlled trial and a systematic review are presented influences health policy decisions.
                A postal questionnaire to all members of a health authority within one regional health authority.
                Anglia and Oxford regional health authorities.
                182 executive and non-executive members of 13 health authorities, family health services authorities, or health commissions.
                The average score from all health authority members in terms of their willingness to fund a mammography programme or cardiac rehabilitation programme according to four different ways of presenting the same results of research evidence--namely, as a relative risk reduction, absolute risk reduction, proportion of event free patients, or as the number of patients needed to be treated to prevent an adverse event.
                The willingness to fund either programme was significantly influenced by the way in which data were presented. Results of both programmes when expressed as relative risk reductions produced significantly higher scores when compared with other methods (P < 0.05). The difference was more extreme for mammography, for which the outcome condition is rarer.
                The method of reporting trial results has a considerable influence on the health policy decisions made by health authority members. To explore whether Australian women's support for government funding of mammographic screening is influenced by 'framing effect'.
                Self-administered survey of 701 women in general practice to elicit their support for government funding of each of four mammographic screening programs where benefits were expressed as a relative risk reduction (RRR); absolute risk reduction (ARR); number needed to screen (NNS) and number of cases detected for additional death avoided.
                The proportion of respondents indicating they 'definitely would support funding' was significantly greater when benefits were expressed as RRR than ARR (chi 2(1) = 148.4, p < 0.0001), NNS (chi 2(1) = 126.4, p < 0.0001) or number of cases detected for additional deaths avoided (chi 2(1) = 29.0, p < 0.0001). 55.8% of women were not influenced by 'framing effect'. Younger women and those with higher educational levels were more likely to be susceptible to 'framing effect'.
                Having demonstrated its influence among these women, 'framing effect' should be acknowledged in future research. Evidence-based medicine requires general practitioners (GPs) to act upon the results of clinical trials. Clinical trial evidence may be difficult to understand and apply in practice.
                To investigate whether GPs were unduly influenced in managing hypertension in the elderly by the ways in which benefits of trial results were presented, and to establish whether their current treatment of an elderly hypertensive patient was broadly in line with recent clinical trial evidence.
                Seventy-three GPs attending a refresher course were given a written questionnaire containing data from one clinical trial of treatment of hypertension in the elderly presented in four different ways (absolute risk reduction, relative risk reduction, difference in event-free patients, and number of patients who had to be treated in order to prevent one clinical event), as if from four different trials. The effect of each presentation on treatment preferences was assessed using Likert scales. The results were analysed to determine whether the method of presentation of results influenced decision making. A clinical scenario was presented to investigate their current treatment preferences in an elderly hypertensive.
                All GPs returned completed questionnaires. Relative risk reduction was the only presentation which was significantly different from the others, and was the most likely to influence prescribing. In free-text comments, 75% of GPs admitted having problems understanding statistics commonly found in medical journals. More than 90% conformed with recent clinical trial evidence for the management of hypertension.
                GPs were most influenced by relative risk reduction, and were unaware of how the presentation of research results could affect treatment decisions. Most GPs freely admitted to difficulty in comprehending medical statistics. Almost all of the GPs expressed treatment decisions which were broadly in line with clinical evidence.
Natural frequencies are probably better understood than percentages in the context of diagnostic or screening tests. For communicating risk reductions, relative risk reduction (RRR), compared with absolute risk reduction (ARR) and number needed to treat (NNT), may be perceived to be larger and is more likely to be persuasive. However, it is uncertain whether presenting RRR is likely to help people make decisions most consistent with their own values and, in fact, it could lead to misinterpretation. More research is needed to further explore this question.