Patient Perception, Preference and Participation
The effect of information on preferences stated in a choice-based conjoint analysis

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Abstract

Objective

The objective of the study was to investigate the effect of a priori information on preferences for treatment elicited in a discrete choice experiment.

Methods

A convenience sample of 100 subjects was randomly split into two groups. The groups received minimal or extensive information on the treatment of ankle and foot impairment in stroke. Then, they participated in a discrete choice experiment. Possible treatment was described using eight decision criteria with two to four levels each. Part-worth utility coefficients for the criteria levels, criteria importance and overall treatment preference were estimated. It was tested whether the amount of information that was received influenced the outcome of the discrete choice experiment.

Results

In the extensively informed group fewer reversals in the expected order of part-worth utilities were found. Criteria importance for four of the eight criteria and criteria importance ranking between the minimally and extensively informed subject groups were significantly different. The difference in part-worth utility of the levels had a minor effect on the predicted utility of the available treatments.

Conclusion

The lower number of level rank reversals in the extensively informed subjects indicates a better understanding of outcome desirability and thus a better understanding of the decision task. The effect of more extensive information on predicted treatment preference was minimal.

Practice implications

While interpreting the results of a discrete choice experiment, the effect of prior knowledge on the decision problem has to be taken into account. Although information seems to increase the understanding of the decision task, outcomes valuation can also be directed by information and more extensive information increases the cognitive burden which is placed on the subjects. Future research should focus on the exact nature and size of the effects and the results of this study should be clinically validated.

Introduction

In recent years, assessment of health care preferences has been promoted in health care decision making [1], [2], [3]. On a macro level, policy makers are interested in the values and preferences of the community to explain or predict the uptake of health care programs [4]. On a micro level the relevance of patient preferences in decision making is put forward in the models of shared and informed decision making [5], [6]. As a result the use and usability of preference elicitation techniques are becoming a domain of interest in health care.

A preference elicitation technique that is often used to evaluate the mode and effect of health care is a conjoint analysis (CA) [7]. A specific form of CA is a discrete choice experiment (DCE). In a DCE a subject is asked to choose the preferred health state, product or service from a set of two or more scenarios. The hypothetical scenarios are constructed from short statements (levels) on the key characteristics (attributes or criteria) of the health state, product or service. A subject is expected to weigh criteria importance and level attractiveness during the decision task. A set of part-worth utilities for the criteria levels is estimated from the observed choices of the subject. A part-worth utility is the value of a criterion level to the subject. More attractive levels have higher part-worth utility. With the part-worth utilities for all levels, the relative importance of decision criteria and the overall preference for treatment can be estimated [8], [9], [10].

In earlier studies some methodological issues were raised with regard to the application of discrete choice experiments [11], [12]. It is known that the framing of the scenarios can influence outcome [12], [13]. However, no previous studies were focused on the effect of a priori information on the outcome of a DCE. This is important, because although information is seen as a prerequisite for decision making, it is known that the order, type and framing of information can influence the way information is used to make real-life decisions [14], [15], [16]. Moreover, it was found that observed treatment preference is influenced by the information that is available to a patient [17]. It is unknown whether preferences elicited in a hypothetical situation, such as a DCE, are also influenced by the information that is available to a subject prior to partaking in the experiment. In DCEs, much attention is focused on the description of the scenarios by ensuring that relevant information is presented in a comprehensible way in the description of criteria levels [9]. It could be hypothesized that as much attention is required to determine how much and which information is presented prior to a DCE, if the outcome of such a study is influenced by the information which is available to a subject.

Therefore, the aim of the current study was to determine if informing subjects with the actual harms and benefits of treatment and the available treatment options in an informational brochure before participating in a DCE influences its outcome, i.e., the part-worth utilities of criteria levels, the importance of decision criteria, and the predicted preference for treatment.

The decision context in the study was the treatment of ankle and foot impairment in stroke. In stroke, a deviant position of the ankle and foot that hinders standing and walking is a common disability. Determining the best treatment in ankle and foot impairment is a value-based decision, as the evidence of the effect of the treatment alternatives on patient performance is limited [18], [19]. Surgical, technological and orthotic treatment alternatives are available, which differ widely in terms of impact of treatment to the patient, in comfort and cosmetics, and in the required use of walking aids or braces during and post-treatment. This makes the decision for treatment in ankle and foot impairment extremely suitable for a trading exercise such as a DCE.

Section snippets

Study design and procedure

The study was reviewed by the Human Subjects Ethics Review Board of the Roessingh Centre for Rehabilitation and was exempted from formal approval because it was a onetime experiment without emotional impact to subjects. A convenience sample of 80 bachelors and master students and 20 colleagues in the research department was approached for the study and agreed to participate. All subjects were familiar with health research, as they were involved in a health research project or in a health

Part-worth utilities

Some differences were found in the ranking of criteria and the order of criteria levels between the two groups (Table 1). The order of preference of the part-worth utilities in the criteria with a natural order was as expected for criterion 8 (“success rate”) in both groups. However, the expected order of preference was violated for criterion 1 in both groups and for criterion 5 in the minimally informed group (Table 1).

In the criteria with an expectation on order which was based on common

Discussion

In the current study significant differences in preference estimates were found between two groups of subjects. Preference differences were mainly observed in part-worth utilities. It seems that more extensive information resulted in a: (1) decrease in level order reversals in the criteria with a natural order; (2) higher acceptance of negative treatment aspects in favor of a more positive treatment result and (3) higher preference for ready-made shoes at the cost of ankle stability.

We

Acknowledgements

This research was supported by The Netherlands Organization for Health Research and Development ZonMw (grant number 143.50.026) and the VIDI-award to AM Stiggelbout of The Netherlands Organization for Scientific Research NWO Innovational Research Incentives (grant number 917.56.356). We would like to thank Rudolf de Ruiter for his contribution to this study and the reviewers of the manuscript for their valuable comments that helped to improve the quality of the manuscript.

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