Automated computer interviews to elicit utilities: potential applications in the treatment of deep venous thrombosis

Abstract

Objective: To assess the practicality of an automated computer interview as a method to assess preferences for use in decision making. To assess preferences for outcomes of deep vein thrombosis (DVT) and its treatment.

Study design: A multimedia program was developed to train subjects in the use of different preference assessment methods, presented descriptions of mild post-thrombotic syndrome (PTS), severe PTS and stroke and elicited subject preferences for these health states. This instrument was used to measure preferences in 30 community volunteers and 30 internal medicine physicians. We then assessed the validity of subject responses and calculated the number of quality-adjusted life years (QALYs) for each individual for each alternative.

Results: All subjects completed the computerized survey instrument without assistance. Subjects generally responded positively to the program, with volunteers and physicians reporting similar preferences. Approximately 26.5% of volunteers and physicians had preferences that would be consistent with the use of thrombolysis. Individualization of therapy would lead to the most QALYs.

Conclusions: Utilization of computerized survey instruments to elicit patient preferences appears to be a practical and valid approach to individualize therapy. Application of this method suggests that there may be many patients with DVT for whom treatment with a thrombolytic drug would be optimal.

Figure 1

Standard Gamble preference assessment method. The Standard Gamble is the index method to measure preferences for health conditions. To measure a patient's values for a health condition using this method, the assessor assists the patient with determining the probability P where the patient is indifferent between two alternatives: (1) living the remainder of his or her life with some health condition; and (2) a gamble with P probability of normal life coupled with 1 - P probability of immediate death.

Figure 2

Multimedia computer-based implementation of the Visual Analog Scale. The scale uses a double anchored scale with death at the bottom and perfect health at the top. An illustration of severe post-thrombotic syndrome is also shown. Subjects can click anywhere on the scale to provide their ratings for quality of life. They can adjust the level by dragging the level up and down using the mouse pointer.

Figure 3

Multimedia computer-based implementation of the Standard Gamble (SG). To make the SG preference elicitation task as similar as possible to the types of decisions that patients ordinarily face, we used real-life scenarios and a visual representation of the levels of risk patients may encounter through treatment. The SG utility for a health condition is approximately one minus this maximum acceptable risk of death. This picture shows a point early in the assessment process at which the computer is determining if a patient would take a small risk of death to avoid life with post-thrombotic syndrome.

Figure 4

User acceptance of the program. The SG preference assessment requires patients to contemplate their own mortality; this can be an unpleasant experience for some people. At the end of the computer interview, subjects were asked to evalute the experience using this program on a five-point Likert-type scale (Very Positive, Generally Positive, Positive and Negative, Generally Negative, and Very Negative). More than 90% of subjects described the experience of using the program as generally positive or very positive despite the potentially unpleasant nature of the tasks required during the computer interview.