Wheeler et al. BMC Cancer 2011, 11:148 http://www.biomedcentral.com/1471-2407/11/148 patient knowledge about PSA testing and prostate cancer, as 48% of respondents failed to answer correctly any one of three knowledge questions about prostate cancer screening [23]. Health care providers may not emphasize in a discussion all the information that patients might consider important [29], and they may also present infor- mation in an unbalanced way. In one study, the health care provider more often emphasized benefits of PSA screening (71%) than its harms (32%) [23]. Another sur- vey found that physicians placed less value on providing information to patients than did patients [30]. Physicians may also overestimate the level of patient knowledge about the disease and treatment options [29]. As a result, patients may not get all the information they need from their physician to make a decision. SDM and IDM approaches are only fully effective when patients are truly well informed [31,32]. The increasing use of decision aids should help to educate patients about the risks and bene- fits of screening and also alleviate the time burden on clinicians and increase the utilization of IDM. While IDM/SDM approaches are promising for allowing a patient to make a decision that is concordant with their values and preferences, barriers to rational thought could influence the preferences expressed by patients. Tradi- tional economic decision-making models assume that individuals are consistent, rational decision-makers. How- ever, evidence from studies in psychology and behavioural economics shows that individuals are often not good judges of what would improve their well-being, and they frequently make uninformed or suboptimal choices regarding their own welfare [25-27,33]. Individuals are subject to an assortment of biases (e.g. discounting, omis- sion, status quo, loss aversion [25,26,34,35]), and emotion (e.g., fear, anxiety), which can generate irrational thoughts that interfere with making informed choices. Status quo bias will lead a patient to adhere to the path of least resis- tance even if a superior option exists [34]. Status quo bias can also be described as a tendency for inertia and going along with the default option. Omission bias entails the preference for a more harmful act of omission (not taking action) over a less harmful act of commission (taking action) [25]. If a patient’s health care provider always recommends PSA testing and portrays it as an automatic course of action, then status quo bias or omission can lead them to follow this course of action even if it is not in the patient’s best interest. The idea of discounting future harms such as incontinence or impotency for the current benefit of peace of mind from a low PSA value can explain a decision for an immediate PSA test. A strong emotional fear of cancer and the desire for an urgent peace of mind can lead to a rash decision about screening when it is pre- sented as an immediate option. Patients may also have dif- ficulty assessing probabilities, and as a result are often overly optimistic about their own outcome when faced Page 3 of 7 with the probabilities of survival with treatment options [36] and overestimate their risk of disease. For example, it has been reported that some men overestimate their life- time risk of developing and dying from prostate cancer [37]. In summary, considering the current challenges to decision making on PSA screening, there are opportu- nities to apply new strategies to the existing decision- making process. Given the widespread promotion of PSA screening through the media [28,31], by some health- related organizations and providers, and through social networks [38], the general enthusiasm for screening in the United States [39], personal fears and overestimation of one’s own longevity [40], and the individual and sys- tem-wide factors influencing health care providers, patients are more likely to undergo PSA testing than not, resulting in unnecessary treatment and harms. Libertarian paternalist strategies for PSA screening Libertarian paternalism is a philosophy that uses the insights of behavioural economics to help people better make better choices [26]. A libertarian paternalistic plan is aware of the biases that may hinder a rational decision by individuals and leads to the design of the choice architec- ture to overcome some of these biases [33]. Major distin- guishing features of libertarian paternalism that are relevant for PSA screening decision making include a default decision rule, the framing of the information influ- encing the decision, and the timing of the decision. Strate- gies based on these aspects of LP can be applied to the IDM/SDM approaches to improve decision making about PSA screening. Default decision In an LP plan or program, there is a default decision rule. The rule states the default option or decision, which is the decision automatically made if an individual does not opt to make a decision of their own. As example, a default rule could be that every eligible person is automatically entered into a program (plan A), or conversely, that eligi- ble persons must elect to enter the program on their own (plan B). In an LP-based approach, an individual is free to go against the default setting by making his or her own decision. If an individual goes against the default when it is an automatic enrolment (plan A), they opt-out of the program. Conversely, if the individual decides against the default when it is an optional enrolment (plan B), they opt-in to the program. In other words, deciding against a default option of no required action for participation is called opt-out, whereas going against inertia to participate is called opt-in. Therefore, the default decision rule in plan A corresponds to an opt-out strategy and the rule in plan B corresponds to an opt-in strategy. Cleary, what is con- sidered as an opt-in or opt-out strategy depends on the default option.