SHOULD VALUE CLARIFICATION EXERCISES IN DECISION AIDS ENCOURAGE COMPENSATORY STRATEGIES?

Purpose: Conventional decision aids (DAs) typically ask subjects to clarify and communicate their personal values through unconstrained exercises where the importance of features associated with alternatives are rated independently of each other. This study compares the results of an unconstrained exercise to a constrained exercise that explicitly requires subjects to trade-off between different features.

Methods: The study population comprised of patients with Rheumatoid Arthritis who completed a novel online video based DA aimed to facilitate informed decision making regarding the use of methotrexate therapy. The value clarification exercise asked respondents to consider the importance of improving joint pain, joint damage, physical function, avoidance of side effects, becoming pregnant and drinking alcohol. Patients were randomly allocated to a conventional rating scale followed by a constrained exercise (constant sum) or vice versa. Intra-subject agreement across both exercises was tested using Kendall tau distance (ordinal concordance) and Dirichlet (cardinal concordance).

Results: We recruited 31 subjects (77% were female, mean age of 54 (SD=14.6)). Two subjects failed to complete the exercise. Features deemed most important to patients in both exercises were ‘improving joint pain and damage’, and ‘physical function’. However, the conventional exercise found these features to be equally important, while the constrained exercise discerned joint damage to be slightly more important. Based on cardinal tests, the values on all features between exercises differed by statistically significant amounts with the exception of ‘becoming pregnant’. On ordinal tests, a mean Kendall tau of 0.22 suggested only moderate agreement between exercises.

Conclusions: In most situations for which DAs are designed, subjects must adopt compensatory strategies where all the information is combined together and so a negative feature for one alternative can be ‘compensated’ for by a positive feature for another. A concern is that conventional value clarification exercises do not encourage this compensatory decision making. As such the nature of the task may result in expressing preferences that do not reflect patient’s true values but rather are shaped by the exercise undergone to formulate them. Our findings suggest some support for this proposition. Various constrained trade-off value clarification exercises are available, but differ in their complexity, time to complete and underlying theory. Further research on the optimal value clarification exercise should be undertaken.