The repeatability of three methods for measuring prospective patients' values in the context of treatment choice for end-stage renal disease

In the context of the choice of treatment for end-stage renal disease (ESRD ), three approaches to value assessment were examined for their repeatabili ty over time within subjects. If formal decision analyses are to be used to advise patients about treatment choice, then repeatable value assessment m ethods, an essential component of such analyses, are needed. The methods as sessed were standard gamble (SG), time trade-off (ITO), and visual analogue (VA). Sixty-six nephrology clinic patients were interviewed on two occasio ns, 10 days apart, by one of two interviewers. An information session was c onducted 1 week before the first interview. Subjects were taught about the treatments using an information package developed expressly for the study a nd a video produced by a pharmaceutical company for use in this decision co ntext. Patients differed widely in the values provided for the various trea tments of ESRD, with responses that ranged across the entire scale (0 to 10 0). The repeatability of the three methods was poor, with the coefficients of repeatability (95% range of differences from one occasion to the next) o bserved as +/-21.4 for SG, +/-38.4 for TTO, and +/-36.5 for VA. When subset s defined by characteristics that may have improved the repeatability were analyzed, the magnitude of the error did not vary substantially. The poor r epeatability of these methods raises questions about their use for decision analyses applied to the individual context. J CLIN EPIDEMIOL 52;9:849-860, 1999. (C) 1999 Elsevier Science Inc.