iMPACT3: Internet-based development and administration of utility elicitation protocols.

iMPACT3 (Internet Multimedia Preference Assessment Instrument Construction Tool, version 3) is a software development environment that helps researchers build Internet-capable multimedia utility elicitation software programs. The program is a free, openly accessible Web site (http.// preferences.ucsd.edu/impact3/asp). To develop a utility elicitation software program using iMPACT3, a researcher selects modular protocol components from a library and custom tailors the components to the details of his or her research protocol. iMPACT3 builds a Web site implementing the protocol and downloads it to the researcher's computer. In a study of 75 HIV-infected patients, an iMPACT3-generated protocol showed substantial evidence of construct validity and good internal consistency (logic error rates of 4% to 10% and procedural invariance error rates of 10% to 28%, depending on the elicitation method) but only fair 3- to 6-week test-retest reliability (intraclass correlation coefficient= 0.42 to 0.55). Further work may be needed on specific utility assessment procedures, but this study's results confirm iMPACT3's feasibility in facilitating the collection of health state utility data.

Acceptability of computerized visual analog scale, time trade-off and standard gamble rating methods in patients and the public.

One technique to enhance patient participation in clinical decision making is formal measurement of preferences and values. Three commonly applied methods are a visual analog scale(VAS), the standard gamble(SG), and the time trade-off(TTO). We studied participants subjective experience using computer implementations these methods using scale we call the VIBE (for Value Instrument Battery--Evaluation) that measures four aspects of user acceptance (clarity, difficulty, reasonableness, and comfort level) Studies were performed in two groups: patients with HIV infection (n=75) and a convenience sample of the general public(n=640). In the patient study, VIBE scores appeared reliable (Cronbach s alpha of 0.739, 0.826, and 0.716, for VAS, SG, and TTO ratings, respectively.) Patients acceptance of the VAS the highest, followed by the TTO and the SG method (p<0.05 for all comparisons). Despite significant enhancements in computer software for measuring SG preferences, observed differences in acceptance between SG and VAS methods were replicated in the general public study (p<0.0001 for differences). The results suggest developers of clinical decision support systems should use VAS and TTO rating methods where these methods are theoretically appropriate.