MUMJ Original Research 15 ORIGINAL RESEARCH It s All Relative: How Presentation of Information To Patients Influences Their Decision-Making Mohit Bhandari, MD, MSc Vikas Khera, BSc Jaydeep K. Moro, MD ABSTRACT Background: Risk information is understood differently when it is presented in absolute or relative terms; the latter overemphasizes the magnitude of risk. How surgeons communicate risk may influence patient choice. Purpose: To evaluate whether presenting information about the benefits of surgery in absolute and relative terms affects an individual's decision to accept or reject surgery. Methods: We administered a face-to-face survey to 50 patients attending the fracture clinic at a Universityaffiliated hospital. We asked patients to consider a wrist fracture scenario and to decide whether they would choose surgery or casting. We presented risk in 5 ways: 1) absolute risk difference, 2) relative risk reduction, 3) relative risk, 4) number needed to treat (NNT), and 5) odds ratio. After considering each risk presentation, patients expressed their preference for surgery using a 5-point Likert-type scale. Results: Patients were 21 to 88 years-old, 66% male, and 66% Caucasian; 60% completed high school; 52% had been treated for previous fractures. Patients were most likely to favour surgery when the results comparing surgery versus casting were presented as a relative risk reduction (90%, 95% confidence interval 79-96%) or relative risk (76%, 62-83%) than when presented with an odds ratio (48%, 95% confidence interval 35-62%) or NNT (36%, 95% confidence intervals 24-50%). Conclusions: Our findings show how framing risk in relative terms affects the perception of risk and influences patient choice. Using relative risk reductions to communicate benefit of surgery has the greatest influence on patient s decision to undergo surgery. INTRODUCTION The presentation of information about treatment alternatives to physicians can strongly influence their decision-making and patient care. Previous studies have shown that physicians views are shaped by the presentation style of study results in advertisements and published research papers.1-4 While the goal of physician-patient interactions is to promote health care decisions that are consistent with patients own values and beliefs, it remains unclear how framing treatment options to patients contemplating surgery alters their perceptions about treatment efficacy. Previous reports have addressed these influences,5-7 but the effect of the actual wording used to describe risks of alternative treatments remains unclear. Additionally, investigators have focused upon medical therapies such as cholesterol-lowering interventions, hypertension therapies, and medical interventions for myocardial infarction.5-7 No studies have evaluated the communication of surgical alternatives in patients with previous fractures. In such instances, patients may be faced with the alternative of no surgery versus surgery. The surgeon s approach to presenting relevant information may have even a stronger influence in such settings. Information comparing the outcomes of two procedures may be presented to patients as an odds ratio, a relative risk, a relative risk reduction, an absolute risk reduction, and the number needed to treat.8 Both reduction in relative risk and reduction in absolute risk have been reported to have the strongest influences on patient decision-making in non-sur-
16 Original Research Volume 1 No. 1, 2003 gical therapies.1-8 We hypothesized that patients considering surgery would be equally influenced by relative risk reductions. To test our hypothesis, we conducted face-toface surveys with patients being treated for a variety of musculoskeletal disorders to examine the influence of presentation methods of treatment risk and their endorsement for surgery. Moreover, we aimed to identify any patient factors that were significantly associated with this decision-making process. Understanding the Variables Reduction Number Needed to Treat Risk in the treatment group compared to risk in the control group. (Also known as risk ratio.) The amount by which the risk of an event is reduced by the proposed treatment. Ratio of the odds of having the event in the experimental group relative to the odds of having the event in the control group The number of patients who need to be treated in order to prevent one additional bad outcome. Sackett DL, Straus SE, Richardson WS, et al. (2000). Evidence-Based Medicine: How To Practice And Teach EBM. Churchill Livingstone: Toronto, ON. A Practical Explanation of the Variables Example: % of % of Casting = 20% Patients Patients risk of bone shift Information Favouring Favouring Surgery = 10% presented to Surgery Casting risk of bone shift patients Casting presents a 2 times 76% 24% higher risk of bone shift as compared to surgery Surgery affords a 50% 90% 10% Reduction risk reduction of bone shift as compared with casting The odds of having a bone 48% 52% shift with surgery are 0.44 times that of casting Number Needed For every 10 patients treated 36% 64% to Treat with this surgery, 1 case of bone shift can be prevented METHODS Study Population We approached 100 consecutive patients presenting to a fracture clinic in January 2003 at a University-affiliated hospital. Eligibility for the study included the following: 1) English-speaking; 2) Age > 16 years; 3) Absence of cognitive impairment; and, 4) Informed consent. A single physician interviewer administered the questionnaire to each eligible patient. The interviewer provided only clarifications of the questions and did not provide opinions. Each interviewer-administered questionnaire took approximately 15 minutes to complete. Baseline Data Collection We collected the following baseline information from each patient: 1) age; 2) gender; 3) occupation; 4) highest level of education; 5) ethnicity; 6) type of injury (traumatic, non-traumatic). Questionnaires We developed a single scenario aimed at identifying how patients perceptions about having a surgical procedure versus non-operative treatment changed by the manner in which data was presented. The questionnaire was piloted among three surgeons and five patients to ensure clarity. The hypothetical scenario was as follows: Suppose you slip on winter ice and injure your wrist. After being seen in the emergency department, the orthopaedic surgeon on call tells you that you have broken your wrist. She further states that the type of injury you have can be set with a plaster cast but there is a small risk that the bones may shift. If the bones shift in the cast, you will likely need an operation to re-set the bone and fix it with metal wires. Alternatively, you can have an operation now to reduce the chances of the bones shifting. Remember that having an operation also means that you ll need an anesthetic and could get an infection (small chance) where your surgeon makes the cut. Having received the scenario above, patients were presented comparative data on the proportion of patients with each treatment alternative in which the bones subsequently shifted (loss of fracture reduction). Patients were told, suppose your surgeon tells you the following information about the benefits of surgery and casting, how would you respond? Each patient was then provided with 5 separate hypothetical surgeon responses presented in one of five different ways: absolute risk difference, relative risk reduction, relative risk, number needed to treat and an odds ratio. For instance, patients were told the casting incurred a 20% risk of bone shift and surgery incurred a 10% risk of bone shift. This exact same data was then presented as a relative risk reduction (50% reduction in the risk of bone shift compared with casting), relative risk (casting has two times the risk of bone shift than surgery), number needed to treat (for every ten patients treated with surgery, one case of bone shift can be prevented), and an odds ratio (the odds of having a bone shift with surgery is 0.44 times that of casting). For each presentation method, patients were asked whether
MUMJ Original Research 17 they were in favour of surgery in a five-point Likert-type scale (1 = Strongly favour surgery, 2 = moderately favour surgery, 3 = unsure, 4 = moderately favour casting, 5 = strongly favour casting). Patients were not told that the data being presented in the five separate responses was the same data but presented in a various ways. DATA ANALYSIS All data analysis was conducted with SPSS (Version 11, professional) statistical software. The data forms were entered into the database by VK and re-checked by MB for accuracy. Continuous variables (age) were summarized with means and standard deviations. Categorical variables (gender, level of education) were presented as proportions. For each presentation method, the proportion of patients responses that favored surgery was presented with 95% confidence intervals. Chi-square tests (or Fisher s exact tests) were conducted to compare proportions. We further evaluated whether age, gender, injury type, level of education, occupation, and ethnicity were associated with the presentation type in five separate regression analyses. Briefly, univariable analyses were conducted against the dependent variable (favours surgery from 1-5). Those variables that revealed significance at the p <.05 level were entered into a multivariable model. Statistical significance was considered p <.05. All tests were two tailed. RESULTS Of 100 patients approached, 50 patients met all eligibility criteria. Fifty patients were not included for the following reasons: 10 non-english speaking, 15 cognitively impaired, 14 were aged less than 16 years old, and 10 did not consent to the survey. Non-consenting patients were demographically similar to the included patients (mean age = 44, 50% male, 50% traumatic injury, 60% Caucasians). Patients were predominantly Caucasian (66%), male (66%), with college or university education (60%), and ranging in age from 21-88 years (Table 1). Over half the patients were being treated for previous fractures (52%). Patients were most likely to favour surgery when the results comparing surgery versus casting were presented as a relative risk reduction (90%, 95% confidence interval 79-96%) or relative risk (76%, 95% confidence interval 62-83%) (Figure 1). Significantly lower endorsement was noted for results presented as odds ratios (48%, 95% confidence interval 35-62%), or number needed to treat (36%, 95% confidence intervals 24-50%) (Figure 1). In addition, when information was presented as a number needed to treat patients were most likely to be unsure about the relative merits of surgery compared to casting (44%, 95% confidence interval 31-58%) (Figure 2). Table 1. Baseline Characteristics of the Patients (N=50) Age (Mean, St. Dev, Range) 47.3 ± 17.8 (21-88) % Male (number) 66% (33) Level of Education %Grade school 6% (3) %High school 34% (17) %College 26% (13) %University 34% (17) Type of Injury %Fracture 52% (26) Upper Extremity 22% (11) Lower Extremity 28% (14) Spine 2% (1) %Non-fracture 48% (24) Soft tissue injury 20% (10) Elective surgery 28% (14) Occupation %Laborer 32% (16) %Sedentary 54% (27) %Student 8% (4) %Retired 4% (2) %Unemployed 2% (1) Ethnicity %Caucasian 66% (33) %African-American 2% (1) %South Asian 20% (10) %European 12% (6) St. Dev = standard deviation We explored potential predictors of patients decisions regarding the presentation style. Both injury type (trauma vs no trauma) and level of education were significantly associated with endorsement for surgery (B=0.53, P=0.02 and B=0.31, P=0.05, respectively). Patients with a lower level of education and those who were being treated for non-fracture diagnoses were more likely to be unsure of the relative benefits of surgery (67% and 53%, respectively) compared with those patients with higher levels of education and previous fractures (6% and 12%, respectively). DISCUSSION In a face-to-face survey of 50 patients being treated for musculoskeletal disorders, we report the following: 1) Information presented as relative risk reduction or relative risk is more likely to influence patient perceptions about fracture surgery; and, 2) Level of education and previous fractures in patients are significantly associated with the method of information presentation. This is the first study to evaluate the impact of different strategies to relay information about a surgical procedure to surgical patients. The results are strengthened by application
18 Original Research Volume 1 No. 1, 2003 NNT Reduction Absolute Risk Difference 0 10 20 30 40 50 60 70 80 90 100 % Patients Favouring Surgery Figure 1. Percent of Patients Favouring Surgery Based Upon Presentation Type. Reduction Absolute Risk Difference NNT 0 10 20 30 40 50 60 70 80 90 100 % Patients Unsure Figure 2. Percent of Patients Unsure about Surgery Based Upon Presentation Type. of strict eligibility criteria to consecutive patients, completeness of data collection (100% complete), and exploration of potentially important predictors of patients perceptions regarding information presentation. Our findings may be limited by the smaller sample size with resultant large confidence intervals around the point estimates of effect, and large number of excluded patients. However, the extreme variability in responses noted is unlikely to be eliminated entirely by a larger sample size. A patient's willingness to consent to a procedure may be influenced by a variety of factors, such as the physicianpatient relationship, the way in which the information is conveyed to the patient, and the patient s previous health experiences. As with previous reports, we found that presenting results as a relative risk reduction had the greatest influence on patient perceptions regarding the efficacy of surgery.5-7 Sarfati et al surveyed patients regarding cancer screening. Patients were presented information about the benefits of screening for cancer, using different methods of presenting the data.5 Respondents were most likely to accept the screening when they were presented the information as a relative risk reduction, and they were most likely to reject the screening when presented the information as numbers needed to treat. In addition, Hux and Naylor assessed how different formats of the same data affected the readiness of 100 outpatients to take lipid-lowering drugs.7 When patients were advised of a relative risk reduction, 88% of the patients assented to therapy whereas all other formats obtained significantly more refusals (p<0.0001). Although it may seem logical to use relative risk reductions in communicating information to patients, this method is potentially problematic. In the absence of presenting the baseline risk of an outcome for a procedure, the relative risk reduction may inflate perceptions about the magnitude of the treatment effect. For example a relative risk reduction of 50% may have very different reactions from physicians and patients if the baseline risks are presented as a reduction from 70% to 35% rather than a reduction of 2% to 1%. Thus, it is not at all surprising that patients expressed less favourable perceptions about surgery when presented with absolute risk differences or number needed to treat (reciprocal of the absolute risk difference). This finding is consistent with those of Bucher and colleagues who identified that physicians were likely to have conservative beliefs about treatment effects when presented with number needed to treat data.2 We explored potential reasons why surveyed patients had different perceptions about the efficacy of surgery. Higher levels of education and patients with previous fractures were significantly associated with patients understanding of results presentation. Patients with these characteristics were significantly less likely to answer unsure of the relative benefits of surgery compared to casting. Ethnicity, occupation, age, and gender were not associated with patients beliefs regarding the benefit of surgery. The manner in which results are summarized to patients considering a surgical procedure must be considered carefully to ensure that patients make informed decisions about their own care. While relative risk reductions are most easily understood, they are likely to inflate the perceived
MUMJ Original Research 19 benefits of a surgical procedure. Providing patients with absolute risk differences (or number needed to treat) along with relative risk reduction data may provide important perspective to guide their decisions. AUTHOR BIOGRAPHIES Dr. Bhandari is an orthopaedic surgeon and research fellow with the Department of Clinical Epidemiology and Biostatistics, McMaster University. Vikas Khera is a final year medical student at McMaster University. Jaydeep K. Moro is a consultant orthopaedic surgeon, St. Joseph's Hospital, Division of Orthopaedics, McMaster University. REFERENCES 1. Bucher HC, Weinbacher M, Gyr K. (1994) Influence of method of reporting study results on decision of physicians to prescribe drugs to lower cholesterol concentration. British Medical Journal. 309: 761-764. 2. Forrow L, Taylor WC, Arnold RM. (1992). Absolutely relative: how research results are summarized can affect treatment decisions. American Journal of Medicine. 92: 121-4. 3. Naylor CD, Chen E, Strauss B (1992). Measured enthusiasm: does the method of reporting trial results alter perceptions of therapeutic effectiveness? Annals of Internal Medicine 117: 916-21 4. McGettigan P, Sly K, O Connell D, et al. (1999). The effects of information framing on the practices of physicians. Journal of General Internal Medicine 14: 633-642. 5. Sarfati D, Howden-Chapman P, Woodward A, et al. (1998) Does the frame affect the picture? A study into how attitudes to screening for cancer are affected by the way benefits are expressed. Journal of Medical Screening. 5: 137-140. 6. Gurm HS, and Litaker DG. (2000) Framing Procedural Risks to Patients: Is 99% Safe the Same as a Risk of 1 in 100? Academic Medicine. 75: 540-542. 7. Hux JE and Naylor CD. (1995). Communicating the benefits of chronic preventive therapy: does the format of efficacy data determine patients acceptance of treatment? Medical Decision Making. 15: 152-157. 8. Schechtman E. (2002) Odds ratio, relative risk, absolute risk reduction, and the number needed to treat which of these should we use? Value Health. 5: 430-5.