This study assessed the impact of a computerised decision aid applied in a shared decision‐making consultation on the primary outcome measure of decision conflict as compared to a traditional doctor‐led application of paper guidelines. The key finding was a significantly lower decision conflict in the decision aid group than in the paper‐based guidelines group immediately after the research clinic and this finding was present across all patients regardless of their initial treatment. Decision conflict was lower after the clinic in both groups.
In addition, there was a marked difference between the two arms in the decision whether or not to take warfarin when patients were not already on this treatment; those in the decision aid group were significantly much less likely to start warfarin than those in the paper guidelines arm.
There has been considerable debate about the most appropriate outcome measures for assessing the effectiveness of decision support tools.17
Many studies of guidelines have assessed their effectiveness in terms of adherence to the guidelines' recommendations.18
In the case of shared decision‐making, such a measure is less appropriate, since the aim is to support patients in making a “good decision” in a setting where the choice between treatments is not clear cut and is likely to be sensitive to patient values—that is, to support patients in making informed choices consistent with their values by presenting the clinical evidence and the likely effects of alternative treatments.
The decision conflict scale was developed to measure perceptions of personal uncertainty in making a choice about healthcare options, the modifiable factors contributing to uncertainty, and the quality of the decision made.12,19
Decisional conflict is a state of uncertainty about a course of action and is, for example, more likely when someone is faced with decisions involving risk or uncertainty of outcomes, and when there is a need to make tradeoffs between choices.
Our results show an effect size on decisional conflict that is comparable to other studies of decision aids,19
suggesting that the computerised decision aid does have a measurable and clinically important impact that is greater than the doctor‐led paper‐based guidelines. The difference is not maintained at three months, but this is unsurprising—the measure was designed to assess conflict around the time of a difficult decision. After three months, it is likely that the participants have become comfortable with, and more accepting of, the decision made.
The subscale analysis suggests that the main contributions to the observed difference between groups were from differences in feeling better informed and having greater clarity on values. Although we demonstrated differences in two of the subscales, all subscale scores were lower in the decision aid group. We cannot exclude the possibility of differences in the other three as the study was not powered to show differences in subscale measures.
The noted reduction in anxiety in both groups may be related to the opportunity for a prolonged consultation on their condition. Increased knowledge about warfarin may be related to the additional consultation time and the prior presentation of pre‐clinic information. The effect was more noticeable for warfarin, likely to reflect the fact that in both groups the starting point for discussion was that warfarin is more effective than aspirin in terms of risk reduction,6
and thus the primary discussion was based on whether participants should take warfarin or, if not, consider aspirin.
A prominent finding of the difference in the proportion of participants electing to take warfarin, which is almost fully explained by those not already on warfarin, is worthy of discussion. This implies that the threshold for choosing to take warfarin is higher in those participants using the decision aid. The most likely explanation is that the decision aid used within a shared decision‐making consultation allows for a more balanced presentation of the benefits and the potential harm from warfarin treatment, whereas the paper‐based guidelines, presented as direct advice to the patient, allow less discussion and presentation of potential harm and hence place emphasis on overall effectiveness. Thus participants presented with this balance are less likely to take warfarin given their greater understanding of the potential for harm.
The participants in the study included patients who were not on warfarin as well as patients who were already treated. Both were included because we saw the tool as supporting either initial decision‐making or treatment review (not least because the clinical status of patients changes over time and merits annual review of such decisions as risk profiles may change). We also argued that it was likely that few, if any, of those currently taking warfarin would have had experienced any form of shared decision making, a feature supported by the focus groups and interviews with patients undertaken during the development phase of the decision aid. Nonetheless the decisions being made are different and this may in part explain the differences between decisions on warfarin initiation or continuation demonstrated.
Other studies of decision aids have suggested that participants are less likely to choose the procedure with a greater risk of adverse effects, for example a trial of a decision aid with participants choosing between watchful waiting and more invasive treatments for prostatic symptoms showed a 40% decrease in surgery rates.20
However, overall the systematic review of randomised controlled trials of decision aids does not reveal a consistent impact on treatment choices.4
Studies of risk perception suggest that people are more averse to risks that are out of their control (as may be felt to be the case with adverse effects of treatments) and to be more averse to proximate risks such as early bleed on warfarin, than more distant risks, such as the later risk of stroke.21
It is also the case that the nature of this decision is based on preventing a future event (stroke) that is probabilistic, a different setting to that of making choices between potentially curative treatments such as in cancer therapy. This suggests that application of shared decision‐making, particularly in preventive therapies, might lead to lower rates of uptake of otherwise traditionally defined effective interventions, albeit in participants who are better informed and making decisions consistent with their values. Therefore, although trials may suggest that a patient will, in terms of stroke risk reduction, benefit to a greater extent with warfarin than aspirin, when the patient takes account of their informed personal values they may come to a different decision. This may lead to higher rates of future population health burden in terms of avoidable strokes incurred. There is thus a potential tension between the goals of preventive strategies based upon reduction of population‐level disease burden and the choices made by well‐informed patients.22
A number of studies have assessed decision‐making preferences and treatment thresholds of patients with atrial fibrillation using a range of methods and demonstrate considerable variation in thresholds for warfarin treatment, although few use actual patients making real decisions.23
In studies using decision aids24,25
the majority of patients expressed a preference for aspirin, even if their absolute baseline stroke rate was as high as 4% per year, consistent with the findings of our study. Protheroe and colleagues used a decision analytical approach and found that decisions on treatment based on decision analysis would lead to fewer patients taking warfarin than if the decision were made on the basis of commonly available guidelines.26
Howitt and Armstrong27
found that people already taking warfarin were willing to take it for a lower level of benefit compared with those who were not, again consistent with our differential findings between participants on or not on warfarin at study entry. Furthermore Man‐Son‐Hing et al24
found that most patients already on aspirin preferred to continue taking aspirin rather than switching to warfarin, suggesting a smaller fraction of these patients would take warfarin at most levels of stroke risk compared with those who were taking or had experienced a course of warfarin therapy. Similarly, in the Howitt and Armstrong study,27
many of the patients expressed reluctance to switch from the anti‐thrombotic therapy they were taking to another. Thus it is likely that patients already on an established treatment may prefer to remain with it, and this may in part explain our findings.
Our study has some limitations. The study was designed as an efficacy (explanatory) trial, with the tools being applied in a research clinic setting by appropriately trained doctors. At an early stage, one arm was discontinued (see linked paper8
), but this does not affect the validity of the comparison between the remaining arms, the design of which remained unchanged. It was designed as an explanatory trial and participants were invited to a central clinic to see a doctor who was not primarily responsible for their care. This is an artificial situation, although the high levels of adherence to the decisions made at the clinic at three months suggest that the decisions had real meaning for the participants and their GP.
The fact that we recruited participants to the trial who were largely prevalent cases and already on some form of treatment (aspirin or warfarin), lead to a heterogeneous group of participants and the subgroup differences in decisions made reflect this.
What is already known
- Choice of prevention of stroke with warfarin or aspirin is sensitive to patient preferences.
- Treatment decisions where patient preference is important can be supported by decision aids, but these need evaluation in appropriate studies.
- A systematic review of decision aids shows that they improve patients' knowledge, reduce decision conflict and engage patients more actively in decision‐making, but have little impact on patient satisfaction, and a variable impact on the actual decisions made.
- Some studies show reduction in uptake of procedures or treatments.
What this paper adds
- Participants using a decision aid in a shared decision‐making setting have lower decision conflict after its use than those where paper‐based guidelines are used in a traditional way.
- Those who are not already taking warfarin are much less likely to start this treatment when using the computerised decision aid than in the evidence‐based paper guidelines arm. This could have significant implications for treatment uptake and stroke prevention.
Each clinic was delivered by a single doctor, raising the question as to whether the findings reflect the different interventions, the different doctors delivering the interventions or some combination of the two. In some respects this is a false distinction; we were evaluating a package of decision support, and we attempted to minimise any doctor‐specific effect by training the doctors in the intervention and the desired mode of delivery. The two doctors delivering the clinics did communicate differently, but that was the intention. The decision aid arm of the trial was presented and delivered within a consultation that incorporated a process of shared decision‐making, while the doctor delivering the guidelines advice did so by directly advising the patient on what the guidelines recommended for that patient in a more paternalistic model. Indeed, the results of the survey of participants as to who made the decisions at the clinic suggest that this was effective and hence that the findings are likely to reflect the decision aid and its delivery, rather than the individual characteristics or style of the doctors. There were variations in doctors' behaviours, but these appeared to be related to specific doctor–patient interactions, rather than the arm of the trial. Video‐recording of the interactional dynamics of the consultations and detailed qualitative investigation of patients' perspectives were an important element of this study and have been described in detail elsewhere.28,29
In summary, our study suggests that a computerised decision aid that presents balanced benefits and harms of therapy in the setting of shared decision‐making can lead to reduced decision conflict with an enhanced understanding by patients and decisions consistent with their values. This reflects the findings of use of similar decision aids in other clinical settings. In addition we found a marked difference in the actual decisions made in participants who were not already on warfarin with an apparent reluctance to start warfarin when participants were well informed and able to apply their values to their decisions. This finding may have significant implications for the impact of shared decision‐making and the use of decision aids in patients who are making decisions about preventive therapies and is worthy of further exploration.